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The present study manufactured and utilized the chitosan-coated fumed silica composite (CS@silica) for simultaneous adsorption of rare earth elements (REEs) of Ce(III), La(III), and Nd(III) cations in an aqueous solution. The CS@silica composite underwent characterization using a CHNOS analyzer, Brunauer-Emmett-Teller (BET) surface area analyzer, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrophotometer, scanning electron microscope coupled with energy-dispersive X-ray (SEM-EDX) spectrophotometer, and X-ray diffraction (XRD) analyzer. The findings indicated that the CS@silica composite exhibited a lack of pores and possessed a specific surface area of 1.27 m2/g. Additionally, it was observed that the composite contained a significant amount of oxygen and nitrogen atoms, which serve as the active sites for the adsorption of REEs. The maximum adsorption capacities of Ce(III), La(III), and Nd(III) cations were determined under optimal experimental conditions. These parameters included a pH of 4, an adsorbent dose of 0.01 g, and an equilibrium duration of 20 min. The maximum adsorption capacities for Ce(III), La(III), and Nd(III) cations were found to be 341, 241, and 299 mg/g, respectively. The adsorption kinetics followed the pseudo-second-order kinetic model. The desorption percentage of REEs-loaded CS@silica composite was significantly low when exposed to deionized water and hydrochloric acid (0.01 and 0.02 M). This suggests that there is a chemical interaction between the REEs and the active site on the surface of the composite. The predominant adsorption process proposed was complexation, with ion exchange and electrostatic contact playing a minor role. The CS@silica composite is highly promising for the recovery of REEs because of its rapid adsorption and high adsorption capacities. [ABSTRACT FROM AUTHOR]

Phenol is nonetheless considered a major pollutant and, therefore should be treated to eliminate the phenol in wastewater to save the environment, people, and organisms from the negative impacts of phenol. This study, for the first time, investigates the synthesis and performance evaluation of hexadecyltrimethylammonium bromide-functionalized cellulose nanocrystals (HDTMA-Br/CNCs) adsorbent for removing phenol from synthetic phenol-containing wastewater. The CNCs were prepared from as-received cellulose, by mixed acid hydrolysis consisting of sulfuric acid, glacial acetic acid, and deionized water in a mass ratio of 1:7:2. The prepared CNCs were functionalized by adding 20 g of the produced CNCs to the HDTMA-Br solution and stirred for 120 min. The synthesized and HDTMA-Br-functionalized CNCs were characterized using different analytical techniques, such as Scanning Electron Microscopy (SEM-EDX) to examine the surface morphology and the elemental composition of the modified and unmodified adsorbents. Fourier Transform Infrared (FTIR) was used to examine the attachment of the functional group. X-ray diffraction (XRD) was used to analyze the crystalline structure of the adsorbent. To evaluate the performance of the synthesized adsorbent in batch mode, 1 g/L of phenol was used to prepare the synthetic phenol-containing wastewater. The analysis of the feed and permeate was done using pre-calibrated High-Performance Liquid Chromatography (HPLC). The multi-BET surface area of CNCs was 24.11 m2 g−1, meanwhile, fCNCs possessed a higher surface area of 201.4 m2 g−1 with a pore volume of 0.069 cm3 g−1. About ∼75 ± 1.4% phenol removal was obtained for the functionalized CNCs compared to the non-functionalized CNCs adsorbent having ∼43 ± 0.1% phenol removal at 35 °C reaction temperature. It could be observed that the spent adsorbent a shows percentage phenol removal of 70.0 ± 0.8% and 35.5 ± 1.4%, for fCNCs and CNCs at the 3rd cycle. The Langmuir and Freundlich isotherms best match the experimental data, while the pseudo-first-order kinetic model provided the greatest fit to the kinetic data. Thus far, the results suggest that modified CNCs may be an alternative adsorption material for phenol removal in wastewater. [ABSTRACT FROM AUTHOR]

Concern for environmental protection has increased throughout the years from a global perspective. To date, the predominance of adsorption as treatment technique in environmental chemistry remains unchallenged. Moreover, the scientific attention for investigating nanobubbles due to their unique properties has turned the search for their application in environmental processes with special emphasis on water treatment. This study is aimed at investigating the effect of rotation on batch adsorption process using commercial activated carbon as adsorbent material, compared with the widely used method of agitation. As liquid medium, deionized water and deionized water enhanced with nanobubbles (of air) were used. The wastewater was simulated by dissolving a common dye as model pollutant, methylene blue, at concentration of 300 mg/L in the tested liquid. The results indicated that the utilization of nanobubbles resulted in an improvement on adsorption rate, compared to the corresponding values of deionized water solutions. These results may lead to promising applications in the future, since just 1 h of operation increases the water purification and thus provides a simply applied, cost-effective, and rapid alternative. [ABSTRACT FROM AUTHOR]

The complete removal of low concentration organic pollutants from wastewater to obtain clean water has always been a highly desired but challenging issue. In response to this, we proposed a new strategy to fabricate a carbon-in-silicate nanohybrid composite by recycling dye-loaded layered clay adsorbent and converting them to new heterogeneous carbon-in-silicate nanocomposite through an associated calcination-hydrothermal activation process. It has been confirmed that most of the dye molecules were present in waste rectorite adsorbent using an intercalation mode, which can be in situ converted to carbon in the confined interlayer spacing of rectorite. The further hydrothermal activation process may further improve the pore structure and increase surface active sites. As expected, the optimal composite shows extremely high removal rates of 99.6% and 99.5% for Methylene blue (MB) and Basic Red 14 (BR) at low concentrations (25 mg/L), respectively. In addition, the composite adsorbent also shows high removal capacity for single-component and two-component dyes in deionized water and actual water (i.e., Yellow River water, Yangtze River water, and seawater) with a removal rate higher than 99%. The adsorbent has good reusability, and the adsorption efficiency is still above 93% after five regeneration cycles. The waste clay adsorbent-derived composite adsorbent can be used as an inexpensive material for the decontamination of dyed wastewater. [ABSTRACT FROM AUTHOR]

The current study evaluated the use of pumice, a volcanic mineral and common sand, in treating reverse osmosis membrane reject water (ROR) using a novel combined adsorption distillation (CAD) method. The CAD method is developed to separate the dissolved solids through adsorption distillation, i.e., leaving the vaporized distillate as freshwater and concentrated brine. The adsorption potential of pumice and sand was investigated at different adsorbent doses, i.e., 2, 5, and 10 g, and consecutive CAD adsorbent backwashing cycles. The improved results were achieved at a 10 g pumice dose. However, its adsorption efficiency declined in longer CAD cycles, i.e., due to the separated deposition of solids. After backwashing, the adsorbed and accumulated salts were slightly removed, and pumice adsorption capacity was maintained for up to 20 cycles of CAD. The properties of the pumice, i.e., before and after five CAD cycles and after backwashing, were characterized with scanning electron microscopic (SEM), elemental disruptive spectroscopy (EDS), and X-ray diffraction (XRD), which revealed that the porous structure of the pumice was completely accumulated with deposits of ionic salts, which were slightly washed away after backwashing, but accumulation remained continued in post-CAD cycles. The explored method revealed a high potential of pumice in water filtration. [ABSTRACT FROM AUTHOR]

The present study investigates the removal of glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos herbicides from their 5 × 10–5 M aqueous solutions onto activated carbon cloth by adsorption and electrosorption. Analysis of these highly polar herbicides was achieved by UV–visible absorbance measurements, after derivatization with 9-fluorenylmethyloxycarbonyl chloride. The limit of quantification values of glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos were 1.06 × 10–6 mol L−1, 1.38 × 10–6 mol L−1, 1.32 × 10–6 mol L−1 and 1.08 × 10–6 mol L−1, respectively. Glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos were removed from their aqueous solutions with higher efficiencies by means of electrosorption (78.2%, 94.9%, 82.3% and 97%, respectively) than of open-circuit adsorption (42.5%, 22%, 6.9% and 81.8%, respectively). Experimental kinetic data were fitted to pseudo-first order and pseudo-second order kinetic models. It was determined that pseudo-second order kinetic model represents experimental data better with satisfactory coefficient of determination, r2 (> 0.985) and normalized percent deviation, P (< 5.15) values. Adsorption isotherm data were treated according to Freundlich and Langmuir isotherm models. Based on the r2 (> 0.98) and P (< 5.9) values, it was found that experimental data well fitted to Freundlich isotherm model. Adsorption capacities of activated carbon cloth for glyphosate, glufosinate, aminomethylphosphonic acid and bialaphos, expressed in terms of Freundlich constant, were calculated as 20.31, 118.73, 239.33 and 30.68 mmol g−1, respectively. The results show that the studied ACC can be used in home/business water treatment systems as an adsorbent due to its high adsorption capacity. [ABSTRACT FROM AUTHOR]

In this study, the novel pH‐sensitive s‐IPN consist of sodium alginate integrated with poly(HEMA‐co‐MA) hydrogel matrix are prepared by using two‐step methodology. In the first step, 2‐hydroxyethyl methacrylate (HEMA)/maleic acid (MA) copolymeric hydrogels are prepared by gamma radiation polymerization. Then, poly(HEMA‐co‐MA) hydrogel was immersed in sodium alginate solution (SA) and finally gamma radiation polymerization was carried out. The swelling, pH‐sensivity and diffusion properties of the prepared s‐IPN gels in deionized water and in dye solutions were investigated. Methylene Blue (MB) was used as a model dye. MB adsorption capacities of the hydrogels were found to be 0.26, 0.40 and 13.77 mg MB/g dry gel in PHEMA, P(HEMA‐co‐MA) and s‐IPN SA/P(HEMA‐co‐MA) hydrogels, respectively. MB release data was fitted to various kinetic models to study the dye release behavior. The MB release from all the prepared hydrogels fitted the Korsmeyer‐Peppas model. Swelling, diffusion and MB adsorption properties of the new s‐IPN hydrogel were improved with the inclusion of SA and MA in the gel structure. [ABSTRACT FROM AUTHOR]

Methylene blue dye can cause damage to the eyes of humans and animals, as well as skin irritation. Also, it can result in nausea, cancer, vomiting, convulsions, and diarrhea. Consequently, in this work, an aqueous solution of sodium metasilicate pentahydrate (12 g dissolved in 50 mL of deionized water) reacted separately with two aqueous solutions of magnesium nitrate hexahydrate (8.47 g dissolved in 50 mL of deionized water and 11.47 g dissolved in 50 mL of deionized water) to obtain sodium magnesium silicate hydrate/sodium magnesium silicate hydroxide as novel nanostructures via the sol–gel method. Besides, the synthesized nanostructures were utilized for the efficient removal of methylene blue dye from aqueous media. The mean crystallite sizes of the nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, are 73.17 and 60.25 nm, respectively. The nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, were composed of cubes, spheres, and irregular shapes with mean grain sizes of 175 and 110 nm, respectively. The BET surface areas of the nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, are 171.04 and 189.90 m2/g, respectively. The maximum adsorption capacities of the nanostructures, which were synthesized using 8.47 and 11.47 g of magnesium nitrate hexahydrate, toward methylene blue dye are 384.62 and 404.86 mg/g, respectively. The adsorption of methylene blue dye using the synthesized nanostructures is consistent with the pseudo-second-order kinetic model and the Langmuir equilibrium isotherm. Also, the adsorption of the methylene blue dye is chemical and exothermic. [ABSTRACT FROM AUTHOR]

Two sodium alginate-based Pb2+-imprinted thermosensitive hydrogels (SPIT (without ɛ-PL) and SPPIT (with ɛ-PL)) were synthesized, with sodium alginate and ɛ-polylysine (ɛ-PL) as the matrix, N-isopropylacrylamide as the monomer. Characterization with differential scanning calorimeter, Fourier transform infrared spectroscopy, thermogravimetric analyzer, scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy confirmed the aimed structure of the hydrogels. The adsorption capacity of SPIT and SPPIT for Pb2+ was 98.64 mg/g and 153.49 mg/g, respectively. Washing the Pb2+-loaded adsorbent with 10 °C deionized water, SPIT and SPPIT achieved a desorption efficiency of 94.59 % and 97.51 %, respectively. After 10 cycles of adsorption-desorption process, the adsorption capacity and desorption efficiency remained at about 80–88 % of the original ones, expressing excellent reusability. In a mixture containing eight metal ions (Pb2+, Cu2+, Mg2+, Ca2+, Cd2+, Na+, K+, Fe3+), the adsorption capacity of SPIT to Pb2+ was 92.49 mg/g, and that of SPPIT was 102.49 mg/g, much higher than that to the other ions (1.50–11.38 mg/g on SPIT, 9.48–27.45 mg/g on SPPIT), showing excellent adsorption selectivity. The introduction of ɛ-PL enhanced the adsorption capacity, antibacterial ability and stability of the hydrogel, ensuring better application potential in real wastewater. • Two Pb2+-imprinted adsorbents were prepared with sodium alginate as the matrix. • The differential scanning calorimeter test confirmed the reversible thermosensitivity of the adsorbents. • Washing with cold water (5-10 °C) could regenerate the Pb2+-loaded adsorbents. • After 10 cycles of reuse, 80–88 % of the adsorption capacity was remained. • The adsorptive selectivity coefficient of adsorbent was up to 33.99. [ABSTRACT FROM AUTHOR]

The adsorption process of deionized water droplets on the parallel flow interface between ionic liquid [BMIM][PF6] and mineral oil is investigated in U-shaped microchannels. Three flow patterns of the efficient adsorption, moderate adsorption, and inefficient adsorption based on the adsorption efficiency were observed. The dimensionless droplet length D / W > 0.72 is conducive to efficient adsorption of droplets. When droplet shape factor β > 1, the lubrication pressure generated within the curved liquid film has a more significant hindrance on the adsorption process, and the reverse lubrication pressure at the outlet of the liquid film is the main reason for the rupture of the liquid film. An increase in the velocity of phase interface A-B movement can lead to an increase in lubrication pressure. A correlation model is established between the dimensionless adsorption length L * and the dimensionless adsorption time t *, and the influence of Laplace pressure is analyzed. [Display omitted] [ABSTRACT FROM AUTHOR]

The facile synthesis approach for the adsorbent preparation and recyclability during decontamination of radioactive pollutants is a significant concern in water treatment. The objective of this study is to, synthesis via solid-state reaction of the nanostructured CaTiO 3 for the removal and recovery of strontium (Sr2+) from the various water sources. The influence of the adsorption-dependent parameters including, initial concentration, adsorbent dose, pH, contact time and co-existing ions interference were investigated. The prepared adsorbent was characterized by different analytical techniques like FT-IR, SEM with EDAX, TEM, TGA-DTG, Powder XRD and BET surface analysis. The kinetic models were also used, and according to the kinetic models, a pseudo-second-order kinetic model (R2 = 0.999) was better fitted to the adsorption of Sr2+ ions onto CaTiO 3 rather than pseudo-first-order kinetics, which could properly represent the observed adsorption of Sr2+. For the isotherm study, the results are best fitted to the Langmuir isotherm model (R2 = 0.98) with a maximum adsorption capacity of 102.04 mg/g. The common ions (Na+, Mg2+, Ca2+, and K+) and Sr2+ having a concentration of 1:2, 1:3, and 1:4, where 82.8, 79.5, and 68.2 % removal was achieved of Sr2+ in each respective matrix. In addition, the adsorption and corresponding recovery and removal for the different Sr2+spiked matrices in deionized water, tap water, well water, lake water, and seawater were investigated with 97, 65.6, 76.5, 73.9 and 17.8 % removal respectively. Also, the CaTiO 3 showed excellent recyclability with minimal loss even after 5 consecutive recyclability cycles and >90% removal of strontium achieved. Hence, prepared nanostructured CaTiO 3 could be considered a promising adsorbent for the removal and recovery of Sr2+ions from contaminated water bodies. [Display omitted] • CaTiO 3 nanostructured adsorbent was synthesized through single step synthesis. • Pseudo-second order kinetic model was best fitted to the adsorption of Sr2+. • Maximum adsorption capacity was found 102.04 mg/g. • Sr2+ spiked different water bodies were tested and found 76.5 to 17.8 % removal. • CaTiO 3 showed excellent five successive recyclability cycles. [ABSTRACT FROM AUTHOR]

2,4,6-trinitrophenol (TNP) has various industrial applications and is also extremely used by militaries and terrorists to make various explosives. Owing to their extensive industrial and military use and higher water solubility, their huge quantity is released into the environment and thus become a momentous environmental pollutant. TNP is highly toxic, poorly biodegradable, and a vigorous poison, strongly carcinogenic, and could cause severe diseases in humans and other animals. Thus, TNP present in the industrial wastewater and landfill leachate must be removed due to its detrimental effects on natural ecosystems. In the present review, the nature of TNP and its decontamination approaches are discussed, as well as their detailed mechanisms. The challenges that arise while applying TNP decontamination approaches were discussed and some future directions are highlighted for enhancing the efficiency of these approaches in a sustainable and friendly manner. [Display omitted] • Trinitrophenol (TNP) is a highly explosive and toxic pollutant, causing severe threats to human health and the environment. • Biodegradation, adsorption, photocatalytic degradation, and electrocatalytic degradation were employed to decontaminate TNP. • Incomplete biodegradation and secondary pollution generation in adsorption are the major challenges. • Photodegradation is a suitable treatment for complete remediation compared to conventional treatments. • Mechanistic understanding of the photodegradation of TNP via experimental and theoretical studies needs further exploration. [ABSTRACT FROM AUTHOR]

The aim of this study is the use of a new conducting composite material which was prepared from an agricultural byproduct "olive pomace (OP)" and a polymer "polyaniline doped with a chlorhydric acid (PANI-HCl) and used for the fabrication of electrode, which was then used as substrate for the recovery of chromium hexavalent to an aqueous solution through chemical adsorption and electrosorption tests. We used the spectral analysis techniques such as FT-IR to characterize the material as well as scanning electron microscopy (SEM) to show that the PANI was successfully attached to OP. We carried out adsorption in batch system and electrosorption tests in acid medium within an electrochemical cell at a potential of +800 mV imposed and we compared the recovery with chemical adsorption at open circuit under the same conditions. For batch adsorption tests of Cr (VI) on olive pomace, PANI-HCl and the composites material prepared; the effect of several parameters such as the contact time, and the pH of the solution were studied. For the électrosorption tests, the results demonstrated that the electrosorption capacity of Cr (VI) is superior to the adsorption, which is due to the excellent electrical conductivity and mechanical properties of OP/PANI composite electrode. [ABSTRACT FROM AUTHOR]

As is well known, hydrotalcite-like compounds, such as layered-double-hydroxide (LDH) materials, have shown great potential applications in many fields owing to their unique characteristics, including a higher anion exchange capacity, a structure memory effect, low costs, and remarkable recyclability. While the lower surface area and leaching of metal ions from LDH composites reduce the process efficiency of the catalyst, combining LDH materials with other materials can improve the surface properties of the composites and enhance the catalytic performance. Among organic compounds, carbon materials can be used as synergistic materials to overcome the defects of LDHs and provide better performance for environmental functional materials, including adsorption materials, electrode materials, photocatalytic materials, and separation materials. Therefore, this article comprehensively reviews recent works on the preparation and application of layered double-hydroxide-based carbon (LDH–C) composites as synergistic materials in the field of environmental remediation. In addition, their corresponding mechanisms are discussed in depth. Finally, some perspectives are proposed for further research directions on exploring efficient and low-cost clay composite materials. [ABSTRACT FROM AUTHOR]

The efficiency of saturated Activated Carbon (AC) electrochemical regeneration was evaluated. Reactor configurations in cathodic/anodic process, applied current effect on the properties of AC and Methylene Blue MB-AC interactions and adsorption/desorption mechanisms were studied. The efficiency was measured by adsorption capacity adsorption/regeneration cycles and changes in the adsorbent characteristic were analyzed through FTIR, BET, Optical Microscopy (OM) and SEM before and after the regeneration. The energy consumption was analyzed to assess the economic feasibility. It was found that the electrochemical treatment was efficient in returning the AC adsorption capacity, maximum efficiencies of approximately 79% and 84% were reached when the Carbon Fiber Cloth-AC electrode was subjected to anodic and cathodic currents, respectively, at a current of 0.1 A. In addition, the material demonstrated good stability through adsorption-regeneration cycles by cathodic process, with the material's adsorption capacity being almost totally recovered for 8 consecutive cycles. The removal percentage around 80% was kept after the cycles, with optimal conditions when the electrode was subjected to cathodic currents, NaCI as electrolyte at a current of 0.1 A for 2 h. The characterization techniques provided results that allow to explain the higher and prolonged efficiency of the cathodic current. Furthermore, these reactor configurations achieved an electrical energy consumption of 2.3 and 2.1 kWh kg-1 of material for cathodic and anodic, respectively. These results indicate that the electrochemical is an economical and environmental suitable technique capable of restore carbon adsorbents to be reusable for several water treatment cycles. [ABSTRACT FROM AUTHOR]

Various magnetic carbon materials have been employed for nuclide adsorption, yet there exists a research gap concerning their application in electro-adsorption for nuclide removal. In this study, a magnetic carbon nanotube nanocomposite (Fe 3 O 4 /CNT) was successfully synthesized as an electrode material through the hydrothermal method, involving the modification of minute Fe 3 O 4 nanoparticles onto the surface of carbon nanotubes (CNT). Electrochemical assessments revealed that the Fe 3 O 4 /CNT nanocomposite exhibited a higher specific capacitance compared to Fe 3 O 4 and CNT individually. The HRTEM image reveals a heterojunction structure formed directly between Fe 3 O 4 and CNT, which facilitates electron transmission. The Fe 3 O 4 /CNT nanocomposite was utilized as an electrode in a capacitive deionization (CDI) device for U (VI)-contaminated wastewater purification. Experimental results demonstrated that the maximum U (VI) adsorption capacity of the Fe 3 O 4 /CNT electrode reached 287.53 mg/g at 298 K, and the adsorption process conformed to the Langmuir isotherm model. Kinetic analysis further indicated that the adsorption of U (VI) by Fe 3 O 4 /CNT followed a pseudo-second-order kinetic model. Additionally, the Fe 3 O 4 /CNT nanocomposite was transformed into a flowable electrode liquid and applied in a flow-electrode capacitive deionization (FCDI) system for U (VI) removal from aqueous solutions. Leveraging its superparamagnetic properties, the Fe 3 O 4 /CNT flow-electrode within the FCDI system could be rapidly recovered via a straightforward magnetic separation procedure. Notably, after nine consecutive runs of the FCDI device, the Fe 3 O 4 /CNT flow-electrode successfully concentrated a low-concentration U (VI) solution of 120 mg/L into a high-concentration solution of 1230 mg/L, thereby achieving the goal of water resource conservation and reduced storage requirements. [Display omitted] • The high-performance Fe 3 O 4 /CNT nanocomposite was prepared through a one-pot method. • The Fe 3 O 4 /CNT has a higher specific capacitance because of the synergistic effect. • The Fe 3 O 4 /CNT can be used as an electrode for CDI and FCDI devices to remove U (VI). • The Fe 3 O 4 /CNT flow-electrode can be quickly recovered by magnetic separation. [ABSTRACT FROM AUTHOR]

• The continuous adsorptive removal of phenol using low-cost activated carbon was studied. • Effects of electromagnetic field (EMF), and electric potential (EP) in the phenol removal were studied. • EMF enhanced the removal performance of activated carbon electrodes on the aluminum substrate. In this study, we introduce an electrode configuration setup to study the effect of an electromagnetic field (EMF) and electric potential (EP) on phenol removal in a continuous adsorption process. Feed water contaminated with dissolved phenol was exposed to EMF and passed through charged activated carbon electrodes prepared from Phoenix dactylifera (palm tree) biowaste. This study investigated the effects of magnetic field exposure, electric potential, feed salinity, and electrode substrate type. The results revealed that the highest adsorption uptake capacity of 47.2 mg/g was achieved using an aluminum substrate (AS) with EMF at zero salinity. The phenol adsorption kinetics followed a pseudo-second-order adsorption rate and diffusion model, indicating that intraparticle diffusion was the primary rate-limiting mechanism. The increased phenol adsorption uptake capacity brought on by the EMF may result from the improved mass transfer and mobility of the adsorbate and, consequently, the increased effectiveness of the internal diffusion of the pollutants. Finally, a regeneration efficiency of 99 % was achieved using NaOH at a salinity of 5,000 ppm. [ABSTRACT FROM AUTHOR]

Environmental pollution requires advanced methods and materials to clean drinking water. In particular, 2D transition metal carbides, named MXenes, display unique properties such as specific surface area, surface functional groups, conductivity, and antibacterial effects. Here, we review the applications of MXenes for water purification, and the factors controlling the efficiency of MXenes. We present the history of MXenes and focus on applications for adsorption, capacitive deionization, membranes, and catalysis. [ABSTRACT FROM AUTHOR]

The heavy metals pollutants resulting from industrial wastewater are a major environmental problem due to their toxicity and non-biodegradability. Their removal became a trending environmental subject. The preparation of low-cost and eco-friendly adsorbents for industrial wastewater treatment has been widely investigated. Furthermore, the use of polymeric material for this purpose is highly increasing. In this study, banana stem agro-waste was valorized by preparing and characterizing its derived activated carbon used as a filler to improve the adsorption performance of polyurethane foams. The loaded polyurethane was synthesized in the shape of pellets, characterized by SEM, and tested in removing Pb2+ and Cu2+ from aqueous solutions. The effects of AC filler concentration, number of filtering passes, and pH were examined. The loaded polyurethane demonstrated a good adsorption capacity that was enormously improved compared to the unloaded polymer. 77 % Pb2+ and 40 % Cu2+ removal were reached after one filtering pass only. The optimum pH was determined to be 4. After the 10th pass, and at any pH, almost 100% of the studied metals were eliminated. Rapid and straightforward selectivity and seawater deionization tests were carried out and confirmed the capacity performance of the prepared pellets in removing different aqueous ions. [ABSTRACT FROM AUTHOR]

Powdery hierarchical porous carbons serve as cost‐effective, functional materials in various fields, namely energy storage, heterogeneous catalysis, electrochemistry, and water/wastewater treatment. Such powdered activated carbons (PAC) limit new module designs and require further preparation steps, for example, adding polymeric binders, to be shaped into a standalone geometry. Polymeric binders, however, can block PACs' catalytic and active sites and, more importantly, pose the risk of secondary pollution for environmental purposes, especially in the context of clean water supply. This study introduces a novel synthesis method for fabricating freestanding nitrogen‐doped carbons with hierarchical porosity using chitosan and sucrose as green precursors. Chitosan supplies nitrogen and acts as a backbone, giving a freestanding geometry to the final product, and sucrose is a carbon‐rich precursor. The proposed method employs ice‐ and hard‐templating for macropores and mesopores and combines carbonization and activation steps with no required activating agent. Final freestanding carbons function as adsorbents for removing persistent pollutants, as binder‐free electrodes with high specific surface area and capacitive current, and as tubular gas diffusion electrodes for oxygen reduction reactions. These freestanding carbons enable new module designs and can be scaled‐up by numbering‐up, serving as bio‐based functional materials for a wide range of applications involving porous heteroatom‐doped carbons. [ABSTRACT FROM AUTHOR]

Gas sensors have been widely used in detection of industrial gas leak, air quality detection, and medical diagnosis. Although some chemical sensors have been commercialized, there are still some challenges such as sensitivity, cycle stability, and high power consumption. Metal–organic frameworks (MOFs) have high specific surface area, rich porosity, and excellent reversible/selective adsorption ability for various gases. Therefore, MOFs has been considered as an ideal sensing material. Metal active sites and active functional groups on the surface of MOFs can combine with gas molecules through hydrogen bonds, van der Waals interactions, and electrostatic interactions, resulting in highly effective selectivity and superior cycle reversibility. Meanwhile, MOFs‐based capacitive gas sensor can respond at room temperature, which can largely reduce energy consumption during the test. Therefore, the application of MOFs materials in capacitive gas sensors can effectively solve the above problems. In this review, the latest studies on MOFs‐based capacitive gas sensors for acidic/alkaline, VOCs, and water are summarized, and research prospects based on the mechanism of MOFs as sensing layers and filtering layers are proposed. [ABSTRACT FROM AUTHOR]

In this study, the application of superabsorbent resin (SAP) in inhibiting the soil moisture evaporation (or slowing down the water outflow) was studied. The clay‐SAP composites were fabricated by grafting of poly (acrylic acid‐N‐hydroxymethyl acrylamide/clay) (GT‐g‐P [AA‐co‐NHA]/clay) on Tragacanth gum (GT), using solution polymerization. The structure, morphology and stability of the clay‐SAP composites were investigated by Fourier transform infrared, scanning electron microscope and TGA. The maximum swelling ratio of Attapulgite (3%)‐, Kaolin (3%)‐ and Montmorillonite (3%)‐SAP composite in deionized water reached 1180, 819 and 525 g/g respectively, and the maximum swelling ratio in tap water reached up to 206, 192 and 170 g/g respectively. Meanwhile, the maximum swelling ratio in 0.9% NaCl solution was 95, 82 and 62 g/g respectively. The water retention of clay‐SAP composites was also analyzed as a function of temperature. In addition, by simulating the desertification area, the effect of the APT (3%)‐SAP composite on the anti‐evaporation performance was studied. The obtained results revealed that the water retention of APT (3%)‐SAP composite was 36% at 45°C for 12 h. Under natural conditions, the evaporation rate of the anti‐evaporation material was inversely proportional to the amount of APT (3%)‐SAP composite added. [ABSTRACT FROM AUTHOR]

Featured Application: This work will allow the development of an efficient, cost-effective and sustainable solution to be used in the removal of pharmaceutical products from wastewaters. It also will contribute to better theoretical and practical knowledge of the three-dimensional electrochemical process as a solution for wastewater treatment. The scientific community is increasingly concerned about the presence of pharmaceuticals in the aquatic environment, which is a consequence of their high consumption and inefficient removal by wastewater-treatment plants. The search for an effective and sustainable tertiary treatment is therefore needed to enhance their removal. For this purpose, the combination of electrochemical and adsorption processes into three-dimensional (3D) electrochemical systems has been proposed. In this study, a 3D system was studied to remove carbamazepine, an antiepileptic, consumed in high doses and very persistent in the environment. The influences of the following parameters on its removal were evaluated: anode and cathode materials and distance between them, electrolyte (NaCl) concentration and pH, and the (carbon-based) adsorbent material used as the particulate electrode. The obtained results demonstrated that the introduction of the particulate electrode improved the removal efficiency. This can be attributed to the simultaneous occurrence of different phenomena, such as adsorption/electrosorption, electrocoagulation, oxidation, and catalytic degradation. [ABSTRACT FROM AUTHOR]

A facile, feasible, and green synthesis via an electrochemical exfoliation process was applied to synthesize nitrogen-doped MgO/graphene nanocomposite (N-MgO/G). The N-MgO/G nanocomposite was characterized by several analytical techniques including X-ray photoelectron spectroscopy, X-ray powder diffraction, transmission electron microscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, selected area electron diffraction, and elemental mapping analysis. N-MgO/G nanocomposite was then applied to adsorb lead metal ions (Pb2+) from aqueous solutions. The N-MgO/G nanocomposite demonstrated a remarkably high Langmuir maximum adsorption capacity (294.12 mg/g) for Pb2+ ions under the optimum experimental conditions at a pH of 5.13, time of 35 min, dose of 0.025 g, the concentration of 400 mg/L, and a temperature of 36 °C. Adsorption kinetics results fitted with a pseudo-second-order model and a thermodynamic study showed that Pb2+ adsorption is an endothermic process. The practical application of N-MgO/G was also investigated to test its applicability in real water samples collected from different sources such as deionized water, tap water, wastewater, and river water. [ABSTRACT FROM AUTHOR]

Dairy industrial wastewater is characterized by high chemical oxygen demand (COD) and other pollution loads. In this study, simulated dairy wastewater (SDW) was treated for turbidity and COD elimination via electrocoagulation (EC) with aluminum electrodes. COD concentration was not completely abated and exceeded allowable Algerian direct discharge limits. To enhance rate parameter pollution removal, electrocoagulation (EC) was combined with adsorption (AD) under the same operational electrocoagulation conditions. A full factorial design was employed to determine the optimum operating conditions for dairy wastewater treatment by electrocoagulation used separately or coupled with granular activated carbon (GAC). Current density, initial pH, and GAC mass were chosen as the controlling process parameters and examined at three levels. The results showed that EC reduced turbidity and COD from SDW to 98.75% and 78.09%, respectively, when pH = 4 and with current densities of 20.83-27.77 mA/cm². The EC/AD process enhanced turbidity reduction to 99.39% and COD removal to 87.12% when small masses of GAC (0.5 to 1.5 g) were used at the lowest applied current density level of 13.38 mA/cm². In comparison to classical electrocoagulation using aluminum electrodes in a batch system, coupling electrocoagulation to adsorption technique achieved faster removal of pollutants with lower operating costs. Operating costs of the EC/AD process for turbidity and COD removals were calculated as 0.360 €/m3 and 0.746 €/m³ vs. 0.494 €/m³ and 0.692 €/m³ for the EC process. Correlations with the experimental data for the EC process were R² = 95.78% for turbidity and R² = 96.22% for COD removal. For the coupled EC/AD they were R² = 96.61% for turbidity and R² = 95.48% for COD removal. [ABSTRACT FROM AUTHOR]

Electrochemically mediated selective adsorption is an emerging electrosorption technique that utilizes Faradaically enhanced redox active electrodes, which can adsorb ions not only electrostatically, but also electrochemically. The superb selectivity (>100) of this technique enables selective removal of toxic or high-value target ions under low energy consumption. Here, we develop a general theoretical framework to describe the competitive electrosorption phenomena involving multiple ions and surface-bound redox species. The model couples diffusion, convection and electromigration with competitive surface adsorption reaction kinetics, consistently derived from non-equilibrium thermodynamics. To optimize the selective removal of the target ions, design criteria were derived analytically from physically relevant dimensionless groups and time scales, where the propagation of the target anion's concentration front is the limiting step. Detailed computational studies are reported for three case studies that cover a wide range of inlet concentration ratios between the competing ions. And in all three cases, target anions in the electrosorption cell forms a self-sharpening reaction-diffusion wave front. Based on the model, a three-step stop-flow operation scheme with a pure stripping solution of target anions is proposed that optimizes the ion adsorption performance and increases the purity of the regeneration stream to almost 100%, which is beneficial for downstream processing. [ABSTRACT FROM AUTHOR]

In this paper, the effect of hydrogen ions on the adsorption onto granular activated carbon (GAC) with the inorganic contaminant phosphate, which exists as a form of four species depending on the solution pH, is investigated. Various batch isotherm and kinetic experiments were conducted in an initial pH 4 as an acid, a pH 7 as neutral, and a pH 9 solution as a base for the GAC conditioned with deionized water and hydrochloric acid, referred to as GAC and GACA, respectively. The physical properties, such as the total surface area, pore volume, pore size distribution, and weight of the element, obtained from Brunauer–Emmett–Teller (BET) and scanning electron microscopy coupled with energy-dispersive X-ray spectrometry (SEM–EDX) represent no significant differences. However, the hydrochloric acid (HCl) condition results in an alteration of the pH of the point of zero charge from 4.5 to 6.0. The optimized initial pH was determined as being acid for the GAC and as being neutral for the GACA. According to the Langmuir isotherm, the relatively high Qm was obtained as being acid for the GAC and clearly distinguishes the pH effect as being the base for the GACA. An attempt was made to assess the adsorption mechanism using the pseudo-first-order (PFO), the pseudo-second-order (PSO), and the intraparticle diffusion models. The higher R2 for the PSO in the entire pH range indicated that chemisorption was predominant for phosphate adsorption, and the pH did not change the adsorption mechanism. A prolonged Bed Volume (BV) for the GACA demonstrated that the hydrogen ions on the surface of the GAC enhanced phosphate adsorption. [ABSTRACT FROM AUTHOR]

[Display omitted] • The leaching effect of albite was sorted as follows: hydrochloric acid > potassium hydroxide > deionized water. • The adsorption of H 3 O+, OH− and H 2 O molecules on the surface of albite resulted in the loose framework of albite. • The H+ and K+ in solution exchanged with Na+ in albite and caused the leaching of Na element in albite. The mechanism of inorganic acid and alkali promoted weathering of albite is still unclear. In this work, the mechanism was investigated through leaching experiments and DFT simulations. The results showed that the leaching effect of albite was sorted as follows: hydrochloric acid > potassium hydroxide > deionized water. The H 3 O+ dehydrogenated by breakage of O–H bond, and then the proton bonded with the O atom to form a silicon hydroxyl group on the surface of albite. The O atom in OH− bonded with the three-coordinated Al atom to form the four-coordinated Al. The H 2 O molecule was adsorbed on the surface of albite by hydrogen bond. Meanwhile, the adsorption of H 3 O+, OH− and H 2 O on the (0 0 1) surface of albite caused the elongation of Si–O and Al–O bonds in the bulk phase, resulting in the loose framework of albite. Compared to the interaction mode of water molecules and albite, the H+ in hydrochloric acid and K+ in potassium hydroxide exchanged with Na+ in albite, which caused that the albite lattice was contracted and expanded, respectively. As a result, the surface of albite was damaged, and further caused the Na element was released from the albite crystal to liquid phase. [ABSTRACT FROM AUTHOR]

The adsorption phenomenon on surfaces is investigated both with and without the presence of an external electric field. A simple interpretation of the adsorption coefficient and desorption time, as they appear in Langmuir's isotherm model, is presented. A model for electrosorption is proposed, which explicitly takes into account the applied external voltage and the reaction field resulting from the adsorbed charges. Both saturation, stemming from the finite density of adsorption sites, and non-saturation regimes are considered. The case of a system in contact with a reservoir of particles is also analyzed for its experimental importance. The model's validity is assessed by analyzing experimental data published by several research groups. A comparative study of the proposed model is conducted in relation to the commonly used pseudo-first and pseudo-second order models. Unlike the latter models, the proposed model allows for the assessment of the impact of the external voltage on the model parameters. The model takes into account ion generation resulting from electrolysis phenomena. [Display omitted] [ABSTRACT FROM AUTHOR]

The electro-assisted adsorptive removal of Sr2+ and Cs+ ions from aqueous solution by capacitive deionization (CDI) was studied using activated carbon cloth (ACC) as electrode. Various influencing factors, including initial concentration and the applied voltage, on the removal efficiency of Sr2+ and Cs+ were examined. The results showed that ACC electrode had a large amount of oxygen- and nitrogen-containing functional groups. The removal efficiency of Sr2+ and Cs+ was 40.58% and 62.05%, respectively, which decreased when their initial concentration increased from 3 to 20 mg L−1. The removal efficiency of Sr2+ and Cs+ increased by 26.64% and 17.84% with increase of the applied voltage. CDI process is favorable to remove high valence ions due to the ion-exchange and charge interaction mechanisms. The mixed-order (MO) model could fit the adsorption kinetics of Sr2+ and Cs+ (R2 = 0.938). The Redlich-Peterson isotherm could be used for Sr2+ and Cs+ adsorption. After adsorption, Sr and Cs partly deposited on the surface of the ACC, which did not change the surface structure of the ACC electrode. [ABSTRACT FROM AUTHOR]

Literature reporting temperature and desorption mode as factors of capacitive deionization (CDI) process for water desalination is rare. This study explored the impacts of four water temperatures (15°C, 25°C, 35°C, and 45°C), three salt concentrations (350, 1260, and 3100 mg/L), and three desorption modes (potential removal, short circuit, and polarity reversal) on performance of a 'closed-loop' CDI system. Results showed that a higher temperature promoted adsorption and desorption rates but impaired adsorption capacity. Polarity reversal could greatly expedite the desorption process compared to short circuit and potential removal. A promotional impact of concentration on CDI desalination could be explained by the formation of electrical double layers. The research also noted the earlier occurrence of re-adsorption at higher temperatures during polarity-reversal desorption. Strategies of increasing water temperature on short adsorption cycles and using an adjustable combination mode of polarity reversal and short circuit for desorption are implied for improving desalination efficiency and water recovery of CDI systems. [ABSTRACT FROM AUTHOR]

A review of the literature published in 2019 on topics related to hazardous waste management in water, soils, sediments, and air. The review covered treatment technologies applying physical, chemical, and biological principles for the remediation of contaminated water, soils, sediments, and air. Practical points: This report provides a review of technologies for the management of waters, wastewaters, air, sediments, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) in three scientific areas of physical, chemical, and biological methods.Physical methods for the management of hazardous wastes including general adsorption, sand filtration, coagulation/flocculation, electrodialysis, electrokinetics, electro‐sorption (capacitive deionization, CDI), membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non‐thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed.Chemical methods including ozone‐based, hydrogen peroxide‐based, potassium permanganate processes, and Fenton and Fenton‐like process were reviewed.Biological methods such as aerobic, anoxic, anaerobic, bioreactors, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed.Case histories were reviewed in four areas including contaminated sediments, contaminated soils, mixed industrial solid wastes and radioactive wastes. [ABSTRACT FROM AUTHOR]

By summarizing 187 relevant research articles published in 2019, the review is focused on the research progress of physicochemical processes for wastewater treatment. This review divides into two sections, physical processes and chemical processes. The physical processes section includes three sub‐sections, that is, adsorption, granular filtration, and dissolved air flotation, whereas the chemical processes section has five sub‐sections, that is, coagulation/flocculation, advanced oxidation processes, electrochemical, capacitive deionization, and ion exchange. Practitioner points: Totally 187 research articles on wastewater treatment have been reviewed and discussed.The review has two major sections with eight sub‐topics. [ABSTRACT FROM AUTHOR]

Nanoporous carbon materials are well recognized as the main components of electrodes in capacitive deionization. Herein, the activated carbons were produced based on rice husk which is an abundant waste material in southern regions of Kazakhstan. The resulting carbons were characterized electrochemically by comparing their performance with well-known brands of commercial porous carbons (i.e. Norit DLC Super 30, Kuraray YP 50F). The features of carbon/carbon electrochemical cells were analyzed using the means of galvanostatic cycling with potential limitation and cyclic voltammetry. Whilst the surface morphology and elemental composition of carbons were observed using scanning electron microscopy combined with energy dispersive X-ray spectroscopy. Using the method of low-temperature nitrogen adsorption it has been established that the specific surface of home-made carbon produced based on rice husk is equal to 2290 m²g-1. The salt adsorption analysis has been performed using different concentrations of inlet solutions of sodium chloride. Our study has shown that the manufacturing and application of activated carbons based on rice husk can be highly efficient because the resulting electrode materials exhibit a high electrosorption capacity of 20.02 mg g-1, which exceeds similar values obtained in the case of application of commercial porous carbons. [ABSTRACT FROM AUTHOR]

• A modified configuration for the energy-efficient adsorption desalination method was proposed. • Internal heat recovery achieved within the proposed multi-cycle system. • Considerable amounts of cooling production with two temperature levels were delivered. • 20 % rise in SDWP was observed in comparison to a single-cycle configuration. • Full sensitivity analyses of the system parameters were carried out. Due to the drawbacks of conventional methods of desalination, the adsorption desalination system has been introduced as a replacement with several advantages such as capability of using low-grade waste heat, low cost, and production of cooling as its second output. The aim of the paper is to provide a conceptual theoretical framework based on new advanced adsorption desalination and cooling system configured of double-cycle multi-bed dual-evaporator with internal heat recovery. As an innovative approach, the cycles are coupled through integrated equipment, working as a condenser for one of the cycles and a high-pressure evaporator for the other one. System performance is investigated in terms of specific daily water production (SDWP), low and high-pressure cooling capacities (SCPLP and SCPHP), and overall conversion ratio (OCR). It is shown that not only SDWP of the proposed configuration increases by 20% in comparison to the single-cycle multi-bed dual evaporator system, but also it is capable of producing considerable amounts of two grades of cooling water. The proposed configuration with 9.6 m3 of SDWP along with 24 and 25 Rton/ton of high and low-grade cooling capacities could be a suitable alternative to conventional configurations of adsorption desalination. Furthermore, a full sensitivity analysis is carried out by manipulating several system parameters, and the system performance is evaluated. [ABSTRACT FROM AUTHOR]

In this work, the interactions between simple carbon nanotubes (CNTs) and doped carbon nanotubes (DCNTs; with sulfur, boron, aluminum, silicon, phosphorus, or nitrogen) as good adsorbents with various ions such as Fe2 +, Na +, Ca2 +, Mg2 +, Cl−, CO32−, SO42−, and NO3− were fully considered through density functional theory (DFT), natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) calculations. The adsorption energies (Ead) demonstrated that these ions could be adsorbed on the surface of the CNTs and DCNTs via the exothermic process, especially in the gas phase. QTAIM analysis confirmed that there are non-covalent interactions between these ions and CNT or DCNTs. The calculated energies illustrated that Si-CNTs and B-CNTs have the highest Ead values in the gas and solvent phase, respectively. Moreover, CNTs had the least Ead values in both phases and the best ion with the minimum Ead value in both phases is iron. Finally, population analyses were performed to obtain the reactivity parameters, molecular properties, bonding structural, and density of states (DOS) plots of all structures. [ABSTRACT FROM AUTHOR]

Olive mill wastewater (OMW) is characterized as a high-strength effluent due to the high organic load, low biodegradability, and presence of phytotoxic compounds. Most of the OMW treatment methods proposed, including adsorption, focus mainly on the reduction of chemical oxygen demand and recovery of polyphenols. Adsorption studies aiming at nutrient removal from OMW are very limited. In the present work, Ca(OH)2-treated zeolite (CaT-Z) in a granular form was used for simultaneous recovery of phosphate (PO43−) and potassium (K+) ions from two samples of anaerobically digested OMW. Nutrient adsorption was investigated as a function of contact time, pH and dilution of OMW with deionized water. The lower removal efficiency of phosphorus (P) by CaT-Z was observed at higher dilution ratios consisted of 3.125–6.25% OMW-1 and 5% OMW-2. The maximum P removal was 73.9% in 25% OMW-1 and 85.9% in 10% OMW-2. Potassium removal, as the predominant cation of OMW samples, increased from 17.3 to 46.1% in OMW-1 and from 15.1 to 57.7% in OMW-2 with increasing dilution. The maximum experimental adsorption capacities were 15.8 mg K and 2.14 mg P per gram of CaT-Z. Five sequential treatments of 50% OMW-2 with fresh CaT-Z at each stage ensured a cumulative removal of 87.5% for P and 74.9% for K. Adsorption kinetics were faster for K than for P. The plant-available P was found to be the predominant fraction on the loaded CaT-Z. Electron Probe Micro-analysis confirmed the enhanced content of K and P on the loaded CaT-Z, whereas X-ray mapping revealed the co-distribution of Ca and P. This study demonstrates the potential usage of CaT-Z as an immobilization medium of P and K from anaerobically treated OMW. [ABSTRACT FROM AUTHOR]

Low-cost adsorbents from cassava leaves (CLP) were prepared by simply washing the leaf powder with deionized water. The adsorption of methylene blue (MB) from the aqueous solution was measured in order to examine the adsorbent performance. The effect of the pH of the solution was studied by varying pH from 2 to 10. The kinetics of MB adsorption onto CLP followed the pseudo-second-order kinetic model with a k-value of 0.087907 g mg-1 min-1 and 0.094081 g mg-1 min-1 for CLP before and after washing, respectively. The adsorption isotherm for both adsorbents followed the Langmuir isotherm model with qm values of 178.5 mg g-1 and 243.9 mg g-1. The existence of disturber ions was investigated by adding NaCl into the MB solutions at a variety of concentrations. [ABSTRACT FROM AUTHOR]

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This is a review of the literature published in 2018 on topics related to hazardous waste management in water, soils, sediments, and air. The review covers treatment technologies applying physical, chemical, and biological principles for contaminated water, soils, sediments, and air. Practitioner points: The management of waters, wastewaters, and soils contaminated by various hazardous chemicals including inorganic (e.g., oxyanions, salts, and heavy metals), organic (e.g., halogenated, pharmaceuticals and personal care products, pesticides, and persistent organic chemicals) was reviewed according to the technology applied, namely, physical, chemical and biological methods.Physical methods for the management of hazardous wastes including adsorption, coagulation (conventional and electrochemical), sand filtration, electrosorption (or CDI), electrodialysis, electrokinetics, membrane (RO, NF, MF), photocatalysis, photoelectrochemical oxidation, sonochemical, non‐thermal plasma, supercritical fluid, electrochemical oxidation, and electrochemical reduction processes were reviewed.Chemical methods including ozone‐based, hydrogen peroxide‐based, persulfate‐based, Fenton and Fenton‐like, and potassium permanganate processes for the management of hazardous were reviewed.Biological methods such as aerobic, anaerobic, bioreactor, constructed wetlands, soil bioremediation and biofilter processes for the management of hazardous wastes, in mode of consortium and pure culture were reviewed. [ABSTRACT FROM AUTHOR]

Bioelectrochemical system is a prospective strategy in organic-contaminated groundwater treatment, while few studies clearly distinguish the mechanisms of adsorption or biodegradation in this process, especially when dense biofilm is formed. This study employed a single chamber microbial electrolysis cell (MEC) with two three-dimensional electrodes for removing a typical organic contaminant, 2,4-dichlorophenol (DCP) from groundwater, which inoculated with anaerobic bacteria derived from sewage treatment plant. Compared with the single biodegradation system without electrodes, the three-dimensional electrodes with a high surface enabled an increase of alpha diversity of the microbial community (increased by 52.6% in Shannon index), and provided adaptive ecological niche for more bacteria. The application of weak voltage (0.6 V) furtherly optimized the microbial community structure, and promoted the aggregation of microorganisms with the formation of dense biofilm. Desorption experiment proved that the contaminants were removed from the groundwater mainly via adsorption by the biofilm rather than biodegradation, and compared with the reactor without electricity, the bioelectrochemical system increased the adsorption capacity from 50.0% to 74.5%. The aggregated bacteria on the surface of electrodes were mainly dominated by Delftia tsuruhatensis (85.0%), which could secrete extracellular polymers and has a high adsorption capacity (0.30 mg/g electrode material) for the contaminants. We found that a bioelectrochemical system with a three-dimensional electrode could stimulate the formation of dense biofilm and remove the organic contaminants as well as their possible more toxic degradation intermediates via adsorption. This study provides important guidance for applying bioelectrochemical system in groundwater or wastewater treatment. [Display omitted] • Bioelectrochemical system was used to treat chlorophenol-contaminated groundwater • External electricity led to the aggregated biofilm on three-dimensional electrode • The dense biofilm enhanced the adsorption of chlorophenols from 50% to 74.5% • The aggregations on electrode were dominated by Delftia tsuruhatensis (85%) • Delftia tsuruhatensis was enriched for the first time in bioelectrochemical system [ABSTRACT FROM AUTHOR]

• Aggregates swell due to the "adsorption-swelling" and "adsorption-filling" effects. • The "adsorption-swelling" effect was most prominent with fraction size 2 ∼ 1 mm. • The "adsorption-filling" effect was most prominent with fraction size < 0.053 mm. Soil aggregates swell when infiltrated by water, and their size can increase in two ways. First, aggregates can attach to one another with water acting as a bridge (i.e., adsorption), and water can enter the aggregate pores (i.e., swelling). This is defined as the "adsorption-swelling" effect. Second, clay can fill the pores of macroaggregates and microaggregates (i.e., filling) when adsorption occurs. This is defined as the "adsorption-filling" effect. However, the size range of aggregates affected by these effects and the extent of their influence on aggregate swelling are still unclear. Therefore, different initial size fractions (5 ∼ 2, 2 ∼ 1, 1 ∼ 0.5, 0.5 ∼ 0.25 and 0.25 ∼ 0.053 mm) of soil aggregates from the black soil zone of Northeast China were studied. The size range of swollen aggregates, the "adsorption-swelling" rate (V) of initial size fractions, and the "adsorption-filling" rate (E) of size fractions < 0.053 mm were measured and calculated in three experimental treatments that involved the following procedures: i) wet-sieving of each initial size fraction in deionized water (WS); ii) wet-sieving of each initial size fraction of air-dried aggregates after they were soaked in absolute ethanol (WS as); and iii) the size fraction < 0.053 mm air-dried aggregates were mixed with each initial size fraction of air-dried aggregates in absolute ethanol and then wet-sieved (WS af). The results were as follows: i) the size fraction 2 ∼ 0.053 mm were swollen. ii) V decreased exponentially with decreasing initial particle size, with a maximum value of 32.30% at a size fraction of 2 ∼ 1 mm; and iii) the "adsorption-filling" effect of size fraction < 0.053 mm was obvious in the size fraction < 2 mm swelling aggregates with a maximum of 29.54%. The "adsorption-swelling" and "adsorption-filling" effects had greater impacts on soils with high contents of the size fractions 2 ∼ 1 and < 0.053 mm. This study provides a theoretical basis for understanding the swelling mechanisms of soil aggregates. [ABSTRACT FROM AUTHOR]

One of the topics gaining lots of recent attention is the antimony (Sb) pollution. We have designed a dual-functional electroactive filter consisting of one-dimensional (1-D) titanate nanowires and carbon nanotubes for simultaneous oxidation and sorption of Sb(III). Applying an external limited DC voltage assist the in-situ conversion of highly toxic Sb(III) to less toxic Sb(V). The Sb(III) removal kinetics and efficiency were enhanced with flow rate and applied voltage (e.g., the Sb(III) removal efficiency increased from 87.5% at 0 V to 96.2% at 2 V). This enhancement in kinetics and efficiency are originated from the flow-through design, more exposed sorption sites, electrochemical reactivity, and limited pore size on the filter. The titanate-CNT hybrid filters perform effectively across a wide pH range of 3–11. Only negligible inhibition was observed in the presence of nitrate, chloride, and carbonate at varying concentrations. Our analyses using STEM, XPS, or AFS demonstrate that Sb were mainly adsorbed by Ti. DFT calculations suggest that the Sb(III) oxidation kinetics can be accelerated by the applied electric field. Exhausted titanate-CNT filters can be effectively regenerated by using NaOH solution. Moreover, the Sb(III)-spiked tap water generated ∼2400 bed volumes with a >90% removal efficiency. This study provides new insights for rational design of continuous-flow filters for the decontamination of Sb and other similar heavy metal ions. Image 1 • A dual-functional electroactive filter system enabled Sb(III) oxidation and sorption. • Sb(III) removal kinetics and efficiency enhanced with flow rate and applied voltage. • Applied electric field accelerated the Sb(III) oxidation process. • Exhausted titanate-CNT filter can be effectively regenerated by chemical washing. [ABSTRACT FROM AUTHOR]

Chlorpheniramine is a pharmaceutical pollutant and a precursor of carcinogenic nitrosamines during disinfection/oxidation. In our previous study, graphene oxide coated with magnetite (GO-Fe3O4) was capable of removing chlorpheniramine in deionized water by adsorption. This study investigated the removal of chlorpheniramine and its nitrosamine formation potentials (FPs) by adsorption onto magnetic GO-Fe3O4, with respect to the influence by using real municipal wastewaters as the background. In the results, the adsorption performances of chlorpheniramine in wastewaters decreased in the order: GO-Fe3O4 suspension > GO-Fe3O4 particles > activated carbon. Chlorpheniramine adsorptions on GO-Fe3O4 particles and activated carbon were reduced by using real wastewaters as the background, whereas chlorpheniramine adsorption on GO-Fe3O4 suspension was enhanced due to the effects of surface charge on GO-Fe3O4 and ionic strength variation in water. The fittings of adsorption isotherms indicated that the wastewater background reduced the surface heterogeneity of GO-Fe3O4 suspension and improved the adsorption performance. Appreciable removal efficiencies of NDMA and other nitrosamine FPs were observed when GO-Fe3O4 particles were added in real wastewaters. However, when chlorpheniramine was present in wastewaters, chlorpheniramine adsorption and degradation reaction simultaneously occurred on the surface of GO-Fe3O4, increasing NDMA and other nitrosamine FPs in wastewaters after GO-Fe3O4 addition for chlorpheniramine adsorption. The assumption was further demonstrated by observing the NDMA-FP increase during chlorpheniramine adsorption on GO-Fe3O4 in deionized water. GO-Fe3O4 is a potential adsorbent for chlorpheniramine removal. Nevertheless, the low treatment efficiencies at high doses limit its application for nitrosamine FP adsorptions in real wastewaters. [ABSTRACT FROM AUTHOR]

Abstract The adsorption and desorption behavior of Cr(VI) in membrane capacitive deionization (MCDI) was investigated systematically in the presence of bovine serum albumin (BSA) and KCl with different concentrations, respectively. Results revealed that Cr(VI) absorption was enhanced and the adsorption amount for Cr(VI) increased from 155.7 to 190.8 mg/g when KCl concentration increased from 100 to 200 mg/L in the adsorption process, which was attributed to the stronger driving force. However, the adsorption amount sharply decreased to 90.2 mg/g when KCl concentration reached up to 1000 mg/L suggesting the negative effect for Cr(VI) removal that high KCl concentration had. As for the effect of BSA on ion adsorption, the amount for Cr (VI) significantly declined to 78.3 mg/g and pH was found to be an important factor contributing to this significant reduction. Then, the desorption performance was also conducted and it was obtained that the presence of KCl had negligible effect on Cr(VI) desorption, while promoted by the addition of BSA. The incomplete desorption was obtained and the residual chromium ions onto the electrode after desorption was detected via energy-dispersive X-ray spectroscopy (EDS). Based on above analysis, the enhanced removal mechanism for Cr(VI) in MCDI was found to be consisted of ion adsorption onto electrode surface, the redox reaction of Cr(VI) into Cr(III) and precipitation, which was demonstrated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Abstract Electrochemical oxidation is an effective mean to degrade non-biodegradable organics from the contaminated waters. However, its current efficiency is very low for the low-concentration organic pollutants treatment. In this work, combining with the outstanding adsorption property of CNT and the effective electrocatalytic oxidation performance of β-PbO 2 , we constructed novel layer-by-layer carbon nanotube/PbO 2 anodes (CNT/PbO 2 -3, CNT/PbO 2 -4 and CNT/PbO 2 -5) with high adsorbability to enhance the electrochemical degradation efficiency of low-concentration sodium pentachlorophenate (PCP Na). In electrochemical oxidation tests, the PCP-Na was rapidly enriched in the CNT/PbO 2 film through adsorption/electrosorption and then efficiently degraded in site. The removal efficiency of low-concentration PCP-Na (5 mg/L) on CNT/PbO 2 -4 reached 73.8% after only 5 min of electrolysis, whereas that on pure PbO 2 was only 9.9%. To further clarify the mechanism of improvement of PCP-Na removal on CNT/PbO 2 -4 anode, the generation capacity of·OH radicals, oxygen evolution overpotential, voltammetric charge quantity, interface resistance, and specific surface area of CNT/PbO 2 -4 anode were also assessed and compared with those of other three anodes. Results showed that, in addition to the synergistic effect of adsorption/electrosorption and electrocatalysis, the more active sites, smaller electron transfer resistance and higher direct oxidation capacity of CNT/PbO 2 -4 anode also contributed to improving degradation rate of PCP-Na on CNT/PbO 2 -4 anode. Additionally the electrochemical degradation pathway of PCP-Na was also proposed based on the gas chromatography-mass spectrometry analysis. Finally, CNT/PbO 2 -4 electrode exhibited longer accelerated lifetime of 116 h than pure PbO 2 electrode (91 h). Thus, these findings provide a new anode to improve the removal of low-concentration organic pollutants through combining electrochemical oxidation and adsorption/electrosorption processes. Graphical abstract Image 1 Highlights • A novel layer-by-layer CNT/PbO 2 anode was fabricated. • The degradation efficiency of PCP-Na on CNT/PbO 2 anode was obviously improved. • The low-concentration PCP-Na was enriched on the surface CNT/PbO 2 anode. • Adsorption/electrosorption and electrocatalysis were combined. [ABSTRACT FROM AUTHOR]

Abstract: Multiwalled carbon nanotubes (MWCNTs) were treated by nitric acid to probe the effect of nitric acid modification on their properties and desalination performance in capacitive deionization (CDI). The nitric acid modification exerts a slight influence on the morphologies, specific surface area, and pore properties of the MWCNTs but can increase the amount of oxygen‐containing functional groups and then obviously enhance the specific capacitance of the electrodes. Thus, the desalination efficiency can be significantly improved as the modified MWCNTs serve as electrodes in CDI. The adsorption of salt ions on the original and modified MWCNT electrode is fitted well by the Freundlich isotherm other than the Langmuir isotherm. [ABSTRACT FROM AUTHOR]