Separation Of Salts Research Articles

Effect of pH and Cl- concentration on the electrochemical oxidation of pyridine in low-salinity reverse osmosis concentrate: Kinetics, mechanism, and toxicity assessment

To reduce the pressure of salt separation crystallization and contaminants removal, we systematically investigated the electrochemical oxidation of pyridine (Pyr) in low-salinity reverse osmosis concentrate (ROC) using a Ti/RuO2-IrO2 anode with a high-performance chlorine evolution reaction. We mainly focused on the pH- and Cl- concentration-dependent reaction kinetics, degradation mechanisms, and toxicity assessment. Specifically, the Pyr degradation followed a pseudo-first-order kinetic model. A pH-dependent reaction kinetics study showed that reactive chlorine species (RCS) and ·OH were the dominant species that reacted with Pyr. Furthermore, the degradation efficiency of Pyr reached its maximum value at pH 2, owing to the formation of more RCS. Additionally, Pyr degradation depends on the contribution of RCS in the presence of Cl-. Under low and high Cl- concentrations, the secondary effects were free available chlorine (FAC) and ·OH, respectively. The concentration of trichloromethane (TCM) increased to 9.96 μM first and then decreased to 5.42 μM within 90 min. The variation trend in its concentration is consistent with that of the RCS contribution under different pH and Cl- concentration. The active sites of Pyr were calculated using frontier electron density (FED) and Laplacian bond order (LBO) calculations. The degradation performance and mechanisms of Pyr, wherein ring cleavage on the 6 N atom of Pyr was the main mechanism by electrochemical treatment, were explored through theoretical calculations and gas chromatography-mass spectrometry (GC–MS) analysis. The generation of transformation products (TPs) increased the toxicity of the Pyr water after electrochemical treatment. The overall findings provide new insights into the treatment of ROC, offering significant reference information for improving water utilization and near-zero liquid discharge (near-ZLD) of real wastewater.

Thermally modified polyimide/SiO2 nanofiltration membrane with high permeance and selectivity for efficient dye/salt separation

Selective filtration of dyes and inorganic salts is a challenge for the treatment of textile wastewater containing high salt contents. In this study, selective separation performance of PI/SiO2 nanofiltration (NF) membrane for dye/inorganic salt mixtures was substantially improved through directional modulation of its thermal treatment parameters after phase inversion. After thermal modification, the pore size, porosity and roughness were reduced, and the mechanical strength was improved. The PI/SiO2 membrane under optimized thermally-modified conditions (M6, heat treatment conditions: 50 °C for 8 min) possessed high porosity of 79.95%. Besides, the thermally-modified PI/SiO2 membrane revealed high water permeance of 152.87 L m−2 h−1·bar−1 with efficient rejection performance for a variety of typical dyes. In single dye filtration tests, the thermally-modified PI/SiO2 membrane displayed high rejection (>90%) for Coomassie Brilliant Blue (CBB), Congo Red (CR), Trypan Blue (TB) and Direct Black 38 (DB 38), and exhibited excellent permeance (84.21–133.76 L m−2 h−1·bar−1). In addition, the thermally-modified PI/SiO2 membrane could selectively separate dyes and inorganic salts. The membrane exhibited high dye rejection (>90%) and low inorganic salt rejection (<10%) for the filtration tests of CR + NaCl/Na2SO4 and CBB + NaCl/Na2SO4 mixed solutions (2 g L−1). In particular, the permeances of the thermally-modified PI/SiO2 membrane (89.45–130.21 L m−2 h−1·bar−1) were higher than those of many contemporary NF membranes used for the same type of dye/inorganic salt separation. In conclusion, the present study presents a simple, inexpensive and effective thermal modification means, which shows great promise in the selective filtration of industrial dye wastewater.

Pilot-Scale Selective Electrodialysis for the Separation of Chloride and Sulphate from High-Salinity Wastewater.

The separation of chloride and sulphate is important for the treatment of high salt wastewater, and monovalent selective electrodialysis (MSED) has advantages in terms of energy consumption and pre-treatment costs compared to nanofiltration salt separation. Most of the research on monovalent anion-selective membranes (MASM) is still on a laboratory scale due to the preparation process, cost, and other reasons. In this study, a low-cost, easy-to-operate modification scheme was used to prepare MASM, which was applied to assemble a pilot-scale electrodialysis device to treat reverse osmosis concentrated water with a salt content of 4% to 5%. The results indicate that the optimum operating conditions for the device are: 250 L/h influent flow rate for the concentration and dilute compartments, 350 L/h influent flow rate for the electrode compartment and a constant voltage of 20 V. The separation effect of the pilot electrodialysis plant at optimal operating conditions was: the and transmission rates of 80% and 2.54% respectively, the separation efficiency () of 93.85% and the Energy consumption per unit of NaCl () of 0.344 kWh/kg. The analysis of the variation of the three parameters of selective separation performance during electrodialysis indicates that the separation efficiency () is a suitable parameter for measuring the selective separation performance of the device compared to the monovalent selectivity coefficient ().

Experimental Analysis and Modeling of Closed-Loop Redox Flow Desalination

Redox flow desalination (RFD) is an emerging electrochemical process utilizing a redox couple for salt separation, which enables continuous and energy-efficient brackish water desalination. Several redox couples have been used to desalinate water along with energy production (from sustainable sources such as sunlight) and storage. However, an in-depth analysis of the redox reactions and ion transport that occur simultaneously in different components of an RFD electrochemical cell is still lacking. We carried out a series of experiments, with different cell configurations, to elucidate the contribution of individual components to the cell voltage. A closed-loop RFD mediated by ferri-/ferrocyanide as a model redox couple was designed for this analysis. The cell voltage gradually increased as the diluate concentration decreased from 3 to 0.5 g l−1, attributed to the solution resistance, membrane resistance, Donnan potential, and overpotential of the redox reaction. We experimentally measured voltage drops due to each component, the sum of which was in good agreement with the time-variant cell voltage. A phenomenological model was used to fit the experimental concentration and voltage data, and a good fit was obtained. The combined experimental and modeling analysis reported herein is expected to guide a rational design and operation of RFD processes.

Rapid solute transfer photocatalytic membrane: The combination of host–guest interaction and photocatalyst load

Separation of dyes and salts from textile wastewater is essential for the secondary utilization of resources. Here in, with supramolecular β-cyclodextrin (β-CD) and mussel-inspired polydopamine (pDA) as building blocks, an super-selectiveand highly water permeable photocatalytic membrane with a stable intermediate layer of AgBr-Ag3PO4 photocatalyst was developed by in-situ formation of AgBr-Ag3PO4 photocatalyst via in-situ formation, in which the β-CD with an inherent cavity was used to formed honeycomb microstructures via host–guest interaction with pDA. The optimized photocatalytic membrane, demonstrated a superior-separation performance with a water permeance of 101.3 LMH bar−1, while achieved a high rejection of all tested dyes of up to 99% and high salt transport of from synthetic dyes textile wastewater. Under visible light, the AgBr-Ag3PO4 layer exhibited ∼ 100% degradation of dyes attaching on the membrane surface, endowing the membrane with excellent photocatalytic self-cleaning ability. Combining with material and membrane characterization, the separation performance of the membrane was rationalized, demonstrating the advantages of the host–guest interaction between β-CD and pDA and in-situ photocatalytic functionalization. This study guides the rapid separation of angstrom-sized molecules in the membrane separation process.

A zwitterionic copolymer-interlayered ultrathin nanofilm with ridge-shaped structure for ultrapermeable nanofiltration

Interlayered thin-film composite (TFC) membranes have a great potential for enhancing salt separation in wastewater reclamation, because of the highly permeable and selective properties. However, mechanistic insights regarding the structural features of the surface nanofilms and their corresponding interlayers, which lead to enhanced separation efficiency, remain poorly understood. Herein, we report a zwitterionic copolymer 2-methacryloyloxyethyl phosphorylcholine (MPC) and 2-amino-ethyl methacrylate hydrochloride (AEMA) (P[MPC-co-AEMA]) interlayered TFC membrane that exhibits an ultrahigh water permeance of 20.4 L m−2 h−1 bar−1 (almost three folds higher water permeance than that of the pristine PA membrane), together with a simultaneously enhanced rejection of inorganic salts (96.8% against Na2SO4). Detailed mechanistic investigations revealed that the promoted membrane separation property was mainly explained as the enriched amine monomer diffusion-driven instability induced by the P[MPC-co-AEMA] interlayer. This triggers membrane sealing and inhibits its growth, leading to the formation of an ultrathin PA nanofilm with a thickness of 12 nm, a ridge-shaped surface structure with enhanced specific surface area, and enhanced crosslinking. The fundamental mechanism revealed in this study lays a solid foundation for the engineering of the high-performance TFC membrane, which is appealing for the energy-efficient water remediation industry.

Humic Acid Modified Selective Nanofiltration Membrane for Efficient Separation of PFASs and Mineral Salts

Humic Acid Modified Selective Nanofiltration Membrane for Efficient Separation of PFASs and Mineral Salts

Layer-by-layer assembly of cation exchange membrane for highly efficient monovalent ion selectivity

The development of cation exchange membranes (CEMs) with high monovalent/divalent cation selectivity has great potential for enhanced salt separation for wastewater reclamation, and layer-by-layer (LbL) self-assembly of polyelectrolyte films with high monovalent selectivities among cations has expanded the applications of such membranes. However, the structure–property relationship for constructing multilayered polyelectrolyte films with enhanced separation performance remains poorly understood. This study reports a novel CEM engineered by coating a [polyethyleneimine/polystyrene sulfonate (PEI/PSS)]n alternate electro-deposition multilayer on a polyacrylate substrate membrane. The newly developed CEM exhibited a monovalent selectivity of 4.59 for Li+/Mg2+ with an optimal permeation of 0.16 mmol·cm−2·h−1 for Li+, demonstrating a competitive separation property compared to state-of-the-art permselective membranes. A detailed quantitative investigation provides the underlying insights into the monovalent selectivity for each polyelectrolyte layer. The results indicate negligible interface impedance toward monovalent cations but strengthened repulsion against divalent cations, thereby promoting a quick passage for monovalent cations while imposing temporal retardation on divalent cations during the electrodialysis (ED) process. Therefore, this study elucidates the characteristic reason for the enhanced monovalent ion permselectivity of LbL polyelectrolyte membranes in electro-driven separation processes.

Pilot‐Scale Study on Salt Separation of Industrial High‐Salt Wastewater Based on Nanofiltration

AbstractTo explore the effect of nanofiltration on salt separation in high‐salt wastewater, a pilot plant of nanofiltration combined with a “sand filtration–carbon filtration–ultrafiltration–ozone” pretreatment process is designed. The water used in the pilot‐scale study is the sodium salt wastewater from a battery factory in Tianjin Binhai industrial park. Under the continuous and stable operation of the pilot plant, the key consideration is to investigate the retention rate of monovalent and divalent salt ions in high‐salt wastewater by nanofiltration membranes. The results show that the combined process has a good removal effect on pollutants in wastewater. Among them, the removal rates of conventional pollutants such as turbidity, chemical oxygen demand (COD), and total dissolved solids (TDS) are 97.5, 92.35, and 87.06%, respectively. The retention rate of SO42− is as high as 99.7%, but there is a negative retention phenomenon of Cl−. The main inorganic salts Na2SO4 and NaCl in high‐salt wastewater could be effectively separated. The efficiency of the combined process to remove pollutants and different salts mainly focuses on the nanofiltration part. The pretreatment has a specific removal effect on the turbidity and macromolecular organics of wastewater, reducing the pressure for the subsequent membrane process.

White carbon black wastewater treatment by electrodialysis: Salt separation, silicon sol transporting and wastewater recycling

White carbon black (WCB) as an important silica product has been widely used in many industrial processes. At present, precipitation method is commonly adopted for WCB production, in which a large amount of wastewater containing sodium sulfate and silica is produced. Therefore, it is important and urgent to develop an efficient, low-cost wastewater treatment process, which could extract sodium sulfate from wastewater as value-added byproducts and then recycle this wastewater back to WCB process. In this study, electrodialysis (ED) method, as a proven salt-separation technology, was used to treat WCB wastewater. The existence of silica in the wastewater brings more difficulties for its ED treatment. Firstly, to evaluate ED performance on treating WCB wastewater, the effects of applied voltage, flow rate and initial volume ratio on the overall current efficiency (η), recovery ratio (R), residual rate (γ) and concentration ratio (ω) were investigated. The results show that under the optimized conditions, the highest recovery ratio of Na2SO4 could reach 86.45%, the lowest overall residual rate of SiO2 could go down to 2.69%, and the dilute solution could achieve the reuse standard of waste water. Secondly, the influence of silica on ED performance was investigated. It is found that only about 5.91% of silica in wastewater was transporting from dilute solution to concentrated solution under the optimized conditions. The SEM images of ED membrane indicate that after ED experiments some SiO2 particles adhered to the surface of ion exchange membrane, which would not affect ED normal performance in a short term. These results illustrate that ED is an effective, low energy-cost and reliable process to treat WCB wastewater.

Azine-linked covalent organic framework-modified GO membrane for high-efficiency separation of aqueous dyes and salts in wastewater

Dyes, salts, microorganisms, and other pollutants found in wastewater can be harmful to the environment and are difficult to treat. To address this problem, we designed and prepared a graphene oxide (GO) membrane that was modified with an azine-linked covalent-organic framework via dipping and polymerization. This membrane could efficiently remove dyes with molecular weight from 319.85 to 1355.37 (removal efficiency greater than 90%), inorganic salts (greater than 80%), and microorganisms (nearly 100%). The maximum flux of the composite membrane can reach 47 L m−2 h−1 bar−1. The developed membrane was able to carry out its removal effect by utilizing a combination of sieving and electrostatic interactions, showing promising future application prospects. The removal mechanism of the developed membrane is also briefly discussed.

A novel asymmetric structured nanocomposite PEO-Cloisite based membrane for salt and dye separation

In this study a novel approach was adopted to couple cloisite functionalised with PEO nanoparticles to modify the polyether sulfone (PES) at low pressure nanofiltration membrane for the removal of salts and dyes from waste water. PES/f-(PEO-Cloisite) nanocomposite membranes were fabricated by phase inversion process in presence of DMF as solvent. The functionalised PEO-Cloisite mixture was characterised by SEM-EDX and the membranes were characterised by hydrophilicity and morphology. The highest water flux of 152.77 Lm−2h−1 was observed for 4.5 wt% of PEO-Cloisite in PES membrane. Contact angle values reduced from 74.3° to 60.9° with the increase in the concentration of PEO-Cloisite and confirmed the increase of hydrophilicity. The membrane performance was tested using model saline and dye solutions by low pressure nanofiltration under longer run mode. This study infers that modification of PES membranes using functionalised PEO-Cloisite increase the membrane stability can be used to alleviate the fouling in the treatment of industrial waste water.

Interface synthesis of flexible benzimidazole-linked polymer molecular-sieving membranes with superior antimicrobial activity

Benzimidazole-linked polymers (BILPs) are a type of porous organic frameworks (POFs) that possess high microporosity, exceptional thermal and chemical stabilities. Uniform growth of BILP-101x layer (∼95 nm) directly on the hydrolyzed polyacrylonitrile (HPAN) substrate can be realized within 30 min. The microstructure and separation capability of BILPs membranes were feasibly regulated by the precise control of synthetic parameters. Molecular simulations were performed to reveal the inner structure and molecular transportation behavior of the BILPs membranes. The optimized composite membrane exhibits ultra-high water permeance (∼255 L m −2 h −1 bar −1 ) with extraordinarily high dye/divalent salt selectivity, e.g., Congo red (696.7 Da), Direct red 23 (814 Da) > 99.0%, Na 2 SO 4 < 9%. Furthermore, the resultant membranes evince distinct antimicrobial activity due to the abundant benzimidazole groups in the polymer networks, and the colonies of live Escherichia coli ( E. coli ) bacteria were drastically reduced by 98.4%. Therefore, the resultant BILP membranes which exhibit remarkable permselectivity and superior antimicrobial properties are promising candidate for many applications such as dye desalination and water purification. Facile manufacture of flexible BILP membrane for efficient dye/divalent salt separation with ultrahigh water permeability and superior antimicrobial properties. • Thin and flexible BILP membrane was synthesized on top of PAN substrate. • The microstructure and separation performance of BILP membrane have been explored. • The BILP membrane exhibits ultra-high water permeance and dye/salt selectivity. • Abundant benzimidazole groups endow the membrane superior antimicrobial properties.

Aminated substrate based thin film composite nanofiltration membrane with high separation performance by chemically inhibiting the intrusion of polyamide

In this study, aminated PES substrates were prepared and applied for the investigation on the interfacial polymerization of piperazine (PIP) and 1,3,5-benzenetricarbonyl trichloride (TMC) thereon, with relatively low (PIP: 0.1 wt%, TMC: 0.01 wt%) and high (PIP: 0.5 wt%, TMC: 0.05 wt%) monomer concentration. In low concentration condition, thin, dense, and defect-free selective layers were synthesized on the aminated substrates. In high concentration condition, thin film composite (TFC) membranes with thin selective layers and without the intrusion of polyamide into the substrates were formed. The reactions between the aminated substrate and selective layer were confirmed by XPS analysis on the back surface of the selective layer. The aminated substrates based TFC membrane (TFC-48-H) showed high separation performance, including high water permeability as 20.6 ± 0.1 L/m2 h bar and high Na2SO4 to NaCl selectivity as 86.7, indicating the application potential in divalent to monovalent salts separation process. A conceptual model was proposed to highlight the role of the aminated substrates in the interfacial polymerization process as (1) PIP loaders, (2) PIP diffusion hinders, and (3) polyamide intrusion chemically inhibitors in high monomer concentration condition.

Innate connection between salts on preparation and separation performance of Thin-film Poly (piperazinamide) composite membrane

ABSTRACT The development of thin-film polyamide composite membranes is a revolutionary aspect of the history of membrane science. ‘Wet phase inversion’ and ‘interfacial polymerization’ are two important steps in preparing thin-film polyamide composite (TFC) membranes. Poly (piperazinamide) TFC membranes make a strong pitch for greater regulation of selective passage of mono- and bi-valent salts. The result is a resounding success for the salt separation. In this work, an attempt has been made to study the consequence of salt in gelation bath and interfacial polymerization regarding the behavior of TFC membranes to separate salts from water. The water flux through the polysulfone (Ps) membrane decreases (776.15 LMH to 179.56 LMH) with TDS (salt up to 20000 mg/L. The increase in salt concentration in the aqueous phase (5 to 500 mg/L) of the interfacial reaction influences the salt separation abilities of the TFC membranes. It increases salt separation (Na2SO4 8–9% NaCl 4–6%) by adding 500 mg/L NaCl in piperazine-aqueous solution in different base membranes (Ps-I to Ps-VII). The defluoridation performances of the membranes in accordance with the similar trend as SO4 =. The separation follows the sequence: SO4 = > F− > Cl−. The rejection difference (between Pip-IC and Pip-VIIC) is highest as TDS increases, i.e., TDS: 500 mg/L. The flux reduction is similar (i.e., 30%) as in the case of SO4 = and Cl−.

Two-dimensional nanoporous and lamellar membranes for water purification: Reality or a myth?

• Progress in 2D nanoporous and lamellar membranes is critically reviewed. • Sub-nanoporous membranes can achieve high water permeance and rejection. • Lamellar membranes provide effective rejection of dye molecules at high water flux. • Enhanced ion rejection by lamellar membranes requires 2D material functionalisation. • Research is required on scalability, stability, fouling and pore size engineering. Wastewater contains only ∼ 1% impurities that are required to be separated precisely for water recycling and reuse applications, particularly in water scare regions. Membrane-based separation has been recognised as an environmentally-friendly and energy-efficient process for effective pollutant removal and clean water production. To further improve the selectivity and water flux of membranes, two-dimensional (2D) materials, such as graphene and those exhibiting graphene-like properties, have been intensively studied for nanoporous and lamellar membrane fabrication in the last decade. Herein, we critically review the progress in 2D membranes for water purification and uniquely discuss the performance governing factors and research gaps from the standpoint of environmental and material chemists, which are critical to realize 2D membrane commercialization. The major points of this review are: (1) among the six types of reviewed 2D membranes, graphene, graphene oxide and reduced graphene oxide membrane have been predominantly studied for water treatment. (2) atomically thin nanoporous membranes with a defined pore size can achieve excellent water permeance and selectivity but large-scale fabrication of nanoporous membranes with uniform shape and size of nanopores remains a challenge. (3) salt separation performance of the pressurized lamellar membranes may not be comparable to commercial nanofiltration membranes. (4) functionalization or crosslinking of 2D materials is inevitable to stabilize 2D membrane pore structure and/or improve molecule separation. (5) membranes fabricated using emerging 2D materials such as born nitride and MXene appear to show better stability than graphene oxide membranes. (6) several aspects, particularly membrane stability, long-term performance, and membrane fouling propensity need attention to realize commercial application of 2D membranes in water treatment.

Pyrolysis of sulfuric acid-treated chrome-tanned leather wastes: Kinetics, mechanism and evolved gas analysis

Management and safe disposal of chrome-tanned leather wastes generated in leather industry are of great importance due to their potential health risks and environmental hazards. Herein, an integrated strategy was proposed for disposing of chrome-tanned leather scrap (CTLS). This method involves the separation of chromium salts from CTLS with sulfuric acid for recycling purpose, followed by pyrolysis of the acid-treated CTLS in an inert atmosphere. SEM/EDX analysis was employed to characterize the changes in composition and morphology of CTLS after acid treatment. CO2 and H2O are main pyrolysis gases of CTLS, while the acid treatment increases the relative content of aliphatic hydrocarbons and NH3 in evolved gases. The pyrolysis characteristics and kinetics of the acid-treated CTLS were investigated by thermogravimetric analysis (TGA) at three different heating rates. After 3 and 6 days of acid treatment, the average activation energy of CTLS (450.9 kJ/mol) obtained from the Flynn-Wall-Ozawa method decreased to 369.6 and 351.0 kJ/mol, respectively. It is assumed that the CTLS consists of two pseudocomponents: low-crosslinked collagen (LCol) and highly-crosslinked collagen (HCol). Using the generalized master plots method, random nucleation and nuclei growth model (An model) was found to be the most probable kinetic model for the pyrolysis process of LCol and HCol. The kinetic exponent for pseudocomponent pyrolysis varied between 3.00 and 3.90, and the pre-exponential factor ranged from 5.83 × 1012 to 2.93 × 1013 min−1. The results of the present study provide an alternative route and useful information for recycling and disposing of chrome-containing leather wastes.

Efficiency Evaluation of Cavitation Heat Generator Used for Desalination of Saline Solutions

Nowadays, the issue of efficient desalination and treatment of seawater for its further use in various domains of human activity is of much interest worldwide. There are plenty of known treatment techniques. This research paper discusses the method of hydrodynamic cavitation treatment in a heat generator in various modes and proves the performance efficiency of this method. The process of treating saline solutions of different concentrations and registration of electric conductivity of solutions are studied. The possibility of changing the concentration of salt in the solution by treating it in a vortex cavitation heat generator is undertaken. The efficiency of the cavitation process depends on the temperature of the working environment: with the temperature increase, the desalination intensity decreases. Two possible scenarios of the process are revealed, i.e., the decrease in the concentration of salt in the solution or its increase in the presence of a salt source. When working on depleted solutions with a salinity of 1÷5 ‰ at high temperatures, the reverse diffusion of previously adsorbed salts from the internal surfaces into the solution takes place. When working on solutions of elevated concentrations in the same high-temperature range, the reverse diffusion decreases and at a salinity of 67 ‰, its effect ceases, since the concentration of salts on the inner surfaces becomes comparable to the concentration of the solution. The hypothesis of centrifugal separation of salts from water is experimentally proved.

Host-guest nanofiltration membranes having amino-complexed cucurbituril supramolecular channel for monovalent/divalent salts separation

Nanofiltration (NF) is widely used in separation of ions with different sizes and charges. However, thin-film composite NF membrane is hard to reach satisfied selectivity for monovalent/divalent salts separation. Herein, a novel host-guest NF membrane was designed and fabricated with cucurbituril-polyethyleneimine (CB-PEI) complex, which provided a “ring-like” supramolecular channel. The results indicated that CB-PEI/PSf membrane showed attractive separation performance for monovalent/divalent salts separation, purification and desalination of small molecule solutions. The as-prepared CB-PEI/PSf membrane exhibited superior pure water permeability up to 25.6 L·m−2·h−1·bar−1, and salt rejections of 97.4%, 90.6%, 41.9% and 12.4% to MgSO4, Na2SO4, MgCl2 and NaCl, respectively. The monovalent/divalent selectivelies for NaCl/MgSO4 and NaCl/Na2SO4 reached up to 30.0 and 8.9, respectively. Besides, the CB-PEI/PSf membrane exhibited very high separation factors for medicine/NaCl and dye/NaCl mixtures. Moreover, NF membrane processes were designed and operated for monovalent/divalent mixed salt separation by using CB-PEI/PSf membrane. The NaCl with mass fraction above 98% was successfully recovered after the single-stage membrane separation of NaCl/MgSO4 mixture and the two-stage membrane separation of NaCl/Na2SO4 mixture. Therefore, this novel host-guest NF membranes and process design provide a valuable basis for the industrial application of monovalent/divalent salts separation.

Influence of various shapes of alumina nanoparticle in integrated polysulfone membrane for separation of lignin from woody biomass and salt rejection

Lignin valorization is essential in proposing an economic perspective as a raw material for valuable compounds. The bio-refineries require adequate processing to improve the high purity of lignin. Meanwhile, nanofiltration is fascinated attention to obtain high purity value-added products. The effect of alumina nanoparticles on the fabrication of mixed matrix membranes (MMM) has contributed to improvising filtration performance. However, incorporating nanoparticles is a significant issue regarding appropriate size and shape integrated into membrane for better filtration efficiency. The influence of shapes of alumina nanoparticles has been investigated into polysulfone (PSf) membranes for salt and lignin separation. The morphology of alumina was tailored with spindle, cubic, and spherical shapes synthesized at a different calcination temperature of 250, 500, 700 and 900 °C, respectively. The phase transitions were confirmed in X-ray diffraction (XRD) analysis, and the shape of the nanoparticles was observed in a high–resolution transmission electron microscope (HRTEM). The separation efficiency of membranes was tested with salt rejection using sodium sulfate, calcium chloride, potassium sulfate, and sodium chloride. The lignin was extracted from prehydrolysed sawdust, and the synthetic lignosulfonic acid sodium salt solution was separated. The higher lignin rejection of 98.6% and 97.9% were obtained for cubic shaped gamma phase alumina mixed matrix membrane. The high rejection of lignin occurred due to narrow pores channels that could resist the transfer of lignin through the membrane. The results proved that the controllable organization of PSf/alumina mixed matrix membranes could apply for lignocellulose compounds with good efficiency.