Alkaline Additives Research Articles

Rethinking quantified methods for arsenic speciation and risk in a biowaste hydrothermal liquefaction system

Controversy exists to quantify the fate and speciation of Arsenic (As). We investigated its characteristics by As-containing algae in various pH hydrothermal liquefaction (HTL) system, specifically via two classical methods, i.e. the European Community Bureau of Reference (BCR) and Wenzel's method. Solid residue immobilized 11.23–16.55% of As, and 88.07–82.44% was in aqueous by the pH regulators (e.g., CH3COOH, HCl, and KOH). ICP-MS and XRD analysis revealed that As (V) was converted into As (III) and As (0) in the solid residue, while the As (V) was mainly converted into As (III) in the aqueous phase during HTL. When the classified forms of As in solid residue are compared, Wenzel's method was more appropriate for dividing the bio-availability forms of As, whereas BCR was better for estimating the toxic-potential forms of As. Subsequently, pH regulators raised the risk of As in solid residue associated with the increasing of unstable forms. The amide was hydrolyzed to carboxylic acid with acidic additives, which weakened the reducing environment in the HTL process. In contrast, the amide was hydrolyzed to ammonia with the alkaline additives, which enhanced the reducing environment and increased the risk of As in products. This work provided a new insight in systematically evaluating the risk and speciation of As in HTL.

Effective Extraction of the Al Element from Secondary Aluminum Dross Using a Combined Dry Pressing and Alkaline Roasting Process.

Secondary aluminum dross (SAD) is a hazardous solid waste discharged from aluminum electrolysis and processing and the secondary aluminum industries, which causes severe environmental pollution and public health disasters. The stable presence of the α-Al2O3 and MgAl2O4 phases in SAD makes it difficult for it to be efficiently utilized. A combined dry pressing and alkaline roasting process was proposed for extracting the valuable Al element from SAD. Two alkaline additives (NaOH and Na2CO3) were selected as a sodium source for extracting the aluminum source from SAD in order to perform the thermodynamic analysis and roasting experiments. The phase transition behavior and the leaching performance tests were conducted using X-ray diffraction, scanning electron microscopy, X-ray fluorescence, leaching kinetics and thermal analysis. The recovery of Al and Na reached the values of 90.79% and 92.03%, respectively, under the optimal conditions (roasting temperature of 1150 °C, Na2CO3/Al2O3 molar ratio of 1.3, roasting time of 1 h, leaching temperature of 90 °C, L/S ratio of 10 mL·g−1 and leaching time of 30 min). Meanwhile, the removal efficiency of N and Cl reached 98.93% and 97.14%, respectively. The leaching kinetics indicated that the dissolution of NaAlO2 clinkers was a first-order reaction and controlled by layer diffusion process. The green detoxification and effective extraction of the Al element from SAD were simultaneously achieved without any pretreatments.

Isolation, structure elucidation, and high-performance liquid chromatography quantification of photolytic degradation impurities in acrivastine.

Acrivastine is a second-generation H1-receptor antagonist, and its structure is sensitive to ultraviolet. Four unknown and one reported degradation products can be detected in the ultraviolet radiation solutions of acrivastine. To improve the quality control of acrivastine, the photodegradation impurities were isolated and structurally elucidated. There are four new impurities (1-3 and 5), and one reported compound (4). The isolation strategy was designed as preparative high-performance liquid chromatography using a reversed phase column with volatile acid addition in the mobile phase, combined with preparative thin-layer chromatography using silica gel with alkaline addition in the mobile phase. Using the developed methods, five impurities (1-5) were efficiently purified after two or three chromatography runs with purities > 95%. The structures of compounds 1-5 are elucidated based on spectroscopy analysis of MS, and nuclear magnetic resonance spectroscopy. Using the impurity standard, the high-performance liquid chromatography method was developed and validated. The method was proved to be sensitive, accurate (Recovery% 96.1-107.7%), linear (0.15-0.75 μg/mL, R2 >0.996), robust, and specific, and it was successfully used to determine the degradation impurities of acrivastine and its formulation.

Heavy metal solidification and CO2 sequestration from MSWI fly ash by calcium carbonate oligomer regulation

The efficiencies of heavy metals (HMs) solidification and CO2 sequestration from current municipal solid waste incineration fly ash (MSWI FA) carbonation technology are low, and the reaction conditions are complicated. A novel MSWI FA carbonation treatment, which was carried out under room temperature and pressure and controlled by calcium carbonate oligomers, is proposed. Through orthogonal tests, the reaction time (t), temperature (T), CO2 flow rate (V), magnetic stirring rate (W), and liquid-solid ratio (L) of the MSWI FA carbonation treatment were investigated. The results showed that the five influential factors were W>T>L>t>V, and the optimal parameters were 60 min, 20 °C, 200 ml min−1, 600 rpm and 10 L kg−1 (the carbonation efficiency (CE) was 13.8%). When alkaline additives (NaHCO3 or NaOH) were added, the CE increased to 16.5% and 15.1%, respectively, due to the increase of CO32− ions in the solution. The leaching concentrations of Zn, Pb, Cu, and Ni were greatly reduced in the treated samples, and the solidification efficiency reached to 99.1%, 100.0%, 91.3%, and 95.6%, respectively, because they were converted to carbonates and were adsorbed and wrapped by calcium carbonate polymer. The pores on the surface of the treated sample were reduced, and the particle sizes increased. The pH of the leachate of the treated samples decreased to 9.0–11.5 due to the carbonation reaction. This study provides an effective MSWI FA treatment method that has a highly efficient use of HMs and the potential for CO2 sequestration and resource utilization.

Wastewater alkalinity addition as a novel approach for ocean negative carbon emissions

Anthropogenic CO2 emissions have greatly increased atmospheric CO2 contributing to global warming and leading to ocean acidification (Figure 1). As reflected in the recent IPCC report, the scientific community's consensus is that emissions reductions alone are not sufficient or timely enough to avoid a global warming catastrophe. Thus, negative-carbon-emission technologies are needed to avoid atmospheric CO2 overshoot scenarios and limit global warming to less than 2°C by the end of this century per the Paris Agreement.

Synthesis of hydrophobic Pd-poly(ionic liquid)s with excellent CO2 affinity to efficiently catalyze CO2 hydrogenation to formic acid

The catalytic hydrogenation of carbon dioxide (CO2) into formic acid is among the most important reactions to alleviate global warming and realize the carbon cycle. How to achieve rapid activation of CO2 remains a challenge. In this work, we designed two novel hydrophobic poly(ionic liquid)s (PILs) with a good affinity for CO2. Since the abundant N atoms in the PILs can anchor palladium (Pd) nanoparticles, the designed catalyst can rapidly activate CO2 and H2 simultaneously, thus efficiently catalyzing the hydrogenation of CO2 to formic acid under mild conditions. Due to the synergy from the bis(trifluoromethanesulfonyl)amide anion ([Tf2N−]) with strong hydrophobicity and CO2 affinity and trimethylamine (NEt3) as a low dissociation energy alkaline additive, the resultant Pd/PIL-bip-Tf2N exhibited the best catalytic performance on the hydrogenation of CO2 to formic acid. The TOF value reached 1,190 h−1 in the aqueous solution of NEt3 at 100 °C, 1 h, and a total pressure of 4 MPa. The activation energy and dissociation energy during the catalytic process were calculated by DFT, indicating that the synergistic effect of NEt3 is better than that of other alkaline additives. In addition, the catalytic activity of the catalyst remained stable after several cycling experiments. Based on the obtained results, we proposed a possible reaction pathway. Therefore, PILs have great potential as catalyst carrier material for CO2 hydrogenation.

Effects of harvesting on morphological and biochemical characteristics of microalgal biomass harvested by polyacrylamide addition, pH-induced flocculation, and centrifugation

The effects of microalgae harvesting methods on microalgal biomass quality were evaluated using three species namely the freshwater green alga Chlorella vulgaris, marine red alga Porphyridium purpureum and marine diatom Phaeodactylum tricornutum. Harvesting efficiencies of polyacrylamide addition, alkaline addition, and centrifugation ranged from 85 to 95, 59–92 and 100%, respectively, across these species. Morphology of the harvested cells (i.e. compromised cell walls) was significantly impacted by alkaline pH-induced flocculation for all three species. Over 50% of C. vulgaris cells were compromised with alkaline pH compared to < 10% with polyacrylamide and centrifugation. The metabolic profiles varied depending on harvesting methods. Species-specific decrease of certain metabolites was observed. These results suggest that the method of harvest can alter the metabolic profile of the biomass amongst the three harvesting methods, polyacrylamide addition showed higher harvesting efficiency with less compromised cells and higher retention of industry important biochemicals.

Bio‐oil upgrading via ketonization of carboxylic acids on Na promoted Ca/AlOx catalysts

AbstractKetonization of carboxylic acids is valuable for bio‐oil upgrading and producing bio‐derived chemicals. Ca/AlOx metal oxides with various Ca/Al ratios have been prepared by the low‐cost and natural abundant metals in the process. The addition of alkaline or alkaline‐earth metals could significantly improve the activity of Ca/AlOx catalysts by base‐catalyzed ketonization of carboxylic acids. However, the active sites on alkaline‐metal‐doped Ca/AlOx catalysts are still under debate, and the commercialization of these catalysts often suffers from deactivation in long‐term use. Here Ca(Na)/AlOx catalysts with various Ca/Al molar ratios were prepared and evaluated for the ketonization of acetic acid. Sodium addition resulting in the formation of NaAlO2 has higher basicity than CaO. These strong basic sites could significantly promote the ketonization of acetic acid via the thermal decomposition of carboxylates. The Ca(Na)/AlOx catalyst with NaAlO2 populated on the surface could provide 100% acetone selectivity at the complete conversion of acetic acid at 400°C and exhibit no activity loss after a 400 h reaction, which is the most active and stable catalyst for ketonization reaction hitherto. These Ca(Na)/AlOx catalysts are also stable by adding major bio‐oil model compounds (e.g., phenol) into the reaction mixture, which are promising for future bio‐oil upgrading applications.

Bifunctional Oxidation Catalysis of New Titanium-Silicon Molecular Sieve (HTS-1) Based on the Reaction of Allyl Alcohol and Hydrogen Peroxide

The HTS-1 (Hollow Titanium silicalite molecular sieve) catalyst with bifunctional catalysis showed superior catalytic activity in the epoxidation of olefins and the oxidation of alcohols. The competitive oxidation law of enols in the HTS-1/H2O2 oxidation system was studied. The effects of various reaction conditions, such as the reaction temperature, solvent, catalyst type, and the amount of additive, were examined. The results indicated that the HTS-1 catalyst preferentially catalyzes AA epoxidation to produce glycidol (GLY) efficiently and selectively using polar proton solvent and proper temperature. Using alkaline additives can greatly improve the catalytic activity of HTS-1 and selectivity of glycidol. Under optimal conditions, the conversion of AA can rate to 77%, and the selectivity of GLY can also achieve 91%.

Towards understanding mesopore formation in zeolite Y crystals using alkaline additives via in situ small-angle X-ray scattering

The formation of micro/mesoporous zeolites by treating zeolite crystals with alkaline hydroxides has received a lot of interest, but fundamental understanding is still lacking. Here, we study the reactivity of a crystalline zeolitic material with various alkaline hydroxides, to close this knowledge gap. The use of ex situ and in situ small-angle X-ray scattering has allowed us to determine the reactivity of faujasite (FAU) type zeolite Y at different pH and Si/Al ratio (SAR), with a variety of different organic ammonium hydroxides. Supplemented with ex situ XRD and BET isotherm measurements, we show that the pH of the starting mixture and SAR of the zeolite significantly influence the stability of the microporous structure and the extent of formation of mesoporous material.

Bottom ash from smouldered digestate and coconut coir as an alkalinity supplement for the anaerobic digestion of fruit waste

Anaerobic digestion (AD) of readily hydrolysed substrates such as fruit waste requires the addition of a pH buffering agent. This study evaluated the use of bottom ash from the combustion of spent coconut coir and the digestate produced from rejected berry fruit and plant waste as a buffering agent. The performance of the ash was compared with using an equivalent amount of NaHCO3 as a buffering agent. Digestions of berry fruit waste were performed in 160 mL serum vials using anaerobic wastewater sludge as an inoculum. The methane yield at the optimum levels of buffering with NaHCO3 as the buffering agent was 233 ± 12 NmL CH4/g VS. The methane yield at an equivalent addition of alkalinity as ash was significantly less, (124 ± 3 NmL CH4/g VS), but still beneficial compared to the methane yield obtained from experiments with no added alkalinity (40 ± 1 NmL CH4/g VS). Further dosages of ash in systems containing optimal level of NaHCO3 buffer also revealed a decrease in the methane yield proportionally to the added ash concentration, which is suggested to be caused by soluble concentrations of Fe in the ash supplemented systems that are higher than reported inhibitory levels.

Dissolution of a submarine carbonate platform by a submerged lake of acidic seawater

Abstract. Submarine sinkholes are found on carbonate platforms around the world. They are thought to form and grow when groundwater interactions generate conditions corrosive to carbonate minerals. Because their morphology can restrict mixing and water exchange, the effects of biogeochemical processes can accumulate such that the sinkhole water properties considerably diverge from the surrounding ocean. Studies of sinkhole waters can therefore reveal new insights into marine biogeochemical cycles; thus sinkholes can be considered “natural laboratories” where the response of marine ecosystems to environmental variations can be investigated. We conducted the first measurements in recently discovered sinkholes on Luymes Bank, part of Saba Bank in the Caribbean Netherlands. Our measurements revealed a plume of gas bubbles rising from the seafloor in one of the sinkholes, which contained a constrained body of dense, low-oxygen ([O2] = 60.2 ± 2.6 µmol kg−1), acidic (pHT = 6.24 ± 0.01) seawater that we term the “acid lake”. Here, we investigate the physical and biogeochemical processes that gave rise to and sustain the acid lake, the chemistry of which is dominated by the bubble plume. We determine the provenance and fate of the acid lake's waters, which we deduce must be continuously flowing through. We show that the acid lake is actively dissolving the carbonate platform, so the bubble plume may provide a novel mechanism for submarine sinkhole formation and growth. It is likely that the bubble plume is ephemeral and that other currently non-acidic sinkholes on Luymes Bank have previously experienced acid lake phases. Conditions within the acid lake were too extreme to represent future marine environmental responses to anthropogenic CO2 emissions on human timescales but may reflect the impact of proposed schemes to mitigate climate change by the deliberate addition of CO2 and/or alkalinity to seawater. Other Luymes Bank sinkholes did host conditions analogous to projections for the end of the 21st century and could provide a venue for studies on the impacts of anthropogenic CO2 uptake by the ocean.

The effect of pH, temperature, and inoculum on the fermentation of pulp and paper biosludge: increasing the nutrient availability for rearing of black soldier fly larvae

Pulp and paper production is one of the largest global industries producing annually 400 million metric tons of pulp and paper products and 6 million tons of pulp and paper biosludge (PPBS). From a resource efficiency and sustainability perspective, there is a need for improving PPBS management. This study assessed fermentation of PPBS as pretreatment to improve PPBS feasibility as feed for black soldier fly larvae. The impact of temperature, pH, and inoculum on the concentration of soluble chemical oxygen demand (sCOD) and volatile fatty acids (VFA) was assessed. An initial pH of 10 and the addition of inoculum from an anaerobic digester substantially increased the concentration of sCOD. The obtained concentration of VFA was low compared to the VFA concentration needed to improve the growth of Black Soldier Fly Larvae (BSFL). The PPBS is recalcitrant to fermentation because of the high content of lignocellulose. Fermentation as done in this study does not convert PPBS to a feasible feed for black soldier fly larvae; thus, further research on improved fermentation is needed. However, fermentation at alkaline pH and addition of inoculum do increase the final pH of PPBS which improves its feasibility as feed for BSFL. Future studies should explore pH > 10 and temperatures > 55 °C to increase sCOD and improving generation of VFA by removal of inhibiting substances, testing other types of inoculum (rumen microorganisms) and co-fermentation.

Effects of alkalinity addition with different strategies on CANON process: Start‐up, performance, and microbial community

AbstractThe effects of alkalinity addition with different strategies on the start‐up, performance, and microbial community of completely autotrophic nitrogen removal over nitrite (CANON) were investigated over 450 days. In phase I, the alkalinity was increased gradually from 300 to 2,000 mg/L to obtain the optimal range. In phase II, the reactor was restarted to verify the appropriate alkalinity value of 1,600 mg/L. The fact that it only took 90 days (phase I: 170 days) to complete the start‐up of CANON in phase II demonstrated that an alkalinity value of 1,600 mg/L was suitable when the influent NH4+‐N concentration was 200 mg/L (alkalinity/NH4+‐N = 8:1). The slope (k = 2.00) of NH4+‐N concentration decrease in phase II during the start‐up process was significantly higher than that in phase I (k = 1.50). High removal efficiencies of NH4+‐N (98%) and TN (80%) were attained in both phases. Specific anaerobic ammonium oxidation (anammox) activity tests showed that the anammox activity of the two phases reached 3.31 and 5.31 mg TN/(g VSS·h), respectively. High‐throughput sequencing analysis revealed that appropriate alkalinity could promote the enrichment of Candidatus Brocadia, C. Jettenia, and C. Kuenenia (total abundance of 31.96%) while effectively inhibiting Nitrospira (abundance of less than 0.50%).Practitioner Points An alkalinity/NH4+‐N ratio of 8 promoted the rapid start‐up and stable performance of CANON. NH4+‐N and TN removal efficiencies of 98% and 80%, respectively, were obtained. High alkalinity promoted the enrichment of Candidatus Brocadia, Candidatus Jettenia, Candidatus Kuenenia and inhibited Nitrospira.

Effect of Alkaline Additives over V-Based Catalysts Supported on y- Al2O3 for Propane Oxidative Dehydrogenation

The olefins product are more reactive than the corresponding alkanes, and may easily be super-oxidised into CO and CO2 in selective oxidation of alkanes. The proper balance of acid and base sites on the V-based catalyst surface plays a decisive role in limiting the complete oxidation of alkanes. Therefore, our goal was to evaluate the promoting effect of alkali metals and the support effect using boehmite as precursor for the propane oxidative dehydrogenation (ODH) reaction. Catalysts were prepared via co-impregnation of V and Na or K on a synthesized alumina support. The following characterization techniques were used: N2 adsorption-desorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) and isopropanol decomposition testes to evaluate the acid-base character. The catalyst performance in the propane ODH reaction was evaluated at the O2:C3H8:He molar ratios of 5:2:4, 6:1:4, and 4:3:4. The K-doped catalysts exhibited higher propene selectivity owing to the modification of acid-base character that rendered the weaker interaction between olefinic intermediate and more basic catalyst surface. A high molar fraction of O2 of the reaction mixture minimized coke formation and a high reoxidation rate possibly increased catalytic activity and propene selectivity.

Recovery of phosphate and ammonium nitrogen as struvite from aqueous solutions using a magnesium–air cell system

The addition of alkaline and magnesium sources during the recovery of NH4+ and PO43− in the form of struvite using the traditional struvite precipitation method increases the production cost. To solve this problem, a magnesium–air cell (MAC) system was used herein to recover NH4+ and PO43− as struvite from wastewater using a magnesium strip (Mg2+) and the oxygen adsorbed on the surface of a titanium plate (OH−) as the anode and cathode, respectively. Experimental parameters (i.e. initial solution pH, temperature, NH4+/PO43− molar ratio, NH4+ and PO43− initial concentrations and stirring intensity) were found to affect the removal rate of NH4+ and PO43−. The presence of Ca2+ decreased the struvite purity. At Ca2+/PO43− ratios of 0:1 and 0.5:1, the purity of the obtained struvite after 6 h was 93.8% and 58.9%, respectively. Struvite with a purity of 95.7%, electricity with an average output power of 2.53 mW, and an energy density of 1.05 W/m2 were obtained when the proposed system was used to recover NH4+ and PO43− from an actual supernatant of domestic sludge anaerobic digestion. Scanning electron microscopy–energy-dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy and thermogravimetric analyses showed that the obtained struvite exhibited almost the same physicochemical properties as commercial struvite. Thus, the MAC system can be regarded as an effective method for recovering NH4+ and PO43− in the form of struvite from wastewater.

A novel and efficient N-doping carbon supported cobalt catalyst derived from the fermentation broth solid waste for the hydrogenation of ketones via Meerwein–Ponndorf–Verley reaction

Most of the non-noble metal catalysts used for the Meerwein–Ponndorf–Verley (MPV) reaction of carbonyl compounds rely on the additional alkaline additives during preparation to achieve high efficiency. To solve this problem, in this work, we prepared a novel N-doped carbon supported cobalt catalyst (Co@CN), in which the carriers were derived from the nitrogen-rich organic waste, i.e., oxytetracycline fermentation residue (OFR, obtained from oxytetracycline refining workshop). No additional nitrogen sources were used during preparation. The results showed that inherent nitrogen in OFR could provide N-containing basic sites, and formed Co-N structures via coordinating with cobalt. The Co-N sites together with the coexisting Co(0) cooperated to catalyze the conversion of ethyl levulinate (EL) to γ-valerolactone (GVL) by MPV reaction. Co(0) dominated the activation of H in isopropanol, while Co-N dominated the formation of the six-membered ring transition state.

Hydrothermal Pretreatment of Rice Straw with Alkaline Addition for Enhancing Biogas Production in Semicontinuous Anaerobic Digester

This study presents the results of hydrothermal pretreatment of rice straw on its ability to improve the biogas production process in anaerobic digesters. Hydrothermal treatment on rice straw biomass was carried out with the addition of 0%, 3% and 5% NaOH (w/w rice straw) for one hour at a temperature of 140 °C. This study showed that hydrothermal and alkaline hydrothermal pretreatments were able to increase organic degradation of rice straw as indicated by an increase in the dissolution of lignin and hemicellulose from rice straw. Temperature and NaOH worked synergistically to dissolve lignocellulose in the hydrothermal pretreatment process. In the semicontinuous digester fed with pretreated rice straw, NaOH content in the pretreatment stage was found to give significant effect in enhancing biogas production. Average daily biogas production by the untreated rice straw, hydrothermal pretreated without NaOH addition, hydrothermally treated rice straw with 3% NaOH and 5% NaOH was 23.9, 57.1, 95.8 and 108.8 L/kg rice straw, respectively.

Development and research of the influence of the composition and concentration of activators on the strength of phosphorus slag binders

The paper discusses various ways of activating phosphorus slags by introducing additives for the development of phosphorus slag binders (PSB), replacing cement. Considering that pseudowollastonite is the main mineral of phosphorus slags and without activating components does not possess the binding properties necessary for the production of building materials based on them, we used compositions of small amounts of sodium hydroxide with alkali metal salts, the anions of which form poorly soluble compounds with calcium. When choosing activating components, scarce alkaline additives were replaced by waste from chemical plants, which allows a passing solution of their practical use and environmental problems. The strength at a sodium hydroxide content of 1–4 % after curing of slag samples of various batches was in the range of 50.0–70.0 MPa. Samples of binders of normal hardening at the age of 28 days with a sodium hydroxide content of 0.5; 1.0, 2 and 4 % had the strength of 20.3; 35.4; 45.6; 55.8 MPa, respectively. The effect of the combined presence of alkali and salt is especially noticeable for small amounts of sodium hydroxide. Binders containing a composition of cement with salts under normal conditions and after curing showed a slightly lower strength than in an alkaline medium. With a constant cement content (4 %), the strength indicators increase with an increase in the proportion of the salt additive, reaching at 4 % its maximum value. The effect of the nature of activators on pH was determined. The data obtained indicate the advantages of using PSB and various industrial wastes with a low content of alkaline compounds in the production

Multi-parameter detection of 4 years and coupling analysis of lubricating oil for tugboat engine

ABSTRACT In this paper, through the continuous analysis of the engine oil of a 2600HP tugboat in 4 years, the detection data of spectrum, viscosity, moisture, degree of vulcanisation, pH, fuel dilution, flash point, and oxidation degree are obtained. The variable of these parameters over time is discussed. Nothing abnormal wear is found in the main friction parts of the engine. Lubricating oil is seriously vulcanised and acidification, which affects the oxidation degree. The performance of oxidation, sulphisation, PH, and fuel dilution is seriously degraded. The coupling effects of water content, acid value, alkali value, vulcanisation degree, and mechanical impurity should be considered in determining the oxidation and ageing of lubricating oil. It should be noted that excessive loss of alkaline additives in tugboat operation. The results provide an effective reference basis and experience guidance for better judging the wear state of the friction pair and condition-based maintenance based on lubricating oil.