Ion Exchange Equilibrium Research Articles

Rapid removal and catalytic decomposition of nitrate in anion-exchange resin containing gold nanoparticles toward purification of groundwater

We investigated the catalytic reduction of NO3– in various single-metal-introduced anion-exchange resins (AERs) in 1 bar H2 and observed that the reaction proceeded successfully. Among the metals considered in this study, Au was optimal in terms of catalytic activity and ease of catalyst preparation, whereas Ru exhibited the highest activity. The AER with Au (Au@AER) containing the optimal amount of Au (0.3mmol/g) decomposed 0.38mmol/g of NO3– primarily into N2O under optimized reaction conditions (80°C and 5 h). The decomposition amount corresponded to 41 % conversion. The incorporation of Au into the AER increased its ion-exchange capacity from 1.18 (pristine AER) to 1.46mmol/g (Au@AER); in contrast, the ion-exchange equilibrium constant decreased from 1.4 to 0.83 L mol−1 owing to the change in the structure of the anion-exchange sites in the AER. Au@AER was reusable for ion-exchange removal and catalytic decomposition of NO3– up to five times without performance degradation.

Adsorption and ion exchange of toxic metals by Brazilian clays: clay selection and studies of equilibrium, thermodynamics, and binary ion exchange modeling.

In this study, four Brazilian clays (Bofe, Verde-lodo, commercial Fluidgel, and expanded commercial vermiculite) were evaluated for their adsorptive capacity and removal percentage in relation to different toxic metals (Ni2+, Cd2+, Zn2+, and Cu2+). The best results were obtained by expanded vermiculite, with cadmium removal reaching values of 95%. The most promising clay was modified by the sodification process, and the metal cadmium was used to evaluate the ion exchange process. The clays expanded vermiculite (EV) and VNa-sodified vermiculite were evaluated by equilibrium study at 25, 35, and 45 °C. At 25 °C, EV obtained a maximum adsorption capacity of 0.368 mmol/g and sodified vermiculite 0.480 mmol/g, which represents an improvement of 30.4% in modified clay capacity. At 45 °C, the sodified vermiculite reached 0.970 mmol/g adsorption capacity. The Langmuir, Redlich-Peterson Freundlich, and Dubinin-Raduskevich models were adjusted to the results. Langmuir provided the best fit among the models. The thermodynamic quantities (ΔS, ΔH, and ΔG) demonstrated that the process is spontaneous and endothermic and the metal is captured by physisorption and chemisorption in the studied temperature range. For the ion exchange equilibrium, the binary Langmuir and binary Langmuir-Freundlich models were adjusted to the expanded vermiculite and sodified vermiculite isotherms, respectively. Both models were predictive. Thermal analysis indicated good heat resistance even after material modification. The apparent and real densities demonstrated that after each treatment or contamination, the clayey material undergoes contraction in its structure. An improved efficiency of the adsorbent was found after sodification.

Nitrate Uptake from Water Using Amine‐Functionalized Meso‐ and Macroporous Carbons

AbstractMeso‐ and macroporous carbon materials modified with protonated amino groups (−NH3+Cl−) for aqueous nitrate (NO3−) uptake were prepared by surface functionalization with aminopropylsilane. Although the silane coupling treatment decreased the specific surface area of the carbons, surface modification with the −NH3+Cl− group improved the NO3− uptake capacity of both meso‐ and macroporous carbons. The amount of NO3− adsorbed depends on the specific surface area of the adsorbent; an adsorbent with a larger specific surface area exhibits a larger uptake capacity. Enhanced NO3− adsorption onto the NH3+Cl−‐modified surface occurred through an ion‐exchange mechanism. Changes in the pH of the sample solutions before and after NO3− uptake revealed the competitive exchange of NO3− and OH−. NO3− uptake is inhibited by the coexistence of anions other than NO3− (excess Cl−, SO42−, CO32− and HCO3−) and/or OH− at high pH. In particular, the influence of excess Cl− reveals that NO3− uptake through ion exchange is not irreversible, and the adsorption capacity is determined based on the ion exchange equilibrium.

Numerical evaluation of mercury concentration by using a distributional multimedia model in the Lake Biwa-Yodo River Basin, Japan

A distributional multimedia model was developed and applied to the Lake Biwa-Yodo River Basin in Japan to reproduce the mercury level in different environmental media. This model was developed based on a Level III steady-state fugacity model, and the space was divided into four environmental media (atmosphere, water, soil, and sediment). The mass transfer of Hg in this model consists of emission, deposition, sedimentation inside one medium, and advection between different media. The dissolution rate and ion exchange equilibrium have also been considered. We estimated Hg emissions in the Lake Biwa-Yodo River Basin from 1957 to 2009 based on the Pollutant Release and Transfer Registry (PRTR) system and the domestic usage of Hg in Japan. The distribution of emission was based on land data, including industrial land area, industrial location, and proportion of the population. The calculated and observed Hg concentrations were compared to evaluate the model. At both large scale and small scale, results showed that the distributional model could predict Hg concentrations in all environmental media. Sediment and soil media showed the accumulation of Hg by showing the higher concentrations than that of other media. In terms of geographical distribution, the urban area and downstream of the river showed high Hg concentrations owing to high Hg emissions. The Hg concentration in the atmosphere was affected by the transboundary pollution. Thus, the distributional multimedia model could reliably calculate the environmental Hg concentration and be utilized in environmental monitoring and management.

Іntensification of ion exchange processes in water supply systems

In today's environment, special attention is paid to various methods of intensifying natural and wastewater treatment processes, improving existing treatment technologies, and introducing new methods and techniques to improve the quality of wastewater treatment and reduce the anthropogenic impact on the ecosystem. It is important to take into account not only the effectiveness of cleaning, but also its environmental friendliness and compliance with modern standards and requirements for environmental protection. This approach helps to ensure the sustainability of ecosystems and preservation of water resources for future generations. The article highlights the issues related to the use of physical methods of water treatment in water supply systems. To intensify the processes of ion exchange in water supply systems, a method of adjusting the mineral composition of natural and waste water using modified ion exchangers is proposed, which involves the simultaneous action of a magnetic field on the ion exchanger and the water to be treated. The use of magnetic modification of ion exchangers allows to increase the productivity of water treatment facilities by an average of 25-30%, with the receipt of filtrate of the required quality, to increase the duration of the filter cycle, to reduce the consumption of regenerative solutions, which indicates an increase in the efficiency of water treatment as a result of the use of magnetic modification. An increase in the dynamic volume capacity of ion exchangers by 15-20% was found, which indicates an improvement in ion exchange capacity due to the intensification of ion exchange processes in water supply systems. The intensification of ion exchange processes during the adjustment of the mineral composition of natural and wastewater using a magnetic field is determined by the following main factors: the effect of the magnetic field on the structure and properties of water filtered through the ionite and the effect of the magnet field on the activity and mobility of the exchanged ions, their diffusion and hydration, ion-exchange equilibrium, and other factors.

Towards a zero liquid discharge process from brine treatment: Water recovery, nitrate electrochemical elimination and potential valorization of hydrogen and salts

This research addresses the issues related with treatment and valorization of brines and nitrate decontamination of surface and ground waters. The objective was to approximate to zero liquid discharge (ZLD) minimizing the environmental impact of brines of an electrodialysis reversal water treatment plant (EDRWTP) as an example. The innovative in flow process was developed from lab to pre-industrial scale and joined several main concepts: ion-exchange equilibrium for softening or demineralization of brines; reversed osmosis to recover suitable water and to enrich the waste in nitrate for efficient electrochemical reduction of NO3− to N2; valorization of subproducts by direct use or by precipitation; and assessment of the whole process by measuring in-line several parameters. The achieved softening was around 98 % and the recovered water from this current by reversed osmosis was 75 %. The brine of this step (25 %) contained around 1500 mg/L of nitrate and it was treated by electrochemical reduction with a Bi/Sn cathode providing a gas current of 60 % of initial nitrate reduced to N2, O2, H2O, NH3 and at least 97 % of H2. The aqueous current contained around 40 % of initial nitrate as ammonium and nitrite lower than 50 and 5 mg/L, respectively. Hypochlorite was added to this last current for oxidizing ammonium and nitrite to N2 and nitrate, respectively, being nitrate and ammonium lower than 50 and 5 mg/L, respectively. After the obtained water was demineralized and conducted to the EDRWTP inlet. The recovery of insoluble salts as calcium carbonate, reuse of saline solutions for the regeneration of process resins and the potential use of hydrogen generated as a by-product during the electrochemical reduction are other possible utilities.

CsBr-Triggered Reversible Phase Transition of Perovskite Nanocrystals for Advanced Information Encryption and Decryption.

Luminescent perovskite nanocrystals (NCs), possessing the advantages of low cost, easy detection, and excellent luminescence, are becoming more and more significant in the fields of information encryption and decryption. Most hydrochromic perovskite NCs for information encryption have moderate reversibility and are easily passively decrypted by water in the moist air, limiting their practical applications. Herein, a lyochromic material is synthesized based on reversible phase transition between luminescent CsPbBr3-HBr (pretreating CsPbBr3 with HBr) and nonluminescent Cs4PbBr6, exhibiting excellent reversibility in 50 cycles triggered by CsBr solution. HBr treatment boosts the ion migration of NCs via diminishing surface ligands and passivating Br vacancy, assisting CsBr concentration acting as a crucial factor in dynamic ion exchange equilibrium between the trigger solution and CsPbBr3-HBr. By utilizing CsPbBr3-HBr as a safety ink, the CsBr-triggered photoluminescence switch has been demonstrated to be reproducible, stable, and reliable for information encryption and decryption.

Elimination of free fatty acid from palm oil by adsorption process using a strong base anion exchange resin

Deacidification is one of the important processes to obtain a suitable raw feedstock for the production of bio-transformer oil. This work proposed an alternative process for reducing the acidity of refined palm oil by adsorption of the free fatty acids (FFAs) using anion exchange resins (AER). The effect of the types of functional groups (tertiary amine and quaternary ammonium group) and the resin structure (gel and macroporous structure) of the commercially available resins were characterized and investigated for their adsorption ability. The adsorption kinetic and experimental conditions such as adsorption time, the moisture content in resin, and resin amount were studied. The gel-type strong-base anion exchange resins exhibited the best performance for the FFAs removal. This result suggests that the quaternary ammonium functional groups in the resin have a high dissociation capacity for anion exchange and the gel-type resins easily access by the FFAs molecules. The effect of types of functional groups is stronger than that of the resin structure. The adsorption mechanism mainly occurred via an ion exchange equilibrium rather than the hydrogen bond complex. The FFAs adsorption on the resins conformed to the pseudo-second-order kinetic model. Under optimum conditions (room temperature, atmospheric pressure, resin dosage of 0.4 wt%, and 8 h adsorption time), the Pall Tec PTA304 resin reduced the acidity in palm oil from 0.5 to 0.02 mg KOH/g with the adsorption capacity at the equilibrium of 589.5 mg/g, achieving approximately 95 % FFAs removal. The negative values of ΔGads0 and ΔHads0 demonstrated that the FFAs adsorption on the Pall Tec PTA304 resin was a spontaneous and exothermic process. This study provides an insight into the interactions between FFAs and anion exchange resins that is useful for further development of palm based bio-transformer oil.

THE STUDY OF ION-EXCHANGE EQUILIBRIUM OF HEAVY METAL IONS Cо2+ AND Cd2+ ON THE NATURAL AND SYNTHETIC SORBENTS

These article summaries the results of studying the sorption equilibrium of ions close to their concentration in the liquid industrial waste. For experimental research, solutions with concentration of Со2+ and Cd2+ ions in the range of 1·10-3–1·10-4 N have been used. These concentrations match to ion con¬cen¬tration in industrial liquid waste with the ions mentioned. In the experiments, the Na+- modified forms of natural sorbents based on clinoptilolite from the Aydag deposit and on bentonite from the Dash-Salakhli (Azerbaijan) deposit were used. For comparison, among industrial sorbents, we used synthetic cation exchanger KU–2–8 (styrene and divinylbenzene co–poly¬mer), which we modified in H+, Na+-form. The thermodynamic constant of ion-exchange equilibrium for differently charged ions, calculated by the Gorshkov-Tolmachev formula, does not depend on the solution concentration, and to calculate this value, it is not required to determine the activity coefficient. Based on experiments to determine equilibrium concentrations, we can recommend inexpensive and available Na-clinoptilolite and Na-bentonite instead of synthetic industrial KU-2-8 for the sorption extraction of Co2+ and Cd2+ ions from wastewater

Complexation of fluoroquinolones with magnesium ions

Aim. To evaluate strength of magnesium ion complexes with levofloxacin and moxifloxacin.Materials and methods. Complexation of levofloxacin, moxifloxacin, and reference ligands (ethylenediaminetetraacetate (EDTA), sodium citrate, and glycine) with magnesium ions in the range from 0.0 to 1.0 mmol / l was studied. The technique developed by the authors (patent RU 2680519 C1) was used to measure the rate of a model formation reaction of a magnesium phosphate coarse dispersion. Complexing activity of ligands was expressed in relation to EDTA activity and compared with the theoretical ion exchange equilibrium constants. The half maximal effective concentration (C50) calculated by the Michaelis − Menten equation was used to evaluate the dependence of the complexing activity on the dose.Results. A correlation between the activity of EDTA, citrate ions, and glycine and the theoretical equilibrium constants (R = −0.87, p < 0.001) was found. In the range from 0.0 to 0.4 mmol / l, both levofloxacin and moxifloxacin showed a lesser complexing effect than EDTA (p < 0.001), and in the range from 0.6 to 1.0 mmol / l, their complexing effect was comparable (p > 0.050). The activity of fluoroquinolones did not differ at any concentration (p > 0.050), but moxifloxacin C50 (0.13 mmol / l; 95% confidence interval (CI) 0.11–0.15) was significantly lower than that of levofloxacin (0.22 mmol / l; 95% CI 0.19–0.26), (p < 0.001). Within the 0.4–1.0 mmol / l concentration range, the activity of levofloxacin was higher than that of citrate ions and glycine (p < 0.001). Complexing activity of moxifloxacin was higher than that of citrate ions within the range of 0.2–1.0 mmol / l, and in the range of 0.4–1.0 mmol / l, it was higher than that of glycine (p < 0.001).Conclusion. The proposed method showed that the complexing activity of fluoroquinolones was close to that of EDTA and exceeded the activity of citrate ions and glycine. The complexation of fluoroquinolones may be associated with their ability to induce side effects associated with magnesium deficiency.

Numerical reproduction of the seasonal variation in dissolved uranium in Lake Biwa

The seasonal variation in dissolved uranium (DU) concentrations in the epilimnion of Lake Biwa, the largest lake in Japan, was successfully reproduced by geochemical calculations.The DU in Lake Biwa's epilimnion was calculated using an ion-exchange-equilibrium model. The model used the water-DU simple mixing based on monthly observations of water sources (river water, rainwater, evaporation, and groundwater) and thermocline depths from previous studies (Mochizuki et al. (2016)), the adsorbed uranium (AU) on the soil surface based on work by Saito et al. (2021), and the chemical equilibrium of major chemical species such as H, C, and Ca. The total uranium (TU = AU + DU), which determines the peak DU level in summer, and cation-exchange capacity of the soil surface (CECZp), which determines the DU decrease in winter, were optimized by reproducing the DU measurements.The DU value calculated by PHREEQC with the ion-exchange-equilibrium model can be expressed as the sum of three dissolved chemical species (DUeq), which constitute on average 97% of the DU calculated by PHREEQC. DUeq values were decomposed and the contribution of each factor was ranked by comparing their seasonal variabilities. The complexation equilibrium had the greatest variability and was proportional to the reciprocal of the cube of hydrogen ions. This indicates that the seasonal variation in DU is caused mainly by variation in pH.The peak in the DU observations lagged behind the peak in the pH observations by approximately 1 month. However, DUeq did not reproduce this peak delay. Therefore, we assumed that when DU fails to reach the ion-exchange equilibrium concentration and the peak delay occurs, it follows a first-order reaction, and the rate coefficient is determined by the reproducibility of the DU measurements. The DUlim, as the adsorption/desorption rate-limited DU, improved the reproducibility of the DU and the delay after the pH peak. This implies that the delay of the DU peak after the pH peak represents the lag from equilibrium to a first-order rate reaction caused by the soil uranium adsorption/desorption rate.

Simulation of Adsorption Process of l-Tryptophan on Mixed-Mode Resin HD-1 with Combined Physical Adsorption and Ion Exchange.

The mass-transfer process of l-tryptophan (l-Trp) in the hydrophobic interaction/ion-exchange mixed-mode resin HD-1 particles and fixed bed was studied experimentally and theoretically. The adsorption kinetics of l-Trp in single-component and multicomponent adsorption systems was investigated under different pH conditions. The co-adsorption of sodium ions (Na+) and l-Trp anions was found to be negligible. A modified liquid-film linear driving force model considering the physical adsorption of l-Trp zwitterions and anions as well as ion exchange of l-Trp cations was proposed. The dissociation equilibria of l-Trp molecules and functional groups on the resin were introduced in the model. The model could well fit the kinetic adsorption curves of l-Trp at different pH values. The presence of Na+ and the impurity amino acid l-glutamic acid (l-Glu) did not significantly affect the mass-transfer rate of l-Trp. The dynamic adsorption processes of l-Trp under different pH and concentration conditions were studied. A modified transport-dispersive model considering axial diffusion, liquid-film mass transfer, and a combined physical adsorption and ion-exchange equilibrium was established, which could predict the adsorption breakthrough curves of l-Trp well. During the dynamic adsorption process, the pH of mobile phase in the fixed bed changed with changing the l-Trp concentration in the mobile phase. l-Trp was well separated from Na+ and l-Glu with the purity of l-Trp higher than 99%, the recovery rate higher than 95%, and a concentration of 4.69 × 10–3 mol/L. The elution chromatographic peaks of l-Trp, l-Glu, and Na+ and the pH of the outlet solution were predicted satisfactorily.

Integrated Process of Ammonium Ion Adsorption by Natural Dispersed Sorbents

The process of adsorption treatment of effluents from ammonium ions is considered as an integrated two-stage process consisting of the stage of adsorption of contaminants by natural sorbents in the apparatus with a stirrer and the liquid separation stage and solid phases. Mathematical models of ammonium ions adsorption from effluents by natural dispersed sorbents are proposed, based on the assumption that the process is described by Langmuir and Friendlich isotherms. The values of ion exchange equilibrium constants for different types of natural sorbents have been established by identifying experimental data for theoretical dependences. The obtained constants can be used to calculate the average concentration of ammonium ions in the solution and in the grain of the sorbent in the process of integrated adsorption process. Based on the analysis of the research results, the optimum method of the spent sorbent separation was selected - separation of the suspension of purified ammonium-containing effluents - spent sorbent under the action of gravity. Indicators of optimization of complex process of sewage treatment from ammonium ions are offered.

A Comparison Study for The Performance of Polyethersulfone Ultrafiltration Mixed Matrix Membranes in The Removal of Heavy Metal Ions from Aqueous Solutions

Polyethersulfone (PES) ultrafiltration membrane blending NaX zeolite crystals as a hydrophilic additive was examined for zinc (II) and lead ions Pb (II) removal from aqueous solutions. The effect of NaX zeolite content on the permeation flux and removal efficiency was studied. The results showed that adding zeolite to the polymer matrix enhanced the permeation flux. The permeation flux of all the zeolite/PES matrix membranes was higher than the pristine membrane. No significant improvement was observed in the removal of Zn (II) ions using all prepared membranes as the removal percentage did not raise above 29.2%. However, the removal percentage of Pb (II) ions was enhanced to 97% using a membrane containing 0.9%wt. zeolite. Also, it was found that this membrane has a higher ion exchange capacity than the other prepared membranes. Two isotherm models (Langmuir model, and Freundlich model) were employed in the analysis of the ion exchange equilibrium data. The experimental data best fitted the Langmuir model with R2 of 0.889 than the Freundlich model.

Opportunities and challenges of high-pressure ion exchange chromatography for nuclide separation and enrichment

With the rapid development of the nuclear industry, more-stringent requirements are proposed for high-level radioactive waste liquid treatment and the enrichment of isotope products. High-pressure ion exchange chromatography has been widely accepted for the fine separation of elements and nuclides due to its advantages, such as high efficiency, environmental friendliness, ease of operation, and feasibility for large-scale industrial applications. Here, we summarized the evolution of high-pressure ion exchange chromatography and the relevant research progress in ion exchange equilibrium and related separation technology. The prospects for application of high-pressure ion exchange chromatography to rare earth elements, actinide elements and isotope separation were discussed. High-pressure ion exchange chromatography represents a promising strategy for the extraction of rare earth elements and actinide elements from high-level radioactive waste liquid, as well as being an effective method for the automated production of high purity isotope products with great environmental benefits. The separation of radionuclides from radioactive liquid are essential for not only the recovery of valuable radionuclides, but also the purification treatment of radioactive waste water. High-pressure ion exchange chromatography has been widely accepted for the fine separation of elements and nuclides due to its advantages including high efficiency, environmental friendliness, ease of operation, and feasibility for large-scale industrial applications.

Impact of resin loading on ion exchange equilibrium for removal of organic matter and inorganic ions

Ion Exchange (IEX) applications for drinking water can be limited due to high volumes of brine, brine waste and treated water corrosivity. Reusing the resin by operating at reduced regeneration frequency can overcome this. However, assessing changes on the resin loading over reuse cycles is complex because multiple presaturant ions participate in the exchange and existing models only account for the exchange with one presaturant ion. This study developed a theoretical multicomponent model for the determination of IEX equilibria when the resin loading increases due to reuse. The model suggested that both electrostatic interactions and admicelle formation were the separation mechanisms. The model revealed that under reduced regeneration frequencies, brine use and waste generation can be reduced by more than 90%, where the bicarbonate-form resin offered the potential for lower corrosivity. However, changes in resin loading after 5 reuse cycles showed that the risk of corrosion increased. For the tested source water, reusing the bicarbonate-form resin every 5 cycles would achieve the most sustainable option with 41% NOM removal and 79% brine and waste reduction. Under these conditions, almost 100% of exchange capacity is recovered after regeneration

How to Measure the Absorption and Desorption Curves of Superabsorbent Polymers in the Presence of Calcium Ions

The absorption and desorption curve of superabsorbent polymers (SAP), which reflects key information of the maximum absorbency and retention capacity, is crucial for the mix designs of internally cured concretes. In this paper, the effect of amount of Ca2+ on the absorption and desorption curve of SAP is studied. Results show that the proportion between amount of Ca2+ and SAP mass has a notable influence on the absorption and desorption curve of SAP, whether in tap water or mimicked pore solution of cement paste. Considering the important effect of amount of Ca2+, it is suggested that researchers need to determine the relationship between the retention capacity and the ratio of amount of Ca2+ to SAP mass in advance before formal measurement using classic tea bag method or filtration method. Furthermore, from the view of the ion exchange equilibrium between SAP and Ca2+, we discussed the mechanism that amount of Ca2+, concentration of Ca2+, SAP type, alkalinity, etc. have decisive effect on the absorption and desorption curve.

Increasing the efficiency of rare earth metal recovery from technological solutions during processing of apatite raw materials

The issues of complex processing of mineral resources are relevant due to the depletion of available raw materials. So, it is necessary to involve technological waste, generated during the processing of raw materials, to obtain valuable components. In the process flow of apatite concentrate treatment using the sulfuric acid method, a large amount of phosphogypsum is produced with an average content of light rare earth metals (REMs) reaching 0.032-0.45 %. When phosphogypsum is treated with sulfuric acid solutions, a part of REMs is transferred to the sulfate solution, from which it can be extracted by means of ion exchange method. The study focuses on sorption recovery of light REMs (praseodymium, neodymium and samarium) in the form of anionic sulfate complexes of the composition [ln(SO4)2]– on polystyrene anion exchanger AN-31. The experiments were performed under static conditions at a liquid-to-solid ratio of 1:1, pH value of 2, temperature of 298 K and initial REM concentration in the solutions ranging from 0.83 to 226.31 mmol/kg. Thermodynamic description of sorption isotherms was carried out by the method based on linearization of the mass action equation, modified for the ion exchange reaction. As a result of performed calculations, the authors obtained the constants of ion exchange equilibrium for Pr, Nd and Sm, as well as the values of the change in the Gibbs energy for the ion exchange of REM sulfate complexes on the AN-31 anion exchanger and the values of total capacity of the anion exchanger. Calculated separation factors indicated low selectivity of AN-31 anionite exchanger for light REMs; however, the anion exchanger is suitable for effective recovery of a sum of light REMs. Based on the average value of ion exchange equilibrium constant for light REMs, parameters of a sorption unit with a fluidized bed of anion exchanger were estimated.

A COMSOL-PHREEQC Coupled Python Framework for Reactive Transport Modeling in Soil and Groundwater.

The CPqPy framework coupling COMSOL and PHREEQC based on Python was developed. This framework can achieve the simulation of diversified situations including multi-physics coupling and geochemical reactions of soil and groundwater. The multi-physics coupling models are calculated in COMSOL, whereas PHREEQC was applied to calculate the geochemical models through the Phreeqpy library in Python. Feasibility and accuracy of CPqPy were verified and applied to two cases, including a solute transport model considering equilibrium reaction and ion exchange as well as a reactive transport model of a variable saturation soil considering kinetic reaction. The results show a high degree of credibility of CPqPy. The framework has the advantages of strong portability, and it can be further used in conjunction with multiple Python calculation libraries, which greatly extends the application of the reactive transport model.

Synthesis of LTA zeolite beads using alum sludge and silica rich wastes

This study successfully recycled alum sludge with either lithium slag or bottle glass to make high purity zeolite LTA beads. The basic synthesis approach was to fuse the waste material with sodium hydroxide then complete hydrothermal crystallization. Separate fusion of individual wastes promoted zeolite LTA formation compared to combined fusion. Preferred synthesis conditions were: 10 Na2O:Al2O3:2.5 SiO2:300 H2O; hydrothermal temperature = 80 °C; time = 5 h. Zeolite LTA purity was between 80 and 85 wt% from the two waste combinations. Use of pseudoboehmite and carboxymethyl cellulose favoured granulation/extrusion/spheronization of zeolite LTA powder. However, the beading process decreased calcium exchange capacity (CEC) from 99.5 to 37 mg Ca2+/g for alum sludge + lithium slag and from 64.5 to 37 mg Ca2+/g for alum sludge + waste glass. Additionally, when using 20 wt% pseudo-boehmite as a binder the ion-exchange equilibrium time increased from 60 to 300 min. The importance of not only making zeolite powder from waste materials but also to extend studies to shaped forms was evident. It is recommended that future studies should also focus on making extrudates or beads as these are the forms used commercially.