Concentration Of Solution Research Articles

Optimization of Germination Conditions for Enriched γ-Aminobutyric Acid and Phenolic Compounds of Foxtail Millet Sprouts by Response Surface Methodology.

The optimum germination conditions for foxtail millet sprouts enriched with γ-aminobutyric acid (GABA) and antioxidant polyphenols were investigated. From single-factor experimental results, both the GABA level and total phenolic content (TPC) were more significantly affected by soaking temperature and time, and concentration of sucrose culture solution. Response surface methodology (RSE) was used to optimize the germination conditions of foxtail millet sprouts, where the interaction between soaking temperature and sucrose concentration exhibited a significant (p < 0.05) effect on TPC, and the interaction between soaking time and sucrose concentration displayed a significant (p < 0.05) effect on GABA content. The optimal germination conditions for TPC and GABA enrichment of foxtail millet sprouts were soaking at 31 °C for 4.5 h and germinating at 35 °C with 4.5 g/L sucrose solution for 5 days. Under the optimized conditions, the TPC and GABA content of foxtail millet sprouts were 926.53 milligrams of ferulic acid equivalents per 100 g dry weight (mg FAE/100 g DW) and 259.13 mg/kg, separately, with less difference from the predicted values of 929.44 mg FAE/100 g DW and 263.60 mg/kg, respectively. Collectively, all the individual phenolic compounds increased significantly (p < 0.05) by optimization, except for cis-p-coumaric acid and cis-ferulic acid in bound. The results provide a practical technology for suitable germination conditions to improve the health components of foxtail millet sprouts and increase their added value.

Experimental study and analysis of the static and dynamic mechanical properties of graphene oxide cement soil under composite salinity erosion

In coastal and saline-alkali regions, cement soil materials face significant challenges from salt erosion and both dynamic and static loads, threatening their structural stability. To enhance the mechanical properties of cement soil, this study explores the incorporation of graphene oxide (GO). We subjected GO cement soil specimens to various concentrations of a composite salt solution (with a NaCl to Na2SO4 mass ratio of 1:1) in erosion experiments lasting 7 and 30 days. The specimens were analyzed through unconfined compressive strength tests, split Hopkinson pressure bar (SHPB) tests, and scanning electron microscopy (SEM) to examine changes in stress-strain curves, peak stress, and energy dissipation. The results indicate that the dynamic and static peak stresses, energy absorption, and energy absorption efficiency of the GO cement soil specimens are inversely related to the concentration of the mixed salt solution. Notably, in a 4.5 g/L erosion environment after 7 days, an increasing trend was observed in static peak stress, energy absorption, and energy absorption efficiency. Additionally, when the salt concentration was fixed, these properties showed a positive correlation with impact gas pressure. SEM analysis revealed that the nucleation effect of GO and its strong bonding with the cement matrix significantly improved the microstructure of the specimens by reducing pores and defects, thus enhancing density and overall performance. Furthermore, in an 18 g/L erosion environment, a notable presence of ettringite (AFt) was identified in the GO cement soil specimens.

Cent-Hydro: A Novel Temperature and Pressure-Controlled Hybrid System for Large-Scale Nanofiber Production

The present study aimed to develop a novel temperature and pressure-controlled hybrid system (Cent-Hydro) for large-scale nanofiber production. Nanofibers from a hydrophilic carrier matrix were prepared using the Cent-Hydro system. This study explores the effect of increasing working temperature on the surface tension and viscosity of polymer solutions. The Cent-Hydro system was calibrated through the process of jet formation, and spinning parameters were identified for the jet path. The formation of fingers in front of the thin liquid occurred due to Rayleigh–Taylor instability, and a lower concentration of polymer solution favoured the development of thinner and longer fingers. The critical angular velocity and initial velocity for jet formation were obtained when the balance between surface tension, centrifugal force, and viscous force was achieved. The effect of increasing rotational speed and working temperature on finger velocity and length was experimentally evaluated, concluding that an increase in working temperature increases finger velocity and length. Additionally, the effect of increasing rotational speed, polymer concentration, and working temperature on the diameter of the nanofiber was evaluated. Overall, the Cent-Hydro system presents a compelling proposition for large-scale nanofiber production, offering distinct advantages over conventional methods and paving the way for advancements in various applications.

Experimental Investigation of the Influence of Composition Changes in Shale on Pore Structure and Fractal Characteristics under Different HCl Concentrations.

Acidification is a promising stimulation technique for improving the pore structure of low-permeability shale reservoirs and enhancing shale gas production. Variations in the mineral composition and acid concentration play a significant role in altering the pore systems in shale reservoirs, thereby affecting shale gas transport and production. To investigate the effect of shale composition on pore structure and fractal characteristics under hydrochloric acid (HCl) treatment, experiments were carried out on carbonate-rich (68%), carbonate-medium (45%), and carbonate-poor (2%) shales with different concentrations of HCl solution (1, 5, 10 wt %). X-ray diffraction (XRD), low-temperature nitrogen adsorption, and fractal theory were performed to investigate variations in mineral composition, pore structure, and fractal characteristics of the unreacted and reacted shales. The results illustrated that the HCl treatment significantly reduced the content of carbonate minerals, and the dissolution degree of carbonate minerals increased with the increase in HCl concentration. More meso- and macropores were generated for carbonate-rich and carbonate-medium shale, while more micro- and mesopores were generated in carbonate-poor shale, which led to the increase in total pore volume (TPV) and total specific surface area (TSSA) at different degrees. Moreover, the pore surface roughness (D 1) and structure complexity (D 2) were reduced with the increase of HCl concentration for carbonate-rich shale, while the alteration of D 1 and D 2 showed an opposite trend for carbonate-poor shale. Additionally, D 1 decreased and D 2 increased for carbonate-medium shale. Relevant results could provide theoretical references for the acid fracturing of shale reservoirs with varying mineral compositions.

Theoretical analysis of heat and mass transfer characteristics of a counter-flow packing tower with different heating modes

Mass extraction/injection and multi-stage system have been proven to be effective approaches to improve the performance of humidification and dehumidification (HDH) desalination system. However, these two optimization schemes cause that the flow ratios of water to air at different positions of humidifier or that of different humidifiers have great difference. A single heating mode is inapplicable to all flow ratios of water to air. Hence, it is necessary to reveal the relationship among mass flow ratio, heating mode and thermal efficiency of humidifier for the selection of appropriate heating mode. A theoretical model of packing tower (typical kind of humidifier) which agrees well with experimental results was established in this paper, and the average relative errors of outlet air temperature, humidity and thermal efficiency are 2.3 %, 4.9 % and 5.8 %, respectively. A comparison among the thermal efficiencies of a counter-flow packing tower with different heating modes (I: solution heated, II: air heated, III: solution-air heated) was conducted. It is found that there exist two values of mass flow ratio (FRI-II and FRII-III) at which the thermal efficiencies of air heated and solution-air heated are equal and that of solution heated and solution-air heated are equal, respectively. However, the thermal efficiency of solution heated is always higher than that of solution-air heated (FRI-III does not exist). It seems clear that there is a relationship between FR and thermal efficiency (η) as follows: FR < FRI-II, ηI > ηIII > ηII; FRI-II < FR < FRII-III, ηI > ηII > ηIII; FR > FRI-II, ηII > ηI > ηIII. Additionally, the effects of inlet parameters on the FRI-II and FRII-III are also evaluated. The results show that the maximum temperature, inlet solution concentration and ambient temperature have positive effects on FRI-II and FRII-III, but ambient relative humidity has negative effect. In the final part, the selection of the heating mode of a counter-flow packing tower is taken as example to introduce the application of FRI-II and FRII-III proposed in this paper.

Bottom-up effects of nutrient solutions on grape-grape phylloxera (Daktulosphaira vitifoliae) interaction.

Fertilizers generally influence the nutritional quality or defense ability of the plants, which can indirectly cause an increase in populations of herbivorous insect pests such as grape phylloxera, Daktulosphaira vitifoliae (Homoptera: Phylloxeridae, Fitch). The effects of nutrient solutions on grape-grape phylloxera interactions were analyzed using five concentrations (nitrogen content: 15, 30, 60, 120, and 180mg/L) of Hoagland's nutrient solution to irrigate Vitis vinifera L. × Vitis labrusca L. (Kyoho). Life table variables and life history variables showed a hump-shaped or an inverted hump-shaped curve as nutrient input level increased. Sixty microgram per liter treatment resulted in the greatest longevity and egg incubation, shortened the nymph duration and significantly increased the adult lifespan. Overall, both excessive and insufficient nutrient inputs curbed growth and multiplication of D. vitifoliae. These results provide a theoretical basis for vineyards for amending fertilizer inputs to prioritize the prevention and control of this pest.

Cross-Linked Polyimide Aerogels with Excellent Thermal and Mechanical Properties.

With the increasing development of productivity, new materials that allow for the efficient use of energy are slowly becoming a sought-after goal, as well as a challenge that is currently being faced. For this reason, we have made aerogels as the target of our research and prepared different series (CLPI (1-5)) of cross-linked polyimide aerogels by mixing and cross-linking the heat-insulating cross-linking agent 1,3,5-tris(4-aminobenzylamino)benzene (TAB) with polyamic acid solution. We created a three-dimensional spatial organization by using vacuum freeze-drying and programmed high-temperature drying, then controlled the concentration of the polyamidate solution to investigate the concentration and TAB's influence on aerogel-related properties. Among them, the shrinkage is reduced from 40% in CLPI-1 to 28% in CLPI-5, and it also shows excellent mechanical characteristics, the highest compression strength (CLPI-5) reaches 0.81 MPa and specific modulus reaches 41.95 KN m/Kg. In addition, adding TAB improves the aerogel thermal resistance, T5 in N2 from PI-2 519 °C to CLPI-2 556 °C. The three-dimensional network-type structure of the aerogel shows an excellent thermal insulation effect, where the thermal conductivity can be as low as 24.4 mWm-1 K-1. Compared with some protective materials, cross-linked polyimide aerogel presents better flame-retardant properties, greatly improving the scope of its application in the industrial protection.

Design of a novel ternary blended Self-Compacting Ultra-high-performance Geopolymer Concrete

In this research study, the Taguchi orthogonal array (TOA) optimisation method was used to design the optimum mixture proportions of ternary blended Self-Compacting Ultra-High-Performance Geopolymer Concrete (SCUHPGC). The SCUHPGC mixtures, cured at ambient conditions, included Ground Granulated Blast Furnace Slag (GGBFS), Fly Ash (FA), and Silica Fume (SF) as aluminosilicate sources and sodium hydroxide solution and sodium silicate solution as alkaline activators. The effects of six factors at three levels on the compressive strength of SCUHPGC were investigated. The considered factors were the binder content, the ratio of fly ash to ground granulated blast furnace slag (FA/GGBFS), the ratio of silica fume to binder content (SF/Binder content), the ratio of alkaline activator to binder content (AAL/Binder content), the ratio of sodium silicate to sodium hydroxide (SS/SH), and the concentration of sodium hydroxide solution. Twenty-seven SCUHPGC mixtures were evaluated. The slump flow diameter of the optimum SCHUPGC was 740 mm, which satisfies the requirements of self-compacting concrete. The maximum 28-day compressive strength of 132.7 MPa was achieved by the optimum SCUHPGC mixture, which contained a binder content of 1050 kg/m3, a FA/GGBFS ratio of 0.3, an SF/Binder content ratio of 0.05, an AAL/Binder content ratio of 0.4, a SS/SH ratio of 4.0, and an SH concentration of 12 M. The 28-day flexural strength and tensile strength of the optimum SCUHPGC mixture were 9.6 MPa and 4.9 MPa, respectively.

Ultrasonic-Assisted Extraction and Antioxidant Evaluation of Resveratrol from Peanut Sprouts

The orthogonal array design method was used to optimize ultrasonic-assisted extraction of resveratrol from peanut sprouts. The results showed that the highest extraction yield of resveratrol using ultrasonic-assisted extraction could be up to 1.1%. The optimal extraction conditions were liquid to solid ratio of 30:1 (mL/g) and ethanol concentration of 80% (v/v) as solvent for 40 min at the temperature of 70 °C. AB-8 macroporous adsorption resin was used to purify the crude extract and the resveratrol content increased to 47.5% after one treatment run. The optimal adsorption parameters were initial concentrations in the sample solution of 2 mg/mL, a pH of 5.0, a flow rate of 2 mL/min, and a temperature of 25 °C. The optimal desorption parameters were 60% ethanol and a flow rate of 1 mL/min. The chemical composition of the peanut sprout’s resveratrol sample was investigated via HPLC, and the predominant constituents were found to be protocatechuic acid, catechins, caffeic acid, epicatechuic acid, resveratrol, and rutin. The antioxidant activities of the resveratrol were measured via the following different analytical methods: reducing power, 2,2-diphenyl-1-picrylhdrazyl (DPPH), hydroxyl radical-scavenger activity, superoxide radical-scavenger activity, the β-carotene bleaching test, and the scavenging nitrite test. The results indicated that the resveratrol in peanut sprouts have significant antioxidant activities and can be used as a source of potential antioxidant. And peanut sprout’s resveratrol has the potential and valuable application to be used as a new type of resveratrol resource. The finding of this study can provide some theoretical reference for the comprehensive utilization of peanut resources in the development of antioxidant health foods.

Sulfuric Acid Leaching Recovery of Rare Earth Elements from Wizów’s Phosphogypsum in Poland

Rare earth elements (REEs) are considered vital raw materials for the economy and are on the European Union’s list of critical raw materials (CRMs). Europe is mainly dependent on REE imports. This dependence could be reduced if locally available primary or secondary resources would be processed. In Poland, there are, for instance, over 5 million metric tons of phosphogypsum (PG), a fine powdery byproduct from the fertilizer industry, available near the former Wizów Chemical Plant near Bolesławiec. This material that is considered a waste in Poland contains significant amounts of REEs that could theoretically be recovered and contribute to Europe’s economy. This work is the first systematic analysis of REE leaching studies with sulfuric acid and PG from Wizów. Process parameters such as temperature, particle size, concentration of the leaching solution, and the addition of oxidant and reductant agents were tested to determine the most efficient process. Ultimately, a leaching efficiency of 99% was obtained. Lanthanum exhibited the highest leaching efficiency at almost 100%, followed by Yttrium, Neodymium, Terbium, and Dysprosium. The results of the laboratory experiments are promising and suggest that larger pilot or commercial experiments can be performed next.

Development and evaluation of biocompatible coated microneedle array for controlled insulin delivery: Fabrication, characterization, in vitro, and in vivo investigations

Traditional insulin administration for people with diabetes often involves painful injections, leading to discomfort and challenges with patient compliance. A promising alternative to these conventional methods is transdermal insulin delivery using microneedle arrays, which offer a more comfortable way to deliver insulin through the skin. This study introduces an innovative approach using 3D-printed microneedle arrays coated with insulin via a dip-coating process. These microneedles present a compelling alternative to traditional injections, particularly due to their ability to gently pierce the stratum corneum, the outermost layer of skin, while minimizing discomfort. The microneedle arrays were fabricated using biocompatible resin polymers through 3D printing, creating solid conical needles with a length of 1200 µm, a base diameter of 200 µm, a tip diameter of 80 µm, and a needle spacing of 1.2 mm. The insulin coating was achieved by dip-coating the microneedles in a solution of insulin and polyvinyl alcohol (PVA), with careful optimization of the solution concentration, immersion time, and withdrawal speed to ensure a uniform and controlled coating thickness. Mechanical stability and skin penetration capabilities of the microneedles were assessed using skin models such as parafilm and porcine skin. The tests confirmed that the coated microneedles are robust enough to consistently penetrate the skin. In vivo studies with diabetic rats were conducted to evaluate skin irritation, penetration, and drug delivery efficiency. The insulin-coated microneedle arrays successfully penetrated the skin and delivered the drug with approximately 90 % efficiency. The study also showed that the microneedles provided consistent drug delivery, and the skin recovered without any signs of injury. Additionally, the hypoglycemic effect of the insulin-coated microneedles was comparable to that of traditional subcutaneous insulin injections. These findings underscore the potential of microneedle arrays as a painless and effective method for insulin delivery, maintaining stable glucose levels over an extended period. The demonstrated safety and efficacy of the coated microneedles open the door for clinical trials and potential use in diabetic patients, offering a promising advancement in diabetes management.

Electrochemical sensor for the detection of serine β-lactamase catalytic activity

A new approach is proposed based on the use of electrodes modified with carbon nanomaterials to determine enzymatic activity and screening for inhibitors of serine β-lactamases such as extended spectrum β-lactamases (ESBLs). These enzymes are responsible for the development of antibiotic resistance of pathogenic bacteria to β-lactam antibiotics. Electrochemical oxidation of cephalosporin antibiotic cefotaxime was effectively registered at a potential E from +596 to +625 mV (relative to Ag/AgCl). This property makes it possible to determine the change in cefotaxime concentration in solution upon interaction with serine β-lactamases. By analyzing the electrochemical characteristics of the cefotaxime oxidation reaction, the kinetic parameters of its hydrolysis catalyzed by the serine β-lactamase CTX-M-116 were determined. The Michaelis constant was KM = 50 µM and the maximum rate of the catalytic reaction was 1.67∙10–6 M/min. A comparative analysis of the electrochemical parameters of the enzyme/substrate cefotaxime and enzyme/substrate cefotaxime/inhibitor sulbactam (SBT) systems was carried out. Inhibition of β-lactamase by sulbactam was characterized by an IC50 value of 2.5 μM. The proposed approach can be used for screening new substrates and inhibitors of β-lactamases.

Inhibition sensitivity of invitro firefly bioluminescence quantum yields to Zn2+ and Cd2+ concentrations in aqueous solutions.

To elucidate the inhibition effects of Zn2+ and Cd2+ on the luciferin-luciferase reaction, we performed quantitative measurements of quantum yields and spectral shapes for invitro firefly bioluminescence in aqueous solutions containing ZnSO4, ZnCl2, CdSO4, and CdCl2 at different concentrations. Particular care was taken toward the equilibrium between metal ions and enzyme proteins, anion difference, solubility, and uncertainty evaluation. The bioluminescence quantum yields decreased almost linearly to the concentration of Zn2+ and Cd2+ below 0.25 mM. No obvious difference was found between the chloride and sulfate anion solutions. We defined inhibition sensitivity as the decrease in relative quantum yield versus the concentration of metal ions, and they were determined to be 1.48 ± 0.13 and 1.13 ± 0.16/mM for Zn2+ and Cd2+, respectively. We estimated the detection limit of inhibition effects as the concentration of metal ions that decrease relative quantum yields by 10%, which were 0.07 mM (4 ppm) and 0.09 mM (10 ppm) for Zn2+ and Cd2+, respectively. The shape of the bioluminescence spectra changed sensitively with the increase in Zn2+ concentrations. The bioluminescence peak energy for 0.10-mM Zn2+ was ~2.2 eV, while that for 0.25-mM Zn2+ was ~2.0 eV. The shape of the spectra changed less sensitively with the increase in Cd2+concentrations, and the peak energy was at ~2.2 eV for Cd2+ concentrations of 0.10 and 0.25 mM.

Catalytic Effects of Potassium Concentration on Steam Gasification of Biofuels Blended from Olive Mill Solid Wastes and Pine Sawdust for a Sustainable Energy of Syngas

The effect of potassium impregnation at different concentrations during gasification, under nitrogen/water steam atmosphere, of char produced via pyrolysis of olive mill residues blended or not with pine sawdust was investigated. Three concentrations (0.1 M, 0.5 M, and 1.5 M) of potassium carbonate solution (K2CO3) were selected to impregnate samples. First, four types of pellets were prepared; one using exhausted olive mill solid waste (G) noted (100G) and three using G blended with pine sawdust (S) in different percentages (50%S–50%G (50S50G); 60%S–40%G (60S40G); 80%S–20%G (80S20G)). Investigations showed that when isothermal temperature increases during the gasification conducted with two water steam percentages of 10% and 30%, the reactivity increases with potassium concentration up to 0.5 M, especially for 100G. Still, higher catalyst concentration (1.5 M) showed adverse effects attributable to silicon release and char pore fouling. Moreover, the effect of the steam concentration on the gasification reactivity was significant with the non-impregnated sample 100G. Finally, a kinetic study was carried out to determine the different kinetic parameters corresponding to the Arrhenius law.

Biosensing beyond Debye screening length using epitaxial graphene field-effect transistors on SiC substrate

We demonstrated the antigen detection beyond Debye screening length using antibody-modified epitaxial graphene field-effect transistors (FETs), which have been considered to be impossible because of the Debye screening length. The transfer characteristics of the graphene FETs with a single crystal epitaxial graphene film showed no concentration dependence of buffer solutions. The capacitance measurements in an epitaxial graphene FET also showed no concentration dependence, indicating that the solution-gate capacitance of the epitaxial graphene FET was independent on the Debye screening length. In addition, the minimum capacitance values were also almost independent for the concentration change. Since the Debye screening length depends on the ionic strength of the solution, which is proportional to the buffer solution concentration, the electrical characteristics of solution-gated epitaxial graphene FETs are almost independent on the Debye screening length owing to their small quantum capacitance. The antibody-modified epitaxial graphene FETs indeed detected the antigen, indicating that the epitaxial graphene FETs can detect the target beyond the Debye screening length without any complicated device fabrication processes and other desalted apparatuses.

Prediction of Dynamic Toxicity of Nanoparticles Using Machine Learning.

Predicting the toxicity of nanoparticles plays an important role in biomedical nanotechnologies, in particular in the creation of new drugs. Safety analysis of nanoparticles can identify potentially harmful effects on living organisms and the environment. Advanced machine learning models are used to predict the toxicity of nanoparticles in a nutrient solution. In this article, we performed a comparative analysis of the current state of research in the field of nanoparticle toxicity analysis using machine learning methods; we trained a regression model for predicting the quantitative toxicity of nanoparticles depending on their concentration in the nutrient solution at a fixed point in time with the achieved metrics values of MSE = 2.19 and RMSE = 1.48; we trained a multi-class classification model for predicting the toxicity class of nanoparticles depending on their concentration in the nutrient solution at a fixed point in time with the achieved metrics values of Accuracy = 0.9756, Recall = 0.9623, F1-Score = 0.9640, and Log Loss = 0.1855. As a result of the analysis, we concluded the good predictive ability of the trained models. The optimal dosages for the nanoparticles under study were determined as follows: ZnO = 9.5 × 10-5 mg/mL; Fe3O4 = 0.1 mg/mL; SiO2 = 1 mg/mL. The most significant features of predictive models are the diameter of the nanoparticle and the nanoparticle concentration in the nutrient solution.

Quantifying the Impact of Nitrogen Concentration Variations on Quality Characteristics of Soilless Cultivated Cherry Tomato

Within the domain of macronutrients, nitrogen has garnered significant recognition as a pivotal element due to its profound influence on both the vegetative growth and quality attributes of a crop. An abundance of scientific research has consistently demonstrated that attaining optimal productivity necessitates the meticulous management of soil moisture availability, complemented by the timely provision of nitrogen during critical growth stage intervals. The study aimed to optimize the nitrogen concentration in a hydroponic solution by testing a range of concentrations. The objective was to systematically examine the effects of different nitrogen levels and determine the optimal concentration for the desired outcomes. The assessment was carried out in a meticulously controlled greenhouse environment from October 2019 to April 2021, with the primary objective of systematically investigating the impact on quality characteristics specific to the rosa variety of cherry tomato. To investigate the effects of different nitrogen concentrations, four distinct levels of 4 mM, 6 mM, 8 mM, and 10 mM per litre of nutrient solution were employed. The nitrogen source consisted of a combination of NO3- and NH4+, with a ratio of 40:60, respectively. The nutrient solution with an 8 mM nitrogen concentration exhibited a significantly augmented effect on increasing the equatorial and polar diameter of fruits, average fruit weight, pericarp thickness, as well as the accumulation of total chlorophyll, ascorbic acid, lycopene, β-carotene, and total soluble solids (TSS) content. These findings demonstrate the pronounced and positive influence of the 8 mM nitrogen concentration on the aforementioned quality characteristics.

Study on the adsorption of phosphate by composite biochar of phosphogypsum and rape straw.

Wastewater containing phosphorus is often added by industrial activities, which is bad for the environment. In this study, composite biochar (PG-RS700) was prepared from phosphogypsum (PG) and rape straw (RS) for the treatment of phosphate in wastewater. SEM, FTIR, XRD and XPS characterization results showed that PG and RS were successfully combined. When PG-RS700 was dosed at 1.5g/L and the phosphate solution concentration was 50mg/L and pH = 8, the phosphate removal rate was 100% and the adsorption capacity was three times higher than the corresponding pure PG and RS. The quasi-secondary kinetic model indicated that the adsorption mechanism was chemisorption, and the maximum adsorption capacity for phosphate in the Langmuir isotherm model was 102.25mg/g. Through pot experiment, the phosphorus adsorbed material obviously promoted the growth of plants. PG-RS700 can be used as a powerful adsorbent to treat phosphate in water and return it to soil as phosphate fertilizer.

An integrated approach to sustainable mine wastewater treatment: Magnesium recovery with anion exchange membranes

With recent emphasis on sustainable and efficient mineral valorization, novel approaches to treating mineral wastewater in natural settings bring both environmental and economic value. This paper presents the results of an applied research to develop an integrated approach to sustainable wastewater treatment that includes an ion exchange process to recover copper and cobalt from mine wastewater, followed by the membrane recovery of magnesium. The paper investigates magnesium hydroxide crystallization process employing an anion exchange membrane (AEM) cell. This process involves the penetration of OH- ions from the alkaline solution through the AEM to the feed solution in exchange for Cl- ions and precipitation of Mg(OH)2 as solid particles. The wastewater was sampled from different mine waste sources from the copper mine tailings dam in South Australia, all containing significant amounts of critical metals, including magnesium, copper, and cobalt. The results have demonstrated the potential for sustainable magnesium hydroxide recovery methods. The findings suggest that the most influential process parameters for magnesium hydroxide recovery and purity are magnesium concentration in the feed solution and sodium hydroxide to magnesium ratio in the alkaline solution and feed solution, respectively. It was also established that the overall recovery of cobalt, copper and magnesium in a combination of ion exchange and AEM processes was achieved at a level near 100 %. The purity of magnesium hydroxide precipitate was achieved in the range of 90–96.6 % and depends mainly on the presence of impurities in brine.

Performance and Mechanism of Porous Carbons Derived from Biomass as Adsorbent for Removal of Cr(VI)

To solve the problem of heavy metal hexavalent chromium (Cr(VI)) pollution in water bodies, this study was carried out to prepare nitrogen-doped porous carbon by using bamboo shoots as the raw material and KHCO3 as the activator, which has a good ability to remove Cr(VI) from water bodies. The prepared N-doped carbon materials were characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), elemental analysis, and scanning electron microscopy (SEM). The results showed that the prepared carbon material had hierarchical pore structures and abundant functional groups, which is conducive to the adsorption of Cr(VI). The effects of various factors on the adsorption performance of Cr(VI), such as the carbon materials prepared under different conditions, the pH of the initial solution, the concentration of the initial solution, and the contact time between the carbon and Cr(VI), were explored. The results showed that the bamboo shoot-based nitrogen-doped carbon materials, especially BSNC-800 (prepared at 800 °C with a mass ratio of KHCO3 to bamboo shoot of 4:1), performed well in removing Cr(VI) from a water solution. The maximum adsorption of Cr(VI) by BSNC-800 under equilibrium conditions was 385.8 mg g−1 (conditions: at the pH of 2 with the initial concentration of 400 mg L−1). The adsorption kinetics and isotherms were analyzed, and the adsorption mechanism was discussed. It can be found that the adsorption of Cr(VI) by BSNC-800 fits better with the Langmuir isotherm model and the pseudo-second-order kinetic model. The adsorption mechanism between the Cr(VI)-containing solution and BSNC-800 was controlled by membrane diffusion and chemisorption. The results broaden the ways of utilizing biomass resources as precursors of carbon materials, which is significant and helpful for applying biomass carbon materials as adsorbents for wastewater treatment.