Anionic Resin Research Articles

Developing a food waste biorefinery: Lactic acid extraction using anionic resin and impacts on downstream biogas production

Coupling lactic acid (LA) production with food waste (FW) anaerobic digestion (AD) can facilitate the next generation biorefinery to increase revenue and economic viability of FW AD. For this, LA should be effectively extracted from complex fermentation broths with minimal adverse effects on subsequent AD to maximise economic benefit. This study evaluated LA recovery by adsorption using a polymeric resin (BA765), not previously tested for LA, to explore adsorption capacity and kinetics. Furthermore, biochemical methane potential (BMP) tests were utilised to assess the effect of LA extraction on subsequent AD by measuring biogas production from the solid and liquid extraction residues. Optimal adsorption conditions yielded a maximum capacity of 0.21 gLA·g−1resin from pure solutions at pH 2–4, which was insensitive to temperature. However, real mixed fermentation broth impurities reduced LA uptake by 37%. BMP tests showed that the solid and liquid extraction residues had significant methane potential, with only a 21% reduction in overall methane yield compared to the raw fermentation broth prior to LA extraction. LA production outweighed the loss in methane energy in terms of relative value and indicated a FW biorefinery concept could be commercially attractive and technically feasible.

Macro-Reticular Ion Exchange Resins for Recovery of Direct Dyes from Spent Dyeing and Soaping Liquors.

Dyes are a major class of organic pollutants that are well-known for their harmful impact on aquatic life and humans. Several new strategies for removing colours from industrial and residential effluents have recently emerged, with adsorption being the best option. The current study looked at the recovery of direct dyes from aqueous streams for reuse using macro-reticular ion exchange resins (IERs). The investigation includes dyeing single jersey cotton grey textiles with direct dyes from the Isma dye Company in Kafr El Dawar, Egypt. After centrifuging and separating the supernatant liquid, solutions from thirteen different dyes, produced at an average concentration between the wasted and soaping liquor concentrations, were calculated spectrophotometrically from the first dyeing trials. Kinetic data were well fitted with pseudo-second-order rate kinetics. The amounts of dye retained by the anion exchangers increased with a rise in temperature in the case of Strong Base Resin (SBR) and vice versa for Weak Base Resin (WBR). Batch adsorption experiments with SBR and WBR were conducted for each dye, and both Freundlich and Langmuir isotherms were constructed. It was found that adsorption obeyed both isotherms, that monolayer adsorption took place, and that the dye molecular weight, structure, and solubility, as well as the type of anionic resin used, had varying effects on the extent of absorption. The monolayer sorption capacities Q0 determined from the Langmuir isotherm model for the strongly and weakly basic anion exchangers were found to be 537.6 and 692 mg/g for Direct Yellow RL, respectively. As a result, Yellow RL exhibited the greatest adsorption on both SBR and WBR. Orange GRLL, Blue 3B, and Congo Red, on the other hand, were the poorest colours absorbed by the IERs, whereas Blue RL demonstrated good adsorption by SBR and accelerated adsorption by WBR. Most of the dyes may be recovered and reused in this manner.

Mechanochemical synthesis of bismuth-based anion exchange materials to immobilize arsenic pollution - Prospects for advanced treatment of anion-containing wastewater

Many types of anionic pollutants exit in the aqueous environment including the group containing halogen (F-, I-, IO3-, BrO3-, ClO3−), the group containing heavy metals (VO43−, AsO33−, CrO42−, AsO43−), and eutrophic elements resulting from agricultural, aquacultural, urban and industrial activities (NO3−, PO43−). Except for layered double hydroxide, anionic exchangeable resin, few choices are available to work for the treatment of the anionic pollutants. In this study, a new type of anion exchangeable compound was reported as an alternative. Sulfate-based layered bismuth oxide with the formula of Bi2O(OH)2SO4 as a clear crystalline phase was prepared simply by ball milling Bi oxide and sulfate together. Several analytical methods such as XRD, XPS, FTIR were used to characterize the products after the As (V) adsorption to understand the ions exchange mechanism. The excellent performance to fix arsenate anion reaching over 99.9% of As(V) removal percentage with Bi2O(OH)AsO4 as adsorption product was understood probably due to the synergistic effect of several exchangeable anions inside the prepared sample. This research may open a promising way to effectively remove toxic and harmful anions by the newly prepared anion exchangeable materials.

Isolation and Purification of Mustard Glucosinolates by Macroporous Anion-Exchange Resin: Process Optimization and Kinetics’ Modelling

Glucosinolates (GSL) (β-thioglucoside-N-hydroxy sulfates) are rich-sulfur secondary metabolites raising potential biofumigation interest due to their biological properties. Sinigrin and gluconapin are the main glucosinolates present in brown mustard seeds (Brassica juncea). These glucosinolates are very suitable for the development of phytosanitary products due to their fungicidal, bactericidal and insecticidal effects. In this work, the purification of sinigrin and gluconapin extracted from defatted mustard seeds was studied using macroporous anion exchange resins. A strongly and a weakly anionic resin were first tested according to the nature of their functional group and through their selectivity towards glucosinolates. Anion-exchange resin purification was first studied in static (batch) mode in order to determine the optimal operating conditions; it was then tested in a dynamic (continuous) mode (column) to validate the process. In static mode, the adsorption behavior and characteristics of both resins were compared. The results showed that the strongly basic resin PA312LOH ensures better adsorption of glucosinolates and that the experimental data fit well with the Freundlich isotherm. Moreover, analysis showed that PA312LOH resin was selective for glucosinolates purification towards the proteins. The desorption of glucosinolates was then investigated. Firstly, the operating conditions were optimized by studying the effects of salt concentration and the eluate-resin ratio. This preliminary optimization allowed recovering 72.9% of intact sinigrin and the juice purity was increased from 43.05% to 79.63%. Secondly, dynamic (continuous mode) experiments allowed the recovery of 64.5% of sinigrin and 28% of gluconapin by varying the eluent ionic strength and the flow rate. Resin was finally successfully regenerated using NaOH.

Impacts of chloride-form anion exchange seawater regeneration performance

ABSTRACT Seawater was investigated as an alternative regenerant source to conventional salt-imported brine solutions in an anion exchange process treating surficial Florida coastal groundwater for the removal of sulfate and organics. Bench-scale column testing revealed that filtered Sarasota Bay seawater efficiently regenerated the anion resin media; however, sulfate exchange capacity decreased by 8.42% compared with conventional 10% salt regeneration methods. Addition of 3% sodium chloride increased regeneration efficiency, reduced exchange capacity losses to 2.4% as compared to conventional 10% salt regeneration methods. Regeneration resulted in 2.13 mg/L of bromide leakage; however, addition of 3% sodium chloride to seawater reduced bromide leakage to 1.25 mg/L. A correlation between bromide exchange and the regenerant chloride-to-bromide molar ratio (CBMR) was observed, yielding less bromide exchange at higher CBMRs. Bromide adsorption followed pseudo 2nd order kinetics and chemisorption was the rate controlling step. Increasing the CBMR of the regenerant was found to shift adsorption behaviour, allowing intra-particle diffusion to occur sooner. Bromide equilibrium appeared to follow a logarithmic decay as the CBMR of the regenerant increased. Intra-particle and film diffusion mechanisms were evaluated that indicated the presence of diffusion-based processes and more than one rate controlling step. An empirical function was derived to approximate bromide equilibrium adsorption in relation to a regenerant’s CBMR. Seawater as a regenerant when enhanced with sodium chloride shows promise as an anion exchange regenerant; additionally, classification of a seawater regenerant’s CBMR can provide insight into the kinetic and equilibrium relationships of bromide exchange.

Regeneration of Ion-Exchange Resins and Granular Activated Carbon with the Sonochemical Technique for Enabling Adsorption of Aqueous Per- and Polyfluoroalkyl Substances

Regeneration of adsorbents for reuse is crucial for reducing operating costs and maintaining sustainable systems. Few researchers have studied the regeneration of sorbents without using chemical solvents or appropriate methods. The purpose of this study was to evaluate the feasibility of the sonochemical technique (ST) for the regeneration of granular activated carbon (GAC), a mixed cation and anion resin (DOWEX MB-50), and an anion resin (IRA910) for the removal of per- and polyfluoroalkyl substances (PFAS). The ST was performed at 120 kW, and the power density was 250 W L−1 for 30 min. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to examine physicochemical properties of the spent adsorbents. The removal efficiency of the spent adsorbent regeneration occurred in the following order: DOWEX > GAC > IRA910. As the PFAS-adsorbed adsorbents disappeared in the spectrum, the FTIR results showed the existence of a sulfonic group that is similar to the peaks of virgin sorbents. However, this method affected the morphology of GAC and IRA910 but not DOWEX MB-50. Consequently, the ST is a potential alternative to chemical regeneration for DOWEX MB-50 resins. It is also a potential method for an eco-friendly approach to regenerate PFAS-adsorbed materials.

Synthesis and characterization of poly(styrene-co-divinylbenzene) and nanomagnetite structures

The use of iron oxide nanoparticles for the synthesis of adsorbents materials with application in contaminated water remediation is based on both their magnetic and adsorption properties. Poly(styrene-co-divinylbenzene) - Poly(Sty-co-DVB)microparticles are widely known for this use and the addition of magnetite comes to add magnetic properties, however it should not limit the functionalization processes for formation of cationic and/or anionic resins. Thus, there is a concern about the stability of magnetite in acidic environments, as required by the sulfonation process, for example. Furthermore, the synthesis of composites with magnetic nanoparticles is a challenge due to the strong magnetic dipole interactions between particles resulting from the high specific surface area, making them susceptible to aggregation. As well as oxidation during the synthesis process can compromise the structure of the initial magnetic material. In this sense, the present work validated processes for the synthesis of Poly(Sty-co-DVB)/magnetite microparticles that sought, as a final result, the incorporation of magnetite aiming to preserve its initial structural conformation. Thus, started from original synthesis method aimed at the production of Poly(Sty-co-DVB) microparticles without magnetite, to methods in which magnetite nanoparticles is added through two distinct processes, different regarding the use or not of oleic acid in its preparation.In this method article we show:•Combination of methods to preserve the structure of magnetite in the Poly(Sty-co-DVB)/magnetite composite.•Simple method of adding magnetite to the Poly(Sty-co-DVB)/magnetite composite synthesis process.•Magnetite treatment method with oleic acid in Poly(Sty-co-DVB)/magnetite composite synthesis.The samples were characterized using Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and Mössbauer spectroscopy to evaluate the chemical modifications that were introduced in the original synthesis method.

Thorium ion exchange separation from rare earth elements ore samples following a combined attrition and dissolution procedure

Autogenous grinding (without grinding media) may provide some advantages if satisfactory lixiviation efficiency can be achieved on larger grain sizes. This grinding strategy requires less energy and offers important cost savings and reduction of GHG emissions in the mining industry compared to other commonly used approaches. Two attrition cells (1.2 L, 12 L) were designed to conduct a wet autogenous grinding. The combined grinding and leaching experiments were performed using six Canadian rare earth elements (REEs) ore samples to solubilize the REEs while grinding the ore in a modified attrition mill. Sulfuric, hydrochloric and nitric acids were compared under various operating conditions on three different types of ore samples (carbonatite, sedimentary, peralkaline). The addition of an alkaline step was also investigated. Metals dissolution in the 1.2 L attrition mill with or without NaOH addition (T = 20 °C, solid/liquid ratio = 20%, acid concentration [HNO3] = 7.5 M, time = 1 h) was found effective for the carbonatite ore (solubilization efficiencies of 91–99% Th, 29–32% U, 85–91% LREEs, 84–94% HREEs) and the sedimentary ore (solubilization efficiencies of 89–99% Th, 98–99% U, 22–83% LREEs, 48–99% HREEs). Actinide elements often comprise a significant component in REEs ore samples and are considered impurities. Their presence in primary REE mineral resources is problematic from a regulatory and health physics perspective. To overcome these issues, anionic, cationic and chelating resins were tested to remove Th from the nitric leaching liquor. Best separation results were obtained with the impregnated resin Lewatit VPOC 1026. To the best of our knowledge, this is the first time that Lewatit VPOC 1026 was reported in the literature for Th separation from REEs.

Modifying the resin type of hybrid anion exchange nanotechnology (HAIX-Nano) to improve its regeneration and phosphate recovery efficiency

In order to avoid eutrophication of freshwater systems, regulations all around the world have become increasingly stringent toward the maximum phosphate concentration allowed in wastewater discharges. Traditional phosphate removal methods such as chemical precipitation and enhanced biological phosphorus removal struggle to lower phosphate levels to the new requirements. Hybrid anion exchange nanotechnology (HAIX-Nano) is composed of a selective adsorption material able to remove phosphate down to levels close to zero. Moreover, HAIX-Nano is not affected by intermittent flow and does not produce sludge making it an interesting alternative. The regeneration process of HAIX-Nano typically requires a chemical solution with a high concentration of sodium hydroxide (NaOH) and sodium chloride (NaCl) (2–5% w/w of each). To lower the environmental impact and the operational cost of the technology, this study aims to enhance the HAIX-Nano regeneration efficiency. Therefore, the backbone of HAIX-Nano, which is normally a strong base anionic (SBA) resin, was changed for a weak base anionic (WBA) resin. The resulting material (WBA-2) exhibited a higher adsorption capacity than the traditional version of HAIX-Nano (SBA-1) under the tested conditions, while also showing a much higher regeneration efficiency. For a desorption solution of only 0.4% NaOH and no NaCl, WBA-2 showed an average regeneration efficiency of 78 ± 1% compared to SBA-1 with 24 ± 1%.

Effectiveness of Aerator Ventures, Deposition with Magnets, Filtering, and Ion Exchange in One Unit against Reduction of Iron, Total Dissolved Solid, and Marine Well Water

BACKGROUND: It is known the effectiveness of a venturi aerator, deposition with a sand filter magnet and ion exchange in one unit to reduce Fe content, total dissolved solid (TDS) and saltiness (CL content) in clean water, and the ability of ion exchange to reduce CL content is known. AIM: This study aims to analyze the effectiveness of venturi aerator, magnetic sedimentation, filtration, and ion exchange in one unit against Fe, TDS, and CL well water. METHODS: The method used is a quasi-experimental method using aeration with a venturi system, deposition with magnets, filtration, and ion exchange. The population in this study was all water containing Fe and CL in the Darul Kamal sub-district, Aceh Besar. The sample in this study is part of the population following research needs. RESULTS: The results showed an effect of a venturi aerator, deposition with magnets, filtering sea sand, anion, and cation resins in one unit to decrease Fe content and did not affect decreasing TDS content and Salinity. Moreover, a venturi aerator has an effect, deposition with magnets, filtering sea sand, anion, and cation resins in one unit on the decrease in Fe content, TDS, and salinity at deposition time of 24 h. Venturi aerator’s effect on Fe reduction does not affect TDS and CL of well water. There is an effect of venturi aerator and precipitation with magnets, in one unit on Fe reduction, and does not affect TDS and CL of well water. There is an effect of venturi aerator, precipitation with magnets, filtration in one unit on Fe reduction, no effect on TDS, and CL of well water. CONCLUSION: This tool effectively reduces Fe content and effectively reduces Fe, TDS, and salinity at a 24 h deposition time.

A predictive model of organic acids separation by chromatography with strong anionic resins in sulfate form

Organic acids commonly have quite symmetrical chromatography profiles at low pH (< 1.5) with strong anionic resins, but a significant tailing can be observed with succinic and citric acids. Classical adsorption models, like the Langmuir model, fail to predict this behavior, which can have a major influence on mean retention times and profile shapes, therefore on chromatography performances.A new retention model was developed to better predict organic acid separation with strong anionic resin. This model combines a refined Langmuir adsorption model and an ion-exchange model. Organic acid adsorption is assumed to be due to hydrogen bonding with sulfate and hydrogen sulfate counter-anions on the resin. The adsorption capacity depends mostly on molecular size: up to sixteen formic acid molecules could be adsorbed per counter-anions, meanwhile only two succinic acid or one citric acid molecules could be adsorbed.This adsorption model was then embedded in a generic and accurate modeling approach (continuous column with mass balance equations solved by the conservation element/solution element (CE/SE) method). All parameters of this column model were identified by fitting the simulation to experimental results (equilibrium curves and pulse tests). Then, the column model was validated with original experimental results from a binary mixture pulse test (formic and succinic acids). Results show that simulations are much more predictive for multi-component pulse tests, both in terms of profile shape and retention time, which cannot be captured without considering ion-exchange.

Application of ion exchange resins to reduce hardness and scaling of drinking water: Experimental and modeling

In this research, the performance of strong cationic Purolite C-100 Na+, Ambersep IR252 H+, Amberlite IR120 H+ ion exchange resins and an IRA402 OH- anionic resin have investigated to the reduction of hardness and TDS of drinking water in Bushehr, Iran. Also, to demonstrate the efficiency of these resins, the experimental variables affecting the ion exchange process such as contact time and adsorbent consumption were investigated. The results showed that the maximum adsorption capacity in the best operating condition was 48.01, 45 and 36.01 mg.g-1 for Purolite, Ambersep, and Amberlite resins, respectively. The maximum percentage of total hardness reduction parameters, calcium and magnesium ions reduction at best operating condition was 90.086%, 93.085%, 77.27% for Purolite ion exchange resins, 83.84%, 86.70%, 71.59% for Ambersep ion exchange resins and 69.83, 69.41, 69.32 for Amberlite ion exchange resins, respectively. Also, in the compound stage (the combination of cationic and anionic resins), at the best condition, 3 g/L of cationic resin and 12 g/L of anionic resin had the best efficiency in adjusting pH and reducing TDS. To study the adsorption kinetic process of calcium and magnesium ions by three strong cationic ion exchange resins, three pseudo-first-order, pseudo-second-order, and Morris-Weber models were employed. Among these models, the pseudo-second-order kinetic model had the best agreement with the experimental data. The models of Langmuir, Freundlich, Temkin, and Dobinin-Radskvich were utilized for the equilibrium study of hardened ions adsorption (calcium and magnesium). From the equilibrium study of the absorption process, it was founded that this process involves both chemical and physical absorption and the Langmuir model has the best agreement with the experimental data.

Molten salt oxidation and process analysis of anionic exchange resin in Na2CO3-K2CO3 melt

ABSTRACT The oxidation characteristics of anionic exchange resins (AERs) during molten salt oxidation (MSO) were investigated in carbonate melt. The residue after MSO of AERs were carbon, which was confirmed by the X-ray diffraction (XRD) and Raman spectra. The remaining amount of salt-free residue after MSO was evaluated by destruction and removal efficiency (DRE), which indicates that 2 hours is a suitable oxidation time. The morphologies of the AERs after MSO were observed by scanning electron microscopy (SEM). The oxidation process of AERs in MSO was investigated by thermogravimetric analysis (TG) and Fourier Transform Infrared Spectrometer (FT-IR), which revealed that initial AERs, experienced four reaction stages in MSO: dehydration, thermal decomposition of functional groups, carbonization of styrene-divinylbenzene copolymer (ST-DVB), and gasification of carbon. The TG data proved that the presence of carbonate promotes the carbonization process of ST-DVB in AERs. The reason why salt catalyzes this stage had been proved to be that the carbonate captures the nitrogen-containing exhaust gas generated by the oxidation of the anion resin, and produces nitrate with catalytic oxidation ability, which catalyzes the oxidation of the resins effectively. This means that MSO will be an environmentally friendly and efficient method for catalytic oxidation of AERs.

Optimizing the production of biodiesel from palm olein (Elaeis guineensis Jacq.) using a strong basic anionic resin as a heterogeneous catalyst

In this study, the performance of the Purolite A503S anion exchange resin as a heterogeneous catalyst in the transesterification reaction of palm olein (Elaeis guineensis Jacq.) for ethyl biodiesel production was investigated, and the independent variables were optimized based on the maximum conversion to fatty acid ethyl esters. The response surface methodology (RSM) coupled to a factorial design (2³) with a central composite rotatable design (CCRD) was used for optimization. The effects of temperature, catalyst percentage, palm olein:ethanol molar ratio, and their interactions were evaluated. A reaction time of 10 h was established relating conversion versus time, and the stirring speed was determined by assessing the conversion potential ranging from 250 to 1000 rpm. The reactions were performed in a jacketed reactor coupled to a thermostatic bath. The mixtures of triacylglycerols (TAG), diacylglycerols (DAG), monoacylglycerols (MAG), fatty acid ethyl esters (FAEE), and ethanol were quantified by high-pressure size exclusion chromatography (HPSEC), and glycerol content was determined by stoichiometry. A second-order model was adjusted to explain the experimental data from the 18 factorial design trials. A conversion of approximately 98.10 % in ethyl esters was obtained from the optimised variables using a 17.6 % catalyst, palm olein:ethanol molar ratio of 1:12.85 at 49.4 °C. Despite the long reaction time, the Purolite A503S resin is a potential heterogeneous catalyst in transesterification reactions.

Multi-criteria analysis of detoxification alternatives: Techno-economic and socio-environmental assessment

The transformation of fermentable sugars provided from lignocellulosic wastes into biofuels or bioproducts is a key point at second-generation biorefineries. Spent sulfite liquor is a xylose-rich hydrolysate constituting the main residue of sulfite mills producing dissolving cellulose. Due to the presence of the inhibitors in the spent liquor, the most promising valorization options require detoxification before sugars bioconversion.In this work, a multi criteria analysis was implemented to select techno-economic and socio-environmental feasible detoxification alternatives that can be adapted to a wide variety of fermenting scenarios. Total inhibitors removal, phenolics removal, acetic acid removal, lignosulfonates removal, total sugar losses, fixed capital invested, manufacturing costs, waste toxicity, social acceptance, and employment were chosen as the most relevant criteria. The maximum allowable concentration of undesirable inhibitors cannot be established with a general character, and thereby decision-making tools result in feasible and efficient solutions. From a technical viewpoint best solution was anionic resins with a score of 0.68; the most economical alternative was the overliming with a score of 0.76; finally, from a socio-environmental perspective, overliming reached the highest score of 0.78. In addition, three spent liquor biorefinery models were proposed. Based on the multi-criteria analysis and based on the inhibitor's concentration affecting fermentation yields and productivity, the best detoxification alternatives were (1) anionic resins for polyhydroxyalkanoate production; (2) activated carbon for ethanol biorefinery; (3) overliming for xylitol biorefinery.

Flame retardant and anti-dripping modification of polyamide 6 fabric by guanidine sulfamate with enhanced durability

This study focused on durable flame retardant functionalization of polyamide 6 (PA6) fabric using guanidine sulfamate (GAS). The modified PA6 fabric self-extinguished during vertical burning test (ASTM D6413) without droplet; it had a low damaged length of 8.0 cm and a high LOI of 31.3%, showing good flame retardancy. However, the modified PA6 fabric showed poor washing durability. An anionic thin film on fiber surface was fabricated using condensed tannin resin to improve the washing durability. The electrostatic repulsion action between thin film and GAS contributed to a good washing durability of the modified PA6 fabric, reflected by the self-extinguishing ability after 20 washing cycles. The formation of incombustible violates suggested by thermal stability analysis was beneficial to dilute combustible gases, leading to improved flame retardancy of PA6 through a gas-phase mechanism. This work offers a novel approach of developing durable flame retardant PA6 textile by combining GAS modification and anionic resin coating.

Rapid Extraction Chemistry Using a Single Column for 230Th/U Dating of Quaternary Hydrothermal Sulfides

230Th/U dating can provide high-precision age constraints on Quaternary hydrothermal sulfides. However, low content of U and Th often involves extraction chemistry for the separation and enrichment of U and Th, but these chemical processes are very complex. We developed a simplified procedure consisting of total sample dissolution and single-column extraction chemistry, which can reduce the time and improve the accuracy of the dating. Concentrated HCl-HF followed by HNO3 was added to ensure complete dissolution. A single column filled with 0.4 mL of AG 1-X8 anion resin was used, then 8 M HNO3, 8 M HCl and 0.1 M HNO3 were used to elute most of the matrix metals, Th and U. This process provided more than 95% recoveries for U and Th, and negligible blanks. Meanwhile, Pb and Bi interferences were tested and showed no effect on the U and Th isotope ratio. The 230Th/238U activity of the Geological Survey of Japan geochemical reference material JZn-1 in secular equilibrium was determined and showed a radioactive equilibrium (1.00 ± 0.01, n = 5, all errors 2σ) and an in-house standard QS-1 was consistent to 0.0078 ± 0.0001 (n = 8, ±2σ) with an average age of 705 ± 10 yrs BP (n = 8, ±2σ). The technique greatly shortens the sample preparation time and allows more concise and effective analysis of U-Th isotopes. It is ideally suited for the high-precision 230Th/U dating of Quaternary submarine hydrothermal sulfides and sulfides from other settings.

Molecular sieving of alkyl sulfate anions on strong basic gel-type anion-exchange resins

The effort of today's society towards green, wasteless, and economic production technologies brings new challenges concerning the efficiency of chemical processes. Electromembrane separations are considered as one of the possible candidates in tackling the challenges mentioned above. They offer a competitive alternative to industrially employed standard separation processes regarding cost and control. However, their susceptibility to fouling, especially when the processed solutions are of biological origin, hinders their full application potential. Here, we experimentally determine the group of potential foulants by indirect measurement of the internal characteristic dimensions of a strongly basic anion-exchange resin. Such a resin is used in both ion-exchange beds and heterogeneous ion-exchange membranes. We determine the characteristic dimensions by running a set of electrochemical experiments with a homologous series of alkyl sulfates having a molecular weight in the range between 134 and 288 g/mol. The alkyl sulfates represent potential resin (membrane) foulants. Our results show that the alkyl sulfates can be divided into two groups. While the short alkyl sulfates are exchanged by the studied anion resin particle, the long ones virtually block the resin and hinder any ion exchange or transfer in the electric field. The molecules having dimensions corresponding to the length of the alkyl sulfates of the second group or longer are the potential foulants of the studied and related anion-exchange systems. The alkyl sulfate of the critical length has a distance between sulfur and outermost carbon atoms of around 1.18 nm as predicted from its structure in ChemDraw. We showed that the alkyl sulfates of the first group facilitate water splitting reaction, which indicates the water splitting is the primary mechanism of the observed overlimiting current. The electroconvective motion possibly contributing to the overlimiting current at anion-exchange systems is mostly suppressed.

Research on Transfer Rate of Heavy Metals and Harmful Elements in Traditional Chinese Medicine Extraction and Refining Processes and Product Health Risk Assessment.

Ramulus Mori alkaloids, also known as SangZhi alkaloids (SZ-A), is a natural medicine used for the treatment of type 2 diabetes mellitus in China. SZ-A is extracted from Morus alba L., which grows in the natural environment and may be contaminated by heavy metals and harmful elements. These contaminants can enter SZ-A products during the extraction of M. alba, thereby posing a threat to patient health. Therefore, it is necessary to formulate scientific and reasonable limits to ensure patient safety. For this purpose, in this study, we used the extraction process of SZ-A as the object of investigation and determined the content of five harmful elements: Cd, Pb, As, Hg, and Cu in the herb raw material, SZ-A product, and its intermediates obtained in different extraction steps. Next, the transfer rate of harmful elements in the extraction process was used as an indicator to evaluate the ability of different operations to remove harmful elements. Subsequently, the health risks of heavy metals and harmful elements in SZ-A were assessed. Our results demonstrated that M. alba has little risk of contamination by Hg. The cation and anion resin refining processes are the best effective method to remove Cd, Pb, and Cu from the products. However, As is not easily eliminated during the water extraction. There is as much as 87% of As transferred from the herb raw material to the water-extracted intermediate, while Cd, Pb, and Cu are rarely transferred (6% to 17%) under the same conditions. Overall, the results indicate that the regulatory standard limits for Cd, Pb, As, Hg, and Cu contained in natural medicine Ramulus Mori alkaloids are set to 1, 5, 2, 0.2, and 20μg/g, respectively, which is the most scientific and it can guarantee the safety of patients.

Competitive adsorption of pollutants from anodizing wastewaters to promote water reuse

Anodizing wastewater contains principally phosphate (PO43−) anions according to previous studies, but with the purpose to promote water reuse in this type of industry, a complete characterization of wastewater was made to remove other anions and cations also present in significant concentration. Particularly, the adsorption of sodium (Na+), potassium (K+), fluoride (F−), sulfate (SO42−) and phosphate (PO43−) was studied using different sorbents such as: coconut shell activated carbon, bone char, bituminous coal activated carbon, natural zeolite, silica, anionic and cationic exchange resins, a coated manganese-calcium zeolite, coconut shell activated carbon containing iron and iron hydroxide. All sorbents were characterized using FT-IR spectroscopy, potentiometric titration, nitrogen adsorption isotherms at 77 K, X-ray diffraction and SEM/EDX analysis to study the adsorption mechanism. The adsorption studies were performed in batch systems under constant agitation using both standard solutions of each ion and real anodizing wastewater. Results showed that, in general, the adsorption of all anions and cations is higher when mono-component standard solutions were used, since in the anodizing wastewater all species are competing for the active sites of the adsorbent. Na+ present in anodizing wastewater was efficiently adsorbed on coated manganese-calcium zeolite (20.55 mg/g) and natural zeolite (18.55 mg/g); while K+ was poorly adsorbed on all sorbents (less than 0.20 mg/g). Anions such as F−, SO42− and PO43−, were better adsorbed on the anionic resin (0.17, 45.38 and 2.92 mg/g, respectively), the iron hydroxide (0.14, 7.96 and 2.87 mg/g, respectively) and the bone char (0.34, 8.71 and 0.27 mg/g, respectively). All these results suggest that adsorption is a promising tertiary treatment method to achieve water reuse in the anodizing industry.