Alkaline Mineralization Research Articles

Ocean alkalinity enhancement – avoiding runaway CaCO3precipitation during quick and hydrated lime dissolution

Abstract. Ocean alkalinity enhancement (OAE) is a method that can remove carbon dioxide (CO2) from the atmosphere and counteract ocean acidification through the dissolution of alkaline minerals. Currently, critical knowledge gaps exist regarding the dissolution of different minerals suitable for OAE in natural seawater. Of particular importance is to understand how much alkaline mineral can be dissolved before secondary precipitation of calcium carbonate (CaCO3) occurs, since secondary CaCO3 precipitation reduces the atmospheric CO2 uptake potential of OAE. Using two types of mineral proposed for OAE, quick lime (CaO) and hydrated lime (Ca(OH)2), we show that both (<63 µm of diameter) dissolved in seawater within a few hours. No CaCO3 precipitation occurred at a saturation state (ΩA) of ∼5, but CaCO3 precipitation in the form of aragonite occurred above an ΩA value of 7. This limit is lower than expected for typical pseudo-homogeneous precipitation, i.e. in the presence of colloids and organic matter. Secondary precipitation at low ΩA (∼ 7) was the result of heterogeneous precipitation onto mineral surfaces, most likely onto the added CaO and Ca(OH)2 particles. Most importantly, runaway CaCO3 precipitation was observed, a condition where significantly more total alkalinity (TA) was removed than initially added. Such runaway precipitation could reduce the OAE CO2 uptake efficiency from ∼ 0.8 mol of CO2 per mole of added TA down to 0.1 mol of CO2 per mole of TA. Runaway precipitation appears to be avoidable by dilution below the critical ΩA threshold of 5, ideally within hours of the mineral additions to minimise initial CaCO3 precipitation. Finally, OAE simulations suggest that for the same ΩA threshold, the amount of TA that can be added to seawater would be more than 3 times higher at 5 ∘C than at 30 ∘C. The maximum TA addition could also be increased by equilibrating the seawater to atmospheric CO2 levels (i.e. to a pCO2 of ∼ 416 µatm) during addition. This would allow for more TA to be added in seawater without inducing CaCO3 precipitation, using OAE at its CO2 removal potential.

Effects of alkaline mineral complex water supplementation on growth performance, inflammatory response, and intestinal barrier function in weaned piglets.

The purpose of the present study was to investigate the effects of drinking water alkaline mineral complex (AMC) supplementation on growth performance, intestinal morphology, inflammatory response, immunity, antioxidant defense system, and barrier functions in weaned piglets. In a 15-d trial, 240 weaned piglets (9.35 ± 0.86 kg) at 28 d of age (large white × landrace × Duroc) were randomly divided into two groups: the control (Con) group and the AMC group. Drinking water AMC supplementation improved (P < 0.01) final body weight (BW) and average daily gain (ADG) in weaned piglets compared to the Con group. Importantly, AMC reduced (P < 0.01) the feed-to-gain (F:G) ratio. AMC water improved the physical health conditions of piglets under weaning stress, as reflected by the decreased (P < 0.05) hair score and conjunctival score. Moreover, there was no significant (P > 0.05) difference in relatively small intestinal length, organ (liver, spleen, and kidney) indices, or gastrointestinal pH value in weaned piglets between the two groups. Of note, AMC significantly promoted the microvilli numbers in the small intestine and effectively ameliorated the gut morphology damage induced by weaning stress, as evidenced by the increased (P < 0.05) villous height (VH) and ratio of VH to crypt depth. Additionally, AMC lessened the levels of lipopolysaccharide (LPS, P < 0.01) and the contents of IL1β (P<0.05), and TNF-α (P<0.05) in the weaned piglet small intestine. Conversely, the gut immune barrier marker, secretory immunoglobulin A (sIgA) levels in serum and small intestine mucosa were elevated after AMC water treatment (P < 0.01). Furthermore, AMC elevated the antioxidant mRNA levels of (P < 0.05) SOD 1-2, (P < 0.01) CAT, and (P < 0.01) GPX 1-2 in the small intestine. Likewise, the mRNA levels of the small intestine tight junction factors Occludin (P < 0.01), ZO-1 (P < 0.05), Claudin 2 (P < 0.01), and Claudin 5 (P<0.01) in the AMC treatment group were notably higher than those in the Con group. In conclusion, drinking water AMC supplementation has an accelerative effect on growth performance by elevating gut health by improving intestinal morphology, the inflammatory response, the antioxidant defense system, and barrier function in weaned piglets.

Insights into the interaction between typical amines and alkaline minerals for improved CO2 absorption and mineralization

AbstractAmine scrubbing is a mature technology to cut down CO2 emissions from human activities but suffers from a high energy consumption of solvent regeneration. The integrated CO2 absorption and mineralization (IAM) process can effectively reduce the energy consumption of amine regeneration by replacing traditional thermal regeneration with chemical regeneration via CO2 mineralization. However, a fundamental understanding of the interaction between typical amines and alkaline minerals was still lacking. In this paper, the effects of amine types on amine regeneration, alkaline metal leaching, and CaCO3 precipitation during the IAM process were explored by using five typical amines and Ca(OH)2/Mg(OH)2. Results showed very different regeneration kinetics and efficiencies were observed in five selected amine solutions, which displayed a decreased performance in the order TEA &gt; MDEA &gt; DEA &gt; AMP &gt; MEA. The regeneration performance was significantly affected by the dissolution of Ca(OH)2/Mg(OH)2 which was inversely proportional to the trend of their pKa values. TEA displayed the largest regeneration efficiency of about 95% by Ca(OH)2 and 83% by Mg(OH)2, which was much larger than other amines reported in the open literature, due to its lower pKa value than other selected amines. More interestingly, the particle size of CaCO3 produced from amine solutions was smaller than that from CaCl2 solution reported in the literature. There was a rough linear relationship between CaCO3 particle size and amine pKa values. TEA induced the formation of nano scaled CaCO3, which might be attributed to the adsorbing of TEA on the CaCO3 crystal and inhibiting the crystal growth. © 2022 Society of Chemical Industry and John Wiley &amp; Sons, Ltd.

Geochemical Negative Emissions Technologies: Part I. Review

Over the previous two decades, a diverse array of geochemical negative emissions technologies (NETs) have been proposed, which use alkaline minerals for removing and permanently storing atmospheric carbon dioxide (CO2). Geochemical NETs include CO2 mineralization (methods which react alkaline minerals with CO2, producing solid carbonate minerals), enhanced weathering (dispersing alkaline minerals in the environment for CO2 drawdown) and ocean alkalinity enhancement (manipulation of ocean chemistry to remove CO2 from air as dissolved inorganic carbon). CO2 mineralization approaches include in situ (CO2 reacts with alkaline minerals in the Earth's subsurface), surficial (high surface area alkaline minerals found at the Earth's surface are reacted with air or CO2-bearing fluids), and ex situ (high surface area alkaline minerals are transported to sites of concentrated CO2 production). Geochemical NETS may also include an approach to direct air capture (DAC) that harnesses surficial mineralization reactions to remove CO2 from air, and produce concentrated CO2. Overall, these technologies are at an early stage of development with just a few subjected to field trials. In Part I of this work we have reviewed the current state of geochemical NETs, highlighting key features (mineral resources; processes; kinetics; storage durability; synergies with other NETs such as DAC, risks; limitations; co-benefits, environmental impacts and life-cycle assessment). The role of organisms and biological mechanisms in enhancing geochemical NETs is also explored. In Part II, a roadmap is presented to help catalyze the research, development, and deployment of geochemical NETs at the gigaton scale over the coming decades.

The Carbon-Capture Efficiency of Natural Water Alkalinization: Implications For Enhanced weathering

Enhanced weathering (EW) is a promising negative-emission technology that artificially accelerates the dissolution of natural minerals, promotes biomass growth, and alleviates the acidification of soils and natural waters. EW aims to increase the alkalinity of natural waters (alkalinization) to promote a transfer of CO2 from the atmosphere to the water. Here we provide a quantification of the alkalinization carbon-capture efficiency (ACE) as a function of the water chemistry. ACE can be used for any alkaline mineral in various natural waters. We show that ACE strongly depends on the water pH, with a sharp transition from minimum to maximum in a narrow interval of pH values. We also quantify ACE in three compartments of the land-to-ocean aquatic continuum: the world topsoils, the lakes of an acid-sensitive area, and the global surface ocean. The results reveal that the efficiency of terrestrial EW varies markedly, from 0 to 100 %, with a significant trade-off in acidic conditions between carbon-capture efficiency and enhanced chemical dissolution. The efficiency is more stable in the ocean, with a typical value of around 80 % and a latitudinal pattern driven by differences in seawater temperature and salinity. Our results point to the importance of an integrated hydrological and biogeochemical theory to assess the fate of the weathering products across the aquatic continuum from land to ocean.

Surface Free Energy of Titanium Disks Enhances Osteoblast Activity by Affecting the Conformation of Adsorbed Fibronectin

This study evaluated the influence of surface free energy (SFE) of titanium disks on the adsorption and conformation of fibronectin (FN) and the biological behavior of osteoblasts cultured on the FN-treated modified surfaces. High [H]-SFE titanium disks were irradiated by a 30 W UV light, while low (L)-SFE titanium disks received no treatment. The surface characteristics of the titanium disks were examined using scanning electron microscope, optical surface profilometer, X-ray photoelectron spectroscopy, and contact angle measurements. Adsorbed FN on different groups was investigated using attenuated total reflection-Fourier transform infrared spectroscopy. MG-63 cells were cultured on FN-treated titanium disks to evaluate the in vitro bioactivity. The experiment showed H-SFE titanium disks adsorbed more FN and acquired more ß-turn content than L-SFE group. MG-63 cells cultured on FN-treated H-SFE titanium disks showed better osteogenic responses, including adhesion, proliferation, alkaline phosphatase activity and mineralization than that on FN-treated L-SFE titanium disks. Compared to L-SFE titanium disks, integrin-β1, integrin-α5 and Rac-1 mRNA levels were significantly higher in MG-63 cells on FN-treated H-SFE after 3 h of culture. These findings suggest that the higher SFE of H-SFE compared to L-SFE titanium disks induced changes in the conformation of adsorbed FN that enhanced the osteogenic activity of MG-63 cells.

Geochemistry of Formation Water and Its Implications for Petroleum Source Rocks in the Fengcheng Formation, Mahu Depression, Xinjiang, China

Geochemical properties of formation water reflect the sedimentary environments and the sealing conditions of the formation, which are of great significance for oil and gas exploration. In this research, the formation waters in the deep Permian Fengcheng Formation in the Mahu Depression were studied by analysis of chemical composition, stable isotopes, and the homogenization temperatures and salinities of fluid inclusions. The results show that the formation water is NaHCO3-type with high salinity, high HCO3-, low concentrations of Ca2+ and Mg2+ and high pH. The overall sealing of the formation is well maintained. Na2SO4-type water was found in some places with poor preservation of oil and gas. The fluid geochemistry and alkaline mineral distribution in the strata, which are dominated by deep fine-grain mixed deposits, indicate that the main body of the Fengcheng Formation was deposited in an alkaline lake sedimentary environment. The isotopic signatures are characterized by high δ13C, negative δ18O, and light strontium and heavy boron isotopes in the strata near the deep fault zone, which indicate that the Fengcheng formation may have been affected by deep hydrothermal fluids. From the first member to the third member of the formation, the salinity first increases and then decreases. This low-high-low trend corresponds to the initial stage of alkaline lake development followed by strong alkali formation and a final stage of water retreat. The coincidence between the spatial distribution of alkaline minerals, high-salinity formation water and source rocks indicates that the alkaline lake environment can form high-quality source rocks with good petroleum generation capacity.

Pre-culturing soil microbial inoculum in plant residues enhanced the resilience of tolerant bacteria and bioneutralization efficacy in alkaline bauxite residues

Bioneutralization of alkaline bauxite residues (BR) may be achieved through in situ organic acids produced from fermentative decomposition of carbohydrates-rich organic matters (e.g., plant residues), which are driven by organophilic and heterotrophic prokaryotes tolerant of extremely saline and alkaline conditions. The present study investigated if the resilience of tolerant prokaryotes in soil microbial inoculums could be improved by pre-culturing them in carbohydrate-rich plant residues, leading to enhanced bioneutralization efficacy in strongly alkaline BR. In a 2-week microcosm experiment with BR (pH ~ 10.5), it was found that the resilience of prokaryotic communities and their functional modules and bioneutralization efficacy were significantly boosted in BR admixed with plant residues (i.e., SM: sugarcane mulch, LH: Lucerne hay) pre-cultured with soil microbial inoculum. The results showed that 10–20% of the initially inoculated soil prokaryotic features were recovered in treatments with pre-cultured plant residues. Besides, the enriched diverse prokaryotes formed highly clustered networks in the amended BR. These modules actively drove C and N mineralization and sustained 0.8–2.0 units of pH reduction, despite the buffering effects of alkaline minerals in BR solid phase. In contrast, soil microbial inoculation cultured in the growth medium lost >99% of the original prokaryotic features in soil inoculums, resulting in merely 0.2–0.7 unit pH reduction in the treated BR. Therefore, pre-culturing soil inoculum in plant residues would be preferred as an integral system to treat BR for effective bioneutralization.

Feasibility and mechanism of an amine-looping process for efficient CO2 mineralization using alkaline ashes

• Amines significantly improved the CO 2 sequestration capacity of ashes. • Amines enhanced Ca 2+ leaching from alkaline ashes. • The phytotoxicity of alkaline ashes were significantly reduced after carbonation. Amine-looping-based CO 2 mineralization is a promising technology for simultaneous CO 2 absorption, mineralization, and carbonate crystallization in a single step. This paper performed a detailed investigation of the feasibility and underlying mechanism of the amine-looping process using industrial alkaline solid wastes, including one Biomass ash (BA) and two coal-fired fly ashes named FA1 and FA2. The CO 2 sequestration capacity and CO 2 removal efficiency of selected ashes were investigated in five typical amine solutions, including monoethanolamine (MEA), diethanolamine (DEA), triethanolamine (TEA), 2-amino-2-methy-1-propanol (AMP), and piperazine (PZ). The physicochemical property of ashes before and after carbonation and the dissolution of alkaline minerals in various amine solutions were systematically determined to explore the underlying mechanism involved in the amine-looping process. Results show that greater improvement in CO 2 removal efficiencies and CO 2 sequestration capacities were obtained by selected ashes in amine solutions compared to the traditional CO 2 mineralization in the water-ash-CO 2 system. It also revealed that amines played important roles in promoting CO 2 mass transfer, enhancing Ca 2+ leaching, and producing small-sized CaCO 3 . The largest CO 2 sequestration capacity (102.9 g/kg) was achieved by FA1 in PZ solution which was suggested as the preferred solvent for the amine-looping process. In addition, the environmental risk of carbonated ashes for agricultural application in terms of amine loss and phytotoxicity was evaluated. Results implied that the phytotoxicity of carbonated BA could be neglected when a simple centrifugal wash was used to remove the absorbed amine on the surface of carbonated BA whilst the phytotoxicity of selected ashes can be significantly reduced after carbonation reactions.

Significant contribution of haloalkaliphilic cyanobacteria to organic matter in an ancient alkaline lacustrine source rock: A case study from the Permian Fengcheng Formation, Junggar Basin, China

Alkaline lakes are productive aquatic environments, and related source rocks appear to possess considerable hydrocarbon generation potential. The Fengcheng Formation (Fm.) source rock is a good case to investigate organic matter enrichment and hydrocarbon generation characteristics of such alkaline lacustrine source rocks. However, the biological contributor to organic matter of the Fengcheng Fm. is generally controversial. Based on geochemical, biological, and theoretical evidence, a new understanding of the biological contributors to organic matter of alkaline lacustrine source rocks was reassessed. The depositional paloenvironment of the Fengcheng Fm. was reconstructed and compared to the Tumbiana Fm. (a typical alkaline lake case) by using alkaline minerals, trace elements, nitrogen isotopes, and biomarkers. The results of abundant alkaline minerals, Pr/Ph < 1, Sr/Ba > 1, B/Ga > 7, gammacerane index >0.2, and δ15N > 10‰ (published data) show that the Fengcheng Fm. was deposited in a reducing, hypersaline, alkaline lake, similar to that of the Tumbiana Fm. The biological contribution to organic matters of the Fengcheng Fm. was comprehensively investigated by biomarkers, fossils, and microbial community structure analysis. The low terrigenous/aquatic ratio, abundant 2-methylhopanes, and high αααC29cholestane-20R proportion of the Fengcheng Fm. provide geochemical evidence for a larger cyanobacteria input than land plants and algae. Identified stromatolites and Chroococcus fossils provide biological evidence for the active participation of cyanobacteria during deposition. The investigation of microbial community structures of modern alkaline lakes provides a theoretical evidence for the fact that cyanobacteria are the dominant phytoplankton in alkaline lakes. The dominance of cyanobacteria in alkaline lakes relates to the following aspects: the extreme resistance of cyanobacteria, their inorganic carbon-concentrating mechanism, their adequate sodium and carbon supply from alkaline lake water, and the inhibited growth of some species of algae within alkaline waters. In summary, haloalkaliphilic cyanobacteria are the primary contributors to organic matter of the Permian Fengcheng Fm. that was deposited in an ancient alkaline lake.

Conversion of alkaline characteristics of bauxite residue by mechanical activated pretreatment: Implications for its dealkalization

Following the strict environmental policies of various countries, the strong alkalinity of bauxite residue (BR) has become a worldwide problem limiting the sustainable development of the global alumina industry. Continuous conversion of solid-phase alkalinity to free alkali is a major challenge for BR dealkalization to reduce its environmental impact. This work aimed to investigate the effect of mechanical grinding pretreatment on the transformation mechanisms of alkaline solids to free alkali at the BR interface under acids leaching, by monitoring the morphology, phase, and speciation transformations of Al and Si using primarily cross-section scanning electron microscopy−energy dispersive X-ray spectroscopy (SEM-EDS) elemental mapping, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The results indicated that particle grinding wrapped some of the alkaline minerals inside the particles to inhibit its release process. The leaching kinetics revealed the order of the buffering effect of minerals against acids leaching is firstly dissolved by minerals containing Na and Ca via the ion-exchange process, followed by Si and Al through the hydrolysis of the desilicated products. The mineral dissemination characteristics and surface compositions further confirmed the undissolved minerals block the interface reaction between embedded alkaline solids and acids to result in the difficult reaction dissolution of alkaline minerals, which is induced by ball milling. This novel approach provides new insight into the efficient dealkalization of BR on a large scale in the industry.

Chronic Sub-Clinical Systemic Metabolic Acidosis - A Review with Implications for Clinical Practice.

When arterial serum pH remains near the lower pH limit of 7.35 for protracted periods of time, a low-grade, sub-clinical form of acidosis results, referred to in this review as chronic, sub-clinical, systemic metabolic acidosis (CSSMA). This narrative review explores the scientific basis for CSSMA, its consequences for health, and potential therapeutic interventions. The major etiology of CSSMA is the shift away from the ancestral, alkaline diet which was rich in fruit and vegetables, toward the contemporary, acidogenic 'Westernized' diet characterized by higher animal protein consumption and lack of base forming minerals. Urine pH is reduced with high dietary acid load and may be a convenient marker of CSSMA. Evidence suggests further that CSSMA negatively influences cortisol levels potentially contributing significantly to the pathophysiology thereof. Both CSSMA and high dietary acid load are associated with the risk and prognosis of various chronic diseases. Clinical trials show that CSSMA can be addressed successfully through alkalizing the diet by increasing fruit and vegetable intake and/or supplementing with alkaline minerals. This review confirms the existence of a significant body of evidence regarding this low-grade form of acidosis as well as evidence to support its diverse negative implications for health, and concludes that CSSMA is a condition warranting further research.

Treatment of laryngeal pathology associated with gastroesophageal reflux disease

To increase the effectiveness of the treatment of laryngeal pathology associated with gastroesophageal reflux disease (GERD), to determine the indications for the appointment of anti-inflammatory therapy to these patients. 120 patients were examined and treated, 58 of them men and 62 women, aged 30 to 82 years with GERD-associated laryngeal pathology. Three groups of patients were formed, comparable in age and gender, in accordance with the type of pachydermia in interarytenoid region; type 1 (40 patients) - pachydermia did not go beyond the middle of the interarytenoid cartilage (according to G.F. Ivanchenko), less than 3 mm, without signs of perifocal inflammation; type 2 (40 patients) - pachydermia of large size, extending beyond the middle of the interarytenoid cartilage with a spread to the entire interarytenoid region (according to G.F. Ivanchenko), often in combination with hyperkeratosis or epithelial dysplasia; type 3 (30 patients) - pachydermia of large size in combination with severe perifocal inflammation. All patients received antireflux therapy. Each group is divided into two subgroups: patients who did not receive anti-inflammatory therapy, and patients who received anti-inflammatory therapy, the basis of which was inhalation with degassed alkaline mineral water, as well as according to indications acetylcysteine, benzyldimethylammonium chloride 0.01% or hydroxymethylquinoxalindioxide, with severe swelling of the mucous membrane - budesonide. All patients completed the questionnaire "Reflux Symptoms Scale" before and after treatment. In group 2 patients (with type 2 pachydermia), the effectiveness of anti-inflammatory therapy was 75%. Of the 20 patients in this group, after inhaled therapy, 4 patients had pachydermia in interarytenoid region disappeared, 11 patients had type 1 pachydermia visualized, 5 (25%) patients had no pronounced dynamics. In group 3 patients (with type 3 pachydermia), the effectiveness of inhaled treatment was 100%, out of 15 patients after inhaled therapy, type 2 pachydermia was diagnosed in 8 patients, type 1 pachydermia - in 7 patients. In 4 patients, complex therapy led to the complete disappearance of reflux-associated laryngeal granulomas without surgical treatment. The effectiveness of inhaled therapy in relation to patient complaints after a month was 87%, while the effectiveness of treatment of patients without inhalation was 45%. Indications for the appointment of inhaled anti-inflammatory therapy in patients with reflux-associated pathology of the larynx are the presence of complaints of hoarseness, dryness, tickling, lump in the throat and chronic cough, endolaryngoscopic signs of exacerbation of chronic inflammation of the mucous membrane of the posterior larynx.

Preparation of ball-milled phosphorus-loaded biochar and its highly effective remediation for Cd- and Pb-contaminated alkaline soil

Pyrolytic biochar is a good material for remediating soils contaminated with heavy metals; however, it exhibits strong alkalinity, which easily causes soil alkalization and fertility reduction. Herein, a series of novel biochar materials (BPBCs) were prepared by combined ball milling and phosphorus (P)-loading. The optimized BPBC were fabricated in the basis of Cd and Pb adsorption capacities of the biochar, with pyrolysis at 700 °C, ball milling for 12 h and the addition of 5% red P (BPBC700). Ball milling could effectively grind pristine biochar into submicron particles and nanoscale P particles could be uniformly loaded on BPBC700. Moreover, the oxidative conversion of red P into phosphorus oxides, phosphoric acid and (hydro)phosphates was promoted due to reactions with the carbonates, alkaline minerals and O-containing functional groups of biochar. These reactions also decreased the biochar and soil pH to nearly neutral by acid-base neutralization. Pot experiments showed that BPBC700 had better effects than the pristine or ball-milled biochar in improving soil properties (e.g., cation exchange capacity and organic carbon), increasing the concentrations of soil nutrients (e.g., N and P), promoting alkaline phosphatase, catalase and urease activities, decreasing soil mobility and plant accumulation of Cd and Pb, and alleviating Cd and Pb stress on maize plants. Thus, BPBC is a promising and ecofriendly amendment to enhance its adsorption ability on Cd and Pb, soil quality and plant productivity in contaminated soil.

Accelerated Weathering and Carbonation (Mild to Intensified) of Natural Canadian Silicates (Kimberlite and Wollastonite) for CO2 Sequestration

Canada’s mineral reserves can play a very important role in curbing climate change if natural alkaline minerals are used for the process of mineral carbonation. In this work, the potential of using two Canadian natural silicates for accelerated carbonation is experimentally assessed: kimberlite mine tailing (Mg0.846Al0.165Fe0.147Ca0.067SiO3.381) from the Northwest Territories, and mined wollastonite ore (Ca0.609Mg0.132Al0.091Fe0.024SiO2.914) from Ontario. The aim of this work was to evaluate the weathering reactivity and CO2 uptake capacity via carbonation of these two comminuted rocks, both of which are made up of a mixture of alkaline minerals, under process conditions that spanned from milder to intensified. Research questions addressed include: does kimberlite contain a sufficient amount of reactive minerals to act as an effective carbon sink; is dehydroxylation necessary to activate kimberlite, and to what extent does it do this; do secondary phases of wollastonite hinder its reactivity; and can either of these minerals be carbonated without pH buffering, or only weathered? Incubator, slurry, and pressurized slurry methods of accelerated weathering and carbonation were used, and the effect of the process parameters (temperature, solid-to-liquid ration, reaction time, CO2 level, pH buffer) on the CO2 uptake and crystalline carbonates formation is tested. The reacted samples were analyzed by pH test, loss-on-ignition test, calcimeter test, and X-ray diffraction analysis. Results showed that wollastonite ore (rich in fast-weathering CaSiO3) is more suitable for accelerated carbonation than kimberlite tailing (containing slow-weathering hydrated magnesium silicates and aluminosilicates) when only its capability to rapidly form solid carbonates is considered. Incubator and pressurized buffered slurry methods proved to be most effective as under these conditions the precipitation of carbonates was more favorable, while the unbuffered slurry reaction conditions were more akin to accelerated weathering rather than accelerated carbonation.

Effects of Additives on Coke Reactivity and Sulfur Transformation during Co-pyrolysis of Long Flame Coal and High-Sulfur Coking Coal.

A silica-aluminum-based mineral (GL) was selected for inspecting the effects of interactions of minerals in coal blends on the coke reactivity index (CRI) and sulfur transformation during co-pyrolysis of long flame coal and high-sulfur coking coal. Results indicate a good compatibility for the supply of active hydrogen, decomposition of sulfur, and regulation of reactivity. The experimental values of sulfur content in different coal blend cokes are lower than the calculated values, which can be determined as a result of the directional regulation effect of long flame coal on sulfur transformation. The addition of GL in coal blends significantly reduces the CRI of the corresponding coke, and the effect of GL on coke reactivity is also verified by a 10 kg coke oven experiment. When increasing the ratio of long flame coal, the sulfur fixation in the solid phase has a tendency to be enhanced by alkaline minerals. Also, GL plays a role in reducing the capture of sulfur free radicals by alkaline minerals, which improves the sulfur removal during pyrolysis of coal blends and then reduces the sulfur content in coke. This work provides a reference for using silica-aluminum-based minerals to reduce the capture of sulfur and catalytic effect on coke reactivity.

Carbonation of EAF Stainless Steel Slag and Its Effect on Chromium Leaching Characteristics

EAF stainless steel slag (EAF slag) is one kind of chromium-bearing metallurgical solid waste, which belongs to alkaline steel slag, and contains a large number of alkaline mineral phases. The carbonation activity of these minerals gives EAF slag the capability to effectively capture CO2. In this paper, EAF slag samples with different carbonation degrees were prepared by the slurry-phase accelerated carbonation route. The mineralogical identification analysis was used to qualitatively and semi-quantitatively determine the types and contents of the carbonatable mineral phases in the EAF slag. The sequential leaching test was used to study the chromium leachabilities in EAF slags with different carbonation degrees. The results showed that the main minerals with carbonation activity in EAF slag were Ca3Mg(SiO4)2 and Ca2SiO4, with mass percentages of 56.9% and 23%, respectively. During the carbonation process, Ca2SiO4 was the main reactant and calcite was the main product. As the degree of carbonation increased, the pH of the EAF slags’ leachate gradually decreased while the redox potential (Eh) gradually increased. At the same time, a large amount of Ca2+ in the EAF slag combined with CO2 to form slightly soluble calcium carbonate, which led to a significant decrease in the conductivity of the leachate. With the gradual increase in carbonation ratio, the leachability of chromium in the EAF slag first decreased and then increased, and reached its lowest value when the CO2 uptake ratio was 11.49%.

Inter-annual reduction in rice Cd and its eco-environmental controls in 6-year biannual mineral amendment in subtropical double-rice cropping ecosystems

The alkaline mineral amendment is a practical means of alleviating Cd concentration in rice grain (CdR) in the short-term; however, the long-term remediation effect of mineral amendment on the CdR and the eco-environmental controls remains unknown. Here a mineral (Si–Ca–Mg) amendment, calcined primarily from molybdenum tailings and dolomite, was applied biannually over 6 years (12 seasons) to acidic and moderately Cd-contaminated double-rice cropping ecosystems. This study investigated the inter-annual variation of Cd in the rice-soil ecosystem and the eco-environmental controls in subtropical rice ecosystems. CdR was reduced by 50%–86% following mineral amendment. The within-year reduction in CdR was similar between early rice (50%–86%, mean of 68%) and late rice (68%–85%, mean of 74%), leading to CdR in all early rice and in 83% of late rice samples below the upper limit (0.2 mg kg−1) of the China National Food Safety Standards. In contrast, the inter-annual reduction in CdR was moderately variable, showing a greater CdR reduction in the later 3 years (73%–86%) than in the former 3 years (54%–79%). Three years continuous mineral amendment was required to guarantee the safety rice production. The concentrations of DTPA-extractable and exchangeable Cd fractions in soil were reduced, while the concentration of oxides-bound Cd was increased. In addition, the soil pH, concentrations of Olsen-P and exchangeable Ca and Mg were elevated. These imply a lower apparent phytoavailability of Cd in the soil following mineral amendment. An empirical model of the 3-variable using soil DTPA-Cd, soil Olsen-P, and a climatic factor (precipitation) effectively predicted temporal changes in CdR. Our study demonstrates that Cd phytoavailability in soil (indexed by DTPA-extractable Cd) and climatic factors (e.g., temperature and precipitation) may directly/indirectly control the inter-annual reduction in CdR following mineral amendment in slightly and moderately Cd-contaminated paddy ecosystems.

Pharmacokinetic investigation of branched oligohexamethyleneguanidine hydrochloride in a liquid composition for the treatment of stomatitis and gingivitis

Branched oligohexamethyleneguanidine hydrochloride (branched OHMG-HC) possesses high biocidal activity. This study aimed at evaluating the pharmacokinetics of branched OHMG-HC and is mandatory for obtaining permission to conduct clinical studies. The thermal activation method was used to obtain radioactive-labeled drugs for the investigation of substance distribution in various tissues of experimental animals (rats and rabbits). Substance administration was carried out both orally (a dose was split into two equal volumes that were applied to buccal zones of the oral cavities of the animals) and intravenously to get a clear pharmacokinetic profile. In this research, the drug was applied in the concentration of 0.77 mg/kg with the addition of 0.037 mg/kg 3H-OHMG for rats, and 0.42 mg/kg with the addition of 0.015 mg/kg 3H-OHMG for Chinchilla rabbits. The selected samples of blood, organs, and urine underwent alkaline mineralization. A quantitative determination of 3H-OHMG was carried out using a liquid β-, γ-counter according to the level of scintillation in the sample. Branched OHMG-HC displayed uniform distribution within all main organs and tissues upon oral administration. The highest concentrations were found in liver and kidney tissues, whereas the lowest in blood, cardiac muscle tissue, and brain. The closeness of the fabs values obtained from different animals (24.5% for rats and 29.0% for rabbits) demonstrated the absence of the species specificity in response to the pharmaceutical substance. The main parameters of excretion were established, and the half-life time was estimated to be 15 h.

Hydroxamate-Based Histone Deacetylase Inhibitors as Potential Mediators to Induce Dentine Regeneration by Human Dental Pulp Cell

Human dental pulp cells (hDPCs) have shown their plasticity when treated with the hydroxamate-based histone deacetylase (HDAC) inhibitor members, Trichostatin A (TSA), and suberoylanilide hydroxamic acid (SAHA). However, a comparison of their potency to stimulate odontoblast-like differentiation and mineralization has not been reported. The aim of our study was to confirm and compare these TSA and SAHA effects. Primary hDPCs cultured with/without various TSA or SAHA concentrations were evaluated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT), ALP activity, alizarin red staining, and scratch wound healing assays. The inhibitory effect of TSA and SAHA on inhibiting the activity of HDAC was evaluated by HDAC activity assay. Odontoblast-related gene expression was determined using RT-qPCR. The MTT assay indicated that TSA or SAHA did not affect hDPC viability. TSA or SAHA treatment-induced odontoblast-like differentiation as evidenced by a significant increase in alkaline phosphatase activity and mineral deposition after 400 nM TSA or 1 μM SAHA treatment. A significant increase in nuclear factor I C, kruppel like factor 4, dentin matrix acidic phosphoprotein 1, dentin sialophosphoprotein, collagen type I alpha 1 chain, alkaline phosphatase (ALPL), integrin-binding sialoprotein, bone gamma-carboxyglutamate protein, vascular endothelial growth factor A, and cyclin-dependent kinase inhibitor 1A gene expression analyzed by RT-qPCR, at 24, 72 h, 7, and 10 days of treatment. The activity of HDAC in hDPCs culture was significantly inhibited after 72 h TSA and SAHA treatment. The scratch wound healing assay displayed enhanced cell migration at 72 h after TSA or SAHA treatment. Our findings demonstrated that TSA and SAHA have similar stimulatory effects in inducing HDPC odontogenic differentiation and mineralization and propose another potential use of TSA and SAHA to promote dentin regeneration.