Application In Wastewater Purification Research Articles

A Method to Design and Optimize Axial Flow Cyclones for Gas–Liquid Separation

Abstract This article provides a detailed design guide, optimization, and performance assessment for air–water separation of an axial flow cyclone. Axial flow cyclones (also known as swirl tube demisters, mist eliminators, or Austin–Write cyclones) have a range of applications in several different industries. This method of gas–liquid separation offers many benefits. Among these are high liquid separation efficiencies (near 99%) and an inline design that allows them to be more easily fitted into existing piping structures. Despite these benefits, there are several design parameters that have not been optimized for performance in wastewater purification applications. This research fills the gap in the literature by quantifying the effect of new design parameters on water collection efficiency, ηwater collection, and the air bypass efficiency, ηair bypass, defined as the ratio of the air mass flowrate exiting through the desired air outlet over the inlet air mass flowrate. A set of wide-ranging experiments were conducted to study the effects of gas–liquid flow rates, tube geometry, and relative injection angles to optimize the water collection and air bypass efficiencies. The water collection efficiency exceeded 99.8% when the liquid streamline came in direct contact with the water drainage exit. An empirical correlation was developed to predict the swirl pitch as a function of the above design parameters. Predictions from the correlation were within 10% of the experimental results. The correlation can be used to design highly efficient in-line gas–liquid separators.

Chitosan-Based Nanocomposite Polymeric Membranes for Water Purification-A Review.

During the past few years, researchers have focused their attention on developing innovative nanocomposite polymeric membranes with applications in water purification. Natural and synthetic polymers were considered, and it was proven that chitosan-based materials presented important features. This review presents an overview regarding diverse materials used in developing innovative chitosan-based nanocomposite polymeric membranes for water purification. The first part of the review presents a detailed introduction about chitosan, highlighting the fact that is a biocompatible, biodegradable, low-cost, nontoxic biopolymer, having unique structure and interesting properties, and also antibacterial and antioxidant activities, reasons for using it in water treatment applications. To use chitosan-based materials for developing nanocomposite polymeric membranes for wastewater purification applications must enhance their performance by using different materials. In the second part of the review, the performance’s features will be presented as a consequence of adding different nanoparticles, also showing the effect that those nanoparticles could bring on other polymeric membranes. Among these features, pollutant’s retention and enhancing thermo-mechanical properties will be mentioned. The focus of the third section of the review will illustrate chitosan-based nanocomposite as polymeric membranes for water purification. Over the last few years, researchers have demonstrated that adsorbent nanocomposite polymeric membranes are powerful, important, and potential instruments in separation or removal of pollutants, such as heavy metals, dyes, and other toxic compounds presented in water systems. Lastly, we conclude this review with a summary of the most important applications of chitosan-based nanocomposite polymeric membranes and their perspectives in water purification.

Graphene Oxide and Graphene Oxide-TiO₂ Nanocomposites: Synthesis, Characterization, and Rhodamine B Photodegradation Investigation.

In this study, graphene oxide (GO) sheets were successfully synthesized using two routes: conventional Hummers' (HGO) and modified Hummers' (or Marcano's) (MGO) methods. GO sheets were then assembled with TiO₂ nanoparticles to form nanocomposites (i.e., HGO-TO and MGO-TO). The properties of HGO and MGO and their nanocomposites with TiO₂ were evaluated by Fouriertransform infrared (FTIR), Raman, ultraviolet-visible (UV-Vis) adsorption, and diffuse reflectance (DRS) spectroscopies, X-ray diffraction (XRD), and thermal gravimetric analysis (TGA). The specific surface area, pore volume, and pore size of MGO, determined by Brunauer-Emmett-Teller (BET) equation, were 565 m²g-1, 376 cm³ g-1, and 30 nm, respectively; all of these parameters decreased after MGO was combined with TiO₂. In addition, compared with HGO, MGO possessed higher oxidation level and more stable bonding with TiO₂ nanoparticles. The morphology of HGO and MGO, which were characterized by scanning electron (SEM) and transmission electron microscopies (TEM), together with energy-dispersive X-ray (EDX) spectroscopy and elemental mapping technique, was determined to consist of TiO₂ nanoparticle-assembled GO sheets. All GO-TiO₂ nanocomposite samples exhibited a very high activity (˜100%) toward rhodamine B (RhB) dye photodegradation under natural sunlight exposure within 60 min. The obtained results for the GO-TiO₂ nanocomposite showed the potential of its application in wastewater purification and other environmental aspects.

Poly(p-phenylene benzobisoxazole) nanofiber/reduced graphene oxide composite aerogels toward high-efficiency solar steam generation

Interfacial solar steam generation is emerging as a promising high-efficiency strategy to produce clean water by harvesting and converting clean solar energy to the localized heat. It is highly desirable to introduce robust materials that are able to bear the extreme conditions for advanced applications of solar steam generation. Here, we demonstrate an all-in-one interfacial solar evaporator made from poly(p-phenylene benzobisoxazole) nanofiber (PBONF)/graphene oxide (GO) and PBONF/reduced graphene oxide (RGO) composite aerogels with high porosity, robust mechanical properties, and excellent thermal insulation performance. The evaporators of PBONF/RGO composite aerogel show fast and durable solar-vapor conversion with a high efficiency of 98.4 % under unconcentrated one sun irradiation. The PBONFs not only reinforce the mechanical properties of composite aerogels, but also affords them great potential applications in wastewater purification in some extreme environment, for instance, aerospace.

Controlled synthesis of carbon nitride-TiO2 nanocomposites for prompt photocatalytic degradation of individual and mixed organic dyes at room temperature

Development of efficient and low-cost photocatalysts for the degradation of mixed organic dyes in water resources is of great importance in various industrial and environmental applications. Herein, we prepared organic-inorganic nanocomposites including a carbon nitride and TiO2 (0.1CNTi) without and with reduced graphene oxide denoted as 0.1rGOCNTi using the modified hydrothermal method. The TiO2 and composite catalysts 0.1rGOCNTi and CNTi were well characterized previously using FT-IR, Raman spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectra (DRS). The photocatalytic oxidation performances of typically prepared 0.1rGOCNTi and 0.1CNTi nanocomposites were investigated towards methylene blue (MB), Rhodamine B (RhB), and Rhodamine 6G (Rh6G) (individually and mixed) at room temperature under Xe lamp illumination in the presence of H2O2 along with the in situ electrogenerated O3. Interestingly, the degradation percentage of the individual and mixed dye solution on the synthesized nanocomposites reached over 90% within 5 min and 20 min, respectively, with a slight superior activity for 0.1CNTi than 0.1rGOCNTi. The presented study may open new gates for fabrication of CNTi-based nanocomposites for wastewater purification applications.

Polydopamine Microsphere-Incorporated Electrospun Fibers as Novel Adsorbents for Dual-Responsive Adsorption of Methylene Blue.

The usually inconvenient detection and uneasy recycling of polydopamine (PDA) with sphere morphology as an adsorbent restrict its actual applications in wastewater purification. Thus, novel composite fibers were fabricated via the electrospinning technique by integrating polydopamine microspheres (PDA-MPs) with pH/temperature dual-responsive copolymers. The insoluble fraction of the fabricated composite fibers can be maintained to a value above 89% after being immersed in aqueous solutions with different pH values. Also, the regeneration efficiency of the composite fibers can also remain above 80% after undergoing five adsorption-desorption cycles. These results both indicated that the fabricated composite fibers can avoid secondary pollution during the adsorption process effectively. In addition, the presence of abundant N-isopropyl acrylamide (NIPAM) units within the fibers could make it have a relatively higher water swelling ability of 4643%, which could further offer relatively larger inner spaces to accommodate the dye molecules. Meanwhile, by incorporating β-cyclodextrin (β-CD), methacrylic acid (MAA), PDA, and NIPAM components, plentiful active adsorption sites could be supplied to interact with methylene blue (MB) dye. So, the adsorption experiments of the composite fibers showed a maximum adsorption capacity of 1722.1 mg/g at pH 9.0 and a temperature of 55 °C. Furthermore, the pseudo-second-order kinetic model of adsorption suggested that it is a chemisorption process. Moreover, the adsorption experimental data can be better described by Langmuir models, inferring its monolayer adsorption. The adsorption thermodynamic studies revealed that adsorption is a spontaneous and endothermic process. Also, the increase of temperature facilitated the adsorption processes, owing to the increase of adsorbent's hydrophobicity and molecules' reactivity. The present work suggested that the combination of smart-responsive polymers and PDA-MPs could form an unprecedented system to be a promising candidate adsorbent for wastewater treatment.

Mixed solvent based surface modification of CuS nanostructures for an excellent photocatalytic application

A variety of high-quality, shape and size consistent nanostructures of copper sulfide (CuS) in the form of hierarchical architectures composed of intersecting nano-sheets have been fabricated via mixed solvent route. Copper chloride and thiourea have been utilized as precursors for copper and sulfur sources for each experimentation in the presence of a variety of mixed solvents to obtain various morphologies of CuS. The prepared products have been characterized by X-ray powder diffraction (XRD) and all of the synthesized products have been investigated to be the phase pure single crystalline. Scanning Electron Microscopy (SEM) revealed the well-ordered and isolated particles. The Energy Dispersive Spectroscopy (EDS) spectrum further proved that the obtained products in all of the synthetic processes don’t contain any kind of impurity. Ultraviolet– visible–near infrared (UV–vis–NIR) transmittance spectrophotometer has been utilized to ascertain the optical properties of the as prepared nanostructures. An extended U.V absorption in near-IR region, indicate the covellite phase of CuS. Most importantly, the synthesized nanostructures demonstrated an excellent photo-catalyst response in degrading highly concentrated rhodamine B (RhB) dye aqueous solutions under visible light irradiation along with an excellent reusability, suggesting a promising application in wastewater purification. The excellent photo-catalytic activity has been attributed to surface hierarchical structure with good absorbing and adsorbing properties, high visible light utilization and low electron hole recombination rate.

TiO2-coated copper zinc tin sulfide photocatalyst for efficient photocatalytic decolourization of dye-containing wastewater

A hierarchical composite of TiO2 coated on Cu2ZnSnS4 (CZTS/TiO2) with various molar ratios was synthesized by hydrothermal process combined with subsequent grinding and low-temperature calcination. The optimal molar ratio of CZTS to TiO2 in CZTS/TiO2 composites is 1:1. Due to the staggered band structure of CZTS and TiO2, the designed CZTS/TiO2 superstructure extends the light absorption of TiO2 into visible region and even separates photoinduced carriers well so that it presented higher photocatalytic activity than pristine CZTS and anatase TiO2. The photodegradation efficiency (PE) of aqueous RhB solution (10 mg/L) reached 95.04% with 120 min. Furthermore, the photodegradation reaction obeyed the first-order kinetics, which the apparent rate constant (kapp) was 4.87 and 2.70 times higher than that of pure CZTS and TiO2, respectively. More importantly, the synthesized CZTS/TiO2 composites exhibited excellent durability and recyclability in the photocatalytic process. Even after using for four times, the photocatalytic activity was hardly any decay. The PE decreased significantly with increasing pH of dye solutions. At pH of 2–6, at least 85% of the dye solution was degraded. Studying critical role of h+ and •O2− radicals involved in RhB decomposition. The results indicates that CZTS/TiO2 photocatalyst could act as a perspective candidate in wastewater purification applications.

Compressible nanowood/polymer composite adsorbents for wastewater purification applications

Heavy metal pollution has raised serious concerns due to the potential threat to public health and the environment. Adsorption is an important method for removing metal ions from wastewater, but many current adsorbents are limited by high cost, low adsorption efficiency and poor cyclability. Herein, a compressible composite (PEI-NW) with a porous structure is prepared by a simple chemical treatment of nanowood (NW) with polyethyleneimine (PEI). Modification of NW with PEI enables the efficient adsorption of metal ions. PEI-NW shows excellent adsorption efficiency. Adsorbed heavy metal ions can be rapidly desorbed by simply immersing PEI-NW in a desorption solution. PEI-NW can be reused by employing the squeezing method because of its excellent compressibility. The adsorbent can remove the heavy metal ions from polluted water with 60% of adsorption efficiency even after 50 adsorption-desorption cycles. This compressible composite provides new insights for the design of efficient cleaners for heavy metal ion removal and offers approaches to the development of functionalization of biomass-based composites.

1D hierarchical CdS NPs/NiO NFs heterostructures with enhanced photocatalytic activity under visible light irradiation

One-dimensional (1D) hierarchically structured CdS nanoparticles (NPs)/NiO nanofibers (NFs) heterostructures with remarkable removal efficiency for diazo dye Congo red (CR) were fabricated by a stepwise synthesis process, which was involved a chemical bathing deposition combined with calcination, and a microwave-assisted wet chemical reaction. The crystal phases, morphologies, optical absorption properties, and adsorption/photocatalytic activity of as-prepared products were investigated by XRD, FESEM, TEM, high-resolution TEM (HRTEM), N2 adsorption/desorption isotherms, UV–Vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) spectrum respectively. The experimental results indicated that binary satellite- core CdS NPs/NiO NFs heterojunctions are comprised of n-type CdS NPs with size of 10–30 nm decorated onto 1D p-type NiO NFs with diameter of 60–180 nm and length up to microns, which are self-assembled by nanoparticles with 30–100 nm in size. The possible formation mechanism for satellite-core structured CdS/NiO heterojunction is proposed. Interestingly, the decolorization efficiency over CdS/NiO heterostructures reached up to 91.2% in removal of aqueous CR at high concentration within 40 min under visible light irradiation, which was approximately 5.2 and 3.8 times as high as that of pure CdS nanocrystals (NCs) and the mixture of NiO NFs and CdS NCs. Furthermore, the possible photocatalytic mechanism was also investigated. The as-designed hybrid CdS NPs/NiO NFs heterostructures exhibited improved photocatalytic activity, which is attributed to the enhancement of the visible light adsorption, the efficient separation of photogenerated electrons and holes, and the high adsorption capacity towards CR molecules, thereby displaying superior visible- light-driven photodegradation of CR in high concentration. This work may provide a green engineering heterojunction technology to develop the advanced multifunctional nanocomposites for their applications in wastewater purification.

Cellulose Membrane Composited with ZIF‐8 for Selective Separation of Rhodamine B

AbstractA composite membrane was prepared by in‐situ synthesis of ZIF‐8 on cellulose matrix in alkali/urea system. SEM revealed that ZIF‐8 particles are uniformly dispersed and tightly wrapped around the regenerated cellulose membrane which features a three‐dimensional porous structure. XRD, XPS and IR demonstrated the successful synthesis of ZIF‐8 on cellulose. Dye filtration experiments revealed high rejection rate (96 %) and selectivity for rhodamine B. Moreover, the composite membrane exhibited good cycling behavior with the rejection rate staying over 84 % after five cycles. The finding in this work provides a strategy for the rational design and fabrication of composite materials of cellulose and MOFs with promising application for wastewater purification.

Reduced Graphene Oxide/Zinc Oxide Nanocomposite: From Synthesis to its Application for Wastewater Purification and Antibacterial Activity

Currently, wastewater treatment is one of the most important issues related to the toxic effects of the pathogens and hazardous water pollution impact on human beings, agriculture and animals. In this study, we synthesized reduced graphene oxide/zinc oxide (rGO/ZnO) nanocomposite using a chemical method. The synthesized rGO/ZnO nanocomposite was characterized by XRD, SEM, EDX, FT-IR and UV–Vis spectroscopy. The rGO/ZnO nanocomposite was analyzed for reduction of methylene blue (MB) and 4-nitrophenole (4-NP). The antibacterial activity of GO and rGO/ZnO was also analyzed. The degradation rate of MB under UV lamp by rGO/ZnO nanocomposite was found to be 80% after 5 h. The reduction of 4-NP into 4-aminophenol (4-AP) was completed in 10 min in the absence of reducing agent, whereas in the presence of reducing agent (NaBH4), the reduction time was reduced to 3 min. Furthermore, rGO/ZnO nanocomposite was also analyzed for anti-bacterial activity on Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli bacterial strains using agar well disk diffusion method. The results of anti-bacterial activity showed that rGO/ZnO nanocomposite exhibits better anti-bacterial activity than GO. This indicated the increased biocompatibility of the rGO/ZnO nanocomposite than GO. It was found that rGO/ZnO nanocomposites has great potential for reduction of 4-NP to 4-AP, shows superior antibacterial activity and can be used for biomedical application.

Removal of Methylene Blue Dye Using Metal-Free g-C<sub>3</sub>N<sub>4</sub> Photocatalyst over Natural Sunlight Irradiation

This work presented the high activity of metal-free g-C3N4 photocatalyst for methylene blue (MB) removing over natural sunlight irradiation. These g-C3N4 photocatalysts materials were synthesized by a conventional thermal condensation method using melamine as a precursor under treated at the various annealing temperatures (450 °C, 500 °C, 550 °C, 600 °C and 650 °C). All as-synthesized samples were characterized and confirmed by a several techniques, such as, X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), UV-vis diffuse reflectance spectrometer (DRS), scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), and Brunauer-Emmett-Teller (BET) specific surface area. XRD and FTIR results confirmed that the as-synthesized g-C3N4 samples were completely synthesized at annealing temperature of 500 °C. SEM images showed the morphologies of the g-C3N4 samples had more flake-like structures upon the increasing of annealing temperatures. While DRS results indicated that the absorption edges of as-synthesized g-C3N4 samples were shifted to visible-light region, except the sample as-synthesized at 650 °C (g-C3N4-650 °C). Moreover, the photocatalytic properties of metal-free g-C3N4 photocatalyst materials were evaluated by degrading of MB dye solution under natural sunlight irradiation for 100 min. The results revealed that the highest photocatalytic activity was exhibited by the sample synthesized at 600 °C, which the apparent rate constant (kapp.) was 0.0291 min-1. The orders of activities as: g-C3N4-600 °C > g-C3N4-650 °C > g-C3N4-550 °C > g-C3N4-500 °C > g-C3N4-450 °C. Hence, the metal-free g-C3N4 photocatalyst appears to be an attractive-material for water or wastewater purification applications over activated by sunlight irradiation.

Porous composite architecture bestows Fe-based glassy alloy with high and ultra-durable degradation activity in decomposing azo dye

Since the treatment of wastewater containing azo dye presents problems worldwide, it is important to seek effective materials and technology for the purification of wastewater containing azo dye. Fe-based metallic glasses have been identified as promising materials for the decomposition of dyeing wastewater due to their high chemical activity resulting from their amorphous structure. It is imperative to further improve their degradation performance, and especially their durability, for potential application in wastewater purification. Here, composite structures constructed of porous Ni and amorphous Fe78Si9B13 powder with markedly enhanced degradation performance in Orange II solution were obtained by utilizing a magnet. Due to the favorable effects of structural electrocatalysis and high dispersity of the distinctive porous architecture in addition to its self-cleaning properties, the solid-liquid interface exhibited strong, continuous electrical and mass transport, and a compelling improvement in degradation performance was achieved. Based on degradation tests and spectrum analysis, the kinetic rate was improved over 11-fold. Moreover, ultra-high durability over 100 cycles was revealed in cycling tests. The results indicate that wastewater degradation performance can be greatly enhanced by properly combining Fe-based metallic glasses with porous material.

Construction of magnetic bifunctional β-cyclodextrin nanocomposites for adsorption and degradation of persistent organic pollutants

Herein, we report a novel magnetic bifunctional β-cyclodextrin nanocomposite (Fe3O4@β-CD-CDI) based on metal coordination, which may be used for adsorption and degradation of persistent organic pollutants in aqueous solution. More importantly, N,N’-carbonyldiimidazole (CDI) functionalized β-CD ligand (β-CD-CDI) was assembled on the surface of Fe3O4 by Zn-N interaction. The results of kinetic and isothermal adsorption model investigation indicated that the adsorption rate and capacity of Fe3O4@β-CD-CDI were better than other materials, suggesting the effective accessibility of adsorption sites. We further confirmed that Fe3O4@β-CD-CDI can be used as heterogeneous catalyst to remove BPA through Fenton-like reaction in the presence of hydrogen peroxide (H2O2). Moreover, the material effectively alleviated the secondary pollution owing to the existence of β-CD inner cavity. This study indicated that the magnetic Fe3O4@β-CD-CDI material has great potential applications in wastewater purification containing persistent organic pollutants.

CTAB decorated SnO2 nanosheet assembled micro-flowers for photocatalysts

In this work, CTAB decorated SnO2 nanosheets are synthesized by a simple hydrothermal method. The effect of CTAB on the morphology and photocatalytic performance of SnO2 micro-flowers is investigated, revealing that CTAB played a significant role in the formation of SnO2 micro-flowers. In addition, the photocatalytic performance of SnO2 nanosheet assembled microflowers is characterized through the degrading of methylene blue, erosin and rhodamine B dyes. The as-prepared SnO2 nanosheet assembled micro-flowers have exhibited superior photocatalytic activity and excellent stability, which could be contributed to the unique self-assembled micro-flower structure. This suggests that the as-synthesized SnO2 micro-flowers may have great potential for wastewater purification applications.

Solvothermal ion exchange preparation of Bi11VO19 to sensitize TiO2 NTs with high photoelectrochemical performances

Ag3VO4 nanograss was deposited on the surface of vertically grown TiO2 nanotube arrays (TiO2 NTs) by a successive ion layer adsorption and reaction (SILAR) method, and the Ag3VO4 nanograss was further transformed into Bi11VO19 by the solvothermal ion exchange method. The formation of Bi11VO19 was influenced by solvothermal intervals, and the TiO2 NTs/Bi11VO19 exhibited outstanding visible light response and photoelectrochemical activity. The TiO2 NTs/Bi11VO19 (3) prepared with solvothermal treatment for 3 h showed the optimal photoelectric conversion and photoelectrocatalytic (PEC) properties. The transient photocurrent density, photovoltage and charge carrier concentration achieved 9.53 mA/cm2, −0.29 V and 1.36 × 1020 cm−3, respectively. Furthermore, the PEC rate constants of TiO2 NTs/Bi11VO19 (3) for the MO, RhB and MB degradation achieved 3.56 × 10−3, 9.01 × 10−3 and 2.30 × 10−2 min−1, respectively. The PEC removal efficiency of Cr(VI) was 86.62%. The outstanding photoelectric activity drives the TiO2 NTs/Bi11VO19 photoelectrode prospective applications in waste-water purification and solar cells.

Ultrathin BiOCl/nitrogen-doped graphene quantum dots composites with strong adsorption and effective photocatalytic activity for the degradation of antibiotic ciprofloxacin

Photocatalysis, as a green chemical technology for the removal of antibiotics, has attracted great interest recently. This study proposed a facile one-step hydrothermal process to fabricate ultrathin two dimensional (2D) BiOCl/nitrogen-doped graphene quantum dots (BiOCl/NGQDs) composites. Compared to pure BiOCl, the BiOCl/NGQDs composites exhibited enhancement in both adsorption and photodegradation for antibiotic ciprofloxacin (CIP). The optimized content of NGQDs was 6.9% and this optimized composite showed a degradation efficiency of 82.5% within 60 min under visible-light irradiation, which was considerably better than that of pure BiOCl (34.9%). Meanwhile, most of CIP was efficiently mineralized into CO2, H2O and other inorganic products, as revealed by a total organic carbon (TOC) removal efficiency of 95.5% within 5 h. The improved photocatalytic activity was attributed to excellent adsorption capability, enhanced visible-light response and efficient separation of the photoinduced electron-hole pairs in BiOCl/NGQDs composite. The active species trap experiments and electron spin resonance revealed that O2− and hole mainly participated in the CIP degradation process. Such an effective strategy to design ultrathin 2D composite photocatalysts would provide a new approach for application in wastewater purification.

Synthesis of a cross-linked cellulose-based amine polymer and its application in wastewater purification.

A cross-linked cellulose-amine polymer composed of nanocrystalline cellulose and 1,4-pheneylnediamine was synthesized, and its application as an adsorbent of metal ions from wastewater was dementated. The nanocrystalline cellulose was generated from an olive industry solid waste. The cross-linked polymer analysis results of FTIR, NMR, TEM, SEM, and XRD were generated. The adsorption efficiency of the cellulose-amine polymer toward Cu(II) and Pb(II) was investigated as a function of adsorbent dose, temperature, pH, and time. The adsorption parameters that lead to an excellent adsorption efficiency were determined. The polymer also showed an excellent extraction efficiency toward 20 metal ions present in a sewage sample. The various functional groups present on polymer surface such as amino, hydroxyl, and aryl played a crucial role on metal adsorption. Thermodynamic analysis results support the high efficiency of the polymer toward the metal ions. Kinetic study results reveal that the adsorption process fits well with the pseudo-second-order model and the adsorption isotherm follows a Langmuir isotherm model.

Synthesis of layered double hydroxide from asbestos-containing waste and its adsorption property

Asbestos-containing waste is potentially harmful, and this study proposed a method to prepare layered double hydroxide using acid leaching solution of asbestos-containing waste as resource. This method can effectively reduce the harmful effects of asbestos-containing waste, and the product has wider application prospects. The as-prepared layered double hydroxide is examined by XRD, SEM, FT-IR, TG–DSC and N2 adsorption/desorption isotherms. XRD characterization showed that the layered double hydroxide has been successfully prepared, and other characterizations confirmed the layered double hydroxide prepared from asbestos-containing waste has similar physical and chemical properties to the layered double hydroxide synthesized by traditional resource. Moreover, the adsorption capacities of the layered double hydroxide prepared from asbestos-containing waste for Congo Red and Cr(VI) are 112.3 and 29.8 mg/g, respectively, suggesting its promising application for waste water purification. In addition to that, the acid-treated derivatives of asbestos-containing waste can be used in other fields, such as adsorbent, catalyst carrier.