Advancements in textile dye removal: a critical review of layered double hydroxides and clay minerals as efficient adsorbents

The textile industry is responsible for producing large volumes of wastewater that contain a wide variety of dye compounds. This poses a significant environmental hazard and risks harming both ecosystems and living organisms. This review study explores the advancements in adsorption research for dye removal, with a particular emphasis on the development of various adsorbents. The article provides detailed insights into the toxicity and classification of dyes, different treatment techniques, and the characteristics of numerous adsorbents, with special attention to layered double hydroxides (LDH) and clay minerals. A comprehensive list of adsorbents, encompassing natural materials, agricultural by-products, industrial waste, and activated carbon, is discussed for effective removal of different dyes. Furthermore, the review extensively examines the influence of various adsorption variables, such as pH, initial dye concentration, adsorbent dosage, temperature, contact time, ionic strength, and pore volume of the adsorbent. Additionally, the application of response surface methodology for optimizing adsorption variables is elucidated. Commonly, electrostatic attraction, π-π interactions, n-π interactions, van der Waals forces, H-bonding, and pore diffusion play a major role in adsorption mechanism. The review also found that LDH can eliminate a wide range of dyes from wastewater, achieving excellent uptake capacities often exceeding 500 mg/g, with a removal efficiency of 99%. The Langmuir isotherm and pseudo-second-order kinetic equations gave the best fit to most of the adsorption data. Overall, this review serves as a valuable resource for researchers and practitioners seeking sustainable solutions to address the environmental challenges posed by textile dye contamination.

Polyvinyl Alcohol Assisted Iron-Zinc Nanocomposite for Enhanced Optimized Rapid Removal of Malachite Green Dye

Eliminating hazardous contaminants is a necessity for maintaining a healthy environment on Earth. This work used a sustainable method to create Iron-Zinc nanocomposites with polyvinyl alcohol assistance. Mentha Piperita (mint leaf) extract was used as a reductant in the green synthesis of bimetallic nanocomposites. Doping with Poly Vinyl Alcohol (PVA) caused a reduction in crystallite size and greater lattice parameters. XRD, FTIR, EDS, and SEM techniques were used to establish their surface morphology and structural characterization. The high-performance nanocomposites were used to remove malachite green (MG) dye using the ultrasonic adsorption technique. Adsorption experiments were designed by central composite design and optimized by response surface methodology. According to this study, 77.87% of the dye was removed at the optimum optimized parameters (10.0 mg L^-1 was the concentration of MG dye at a time of 8.0 min, pH 9.0, and 0.02 g of adsorbent amount) with adsorption capacity up to 92.59 mg·g^-1. The dye adsorption followed Freundlich's isotherm model and the pseudo-second-order kinetic model. Thermodynamic analysis affirmed the spontaneous nature of adsorption due to negative ΔG^o values. As a result, the suggested approach offers a framework for creating an effective and affordable technique to remove the dye from a simulated wastewater system for environmental conservation.

Regulation pore size distribution for facilitating malachite green removal on carbon foam

Malachite green (MG) is widely used as a textile dye and an aquacultural biocide, and become a serious pollution of drink water, but effectually isolating and removing it from wastewater are still a challenge. Here we report a new strategy to prepare a carbon foam with tunable pore size distribution by a one-pot lava foam process. We find that uniform micropore size is beneficial to the formation of C-OH coordination on the pore surface, increasing MG adsorption rates via H⁺ ionization. As a result, carbon foam with uniform pore size distribution demonstrates an optimum MG removal efficiency of 1812 mg g^-1 and a higher partition coefficient of 3.02 mg g^-1 μM^-1, which is twice that of carbon foams with irregular pore size distribution. The adsorption of MG onto these adsorbents was found to be an endothermic monolayer chemical adsorption process, and the Gibbs free energy of adsorption process was decreased obviously by regulating micropore size distribution. The experiment results are in good agreement with pseudo-second-order kinetic and Langmuir isotherm models. Revealed the pore size distribution was the critical factor of MG removal by carbon foam. It should be and inspiration for the design and development of highly efficiency adsorbents for dyes removal.

Application of Taguchi method and response surface methodology into the removal of malachite green and auramine-O by NaX nanozeolites

In the present study, the simultaneous removal of malachite green (MG) and auramine-O (AO) dyes from the aqueous solution by NaX nanozeolites in a batch system is investigated. Taguchi method and response surface methodology (RSM) were used to optimize and model dye removal conditions. In order to do so, the effect of various factors (dyes concentration, sonication time, ionic strength, adsorbent dosage, temperature, and pH of the solution) on the amount of dye removal was evaluated by the Taguchi method. Then, the most important factors were chosen and modeled by the RSM method so as to reach the highest percentage of dye removal. The proposed quadratic models to remove both dyes were in good accordance with the actual experimental data. The maximum removal efficiencies of MG and AO dyes in optimal operating conditions were 99.07% and 99.61%, respectively. Also, the coefficients of determination (R2) for test data were 0.9983 and 0.9988 for MG and AO dyes, respectively. The reusability of NaX nanozeolites was evaluated during the adsorption process of MG and AO. The results showed that the adsorption efficiency decreases very little up to five cycles. Moreover, NaX nanozeolites were also applied as adsorbents to remove MG and AO from environmental water samples, and more than 98.1% of both dyes were removed from the solution in optimal conditions.

Carbon-based adsorbents for fluoroquinolone removal from water and wastewater: A critical review

This review summarizes the adsorptive removal of Fluoroquinolones (FQ) from water and wastewater. The influence of different physicochemical parameters on the adsorptive removal of FQ-based compounds is detailed. Further, the mechanisms involved in the adsorption of FQ-based antibiotics on various adsorbents are succinctly described. As the first of its kind, this paper emphasizes the performance of each adsorbent for FQ-type antibiotic removal based on partition coefficients of the adsorbents that is a more sensitive parameter than adsorption capacity for comparing the performances of adsorbents under various adsorbate concentrations and heterogeneous environmental conditions. It was found that π-π electron donor-acceptor interactions, electrostatic interactions, and pore-filling were the most prominent mechanisms for FQ adsorption by carbon and clay-based adsorbents. Among all the categories of adsorbents reviewed, graphene showed the highest performance for the removal of FQ antibiotics from water and wastewater. Based on the current state of knowledge, this review fills the gap through methodolically understanding the mechanism for further improvement of FQ antibiotics adsorption performance from water and wastewater.

Sonophotocatalytic Degradation of Malachite Green by Nanocrystalline Chitosan-Ascorbic Acid@NiFe2O4 Spinel Ferrite

Statistics show that more than 700 thousand tons of dye are produced annually across the globe. Around 10–20% of this is used in industrial processes such as printing and dyeing, while about 50% of the dye produced is discharged into the environment without proper physicochemical treatment. Even trace amounts of dye in water can reduce oxygen solubility and have carcinogenic, mutagenic, and toxic effects on aquatic organisms. Therefore, before dye-containing wastewater is discharged into the environment, it must be properly treated. The present study investigates the green synthesis of nickel ferrite NiFe2O4 (NIFE) spinel magnetic nanoparticles (MNPs) via chemical coprecipitation of a solution of Ni2+/Fe3+ in the presence of a biopolymer blend of chitosan (CT) and ascorbic acid (AS). The magnetic nanomaterial was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy–energy dispersive X-ray analysis (SEM-EDX), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), differential scanning calorimetry (DSC), and vibrating-sample magnetometry (VSM). The material was further explored as a catalyst for the photocatalytic degradation of malachite green (MG) under visible light irradiation coupled with ultrasonic waves. The combination of 90 min of visible solar light irradiation with 6.35 W·mL−1 ultrasonic power at pH 8 resulted in 99% of the photocatalytic efficiency of chitosan-ascorbic acid@NIFE (CTAS@NIFE) catalyst for 70 mg·L−1 MG. The quenching of the photocatalytic efficiency from 98% to 64% in the presence of isopropyl alcohol (IPA) suggested the involvement of hydroxy (•OH) radicals in the mineralization process of MG. The high regression coefficients (R2) of 0.99 for 35, 55, and 70 mg·L−1 MG indicated the sonophotocatalysis of MG by CTAS@NIFE was best defined by a pseudo first-order kinetic model. The mechanism involves the adsorption of MG on the catalyst surface in the first step and thereby mineralization of the MG by the generated hydroxyl radicals (•OH) under the influence of visible radiation coupled with 6.34 W·mL−1 ultrasonic power. In the present study the application of photodegradation process with sonochemistry results in 99% of MG mineralization without effecting the material structure unlike happens in the case adsorption process. So, the secondary pollution (generally happens in case of adsorption) can be avoided by reusing the spent material for another application instead of disposing it. Thus, the ecofriendly synthesis protocol, ease in design of experimentation like use of solar irradiation instead of electric power lamps, reusability and high efficiency of the material suggested the study to be potentially economical for industrial development at pilot scale towards wastewater remediation.

Mechanism of sonication time on structure and adsorption properties of 3D peanut shell/graphene oxide aerogel

A 3D pretreated peanut shell-supported graphene oxide (PPS/GO) aerogel has been facilely prepared through a brief sonication + freeze-shaping technique, avoiding the traditional application of hydrothermal method which suffered from high temperature and long reaction time as well as significant loss of oxygen-containing functional groups. It was then employed to efficient norfloxacin (NOR) removal from aqueous medium. The mechanism of sonication time on the structure and adsorption properties of as-obtained PPS/GO aerogels was emphatically discussed via combining instrumental analyses, batch adsorption experiments and density functional theory (DFT) calculations. Results showed that the 3D PPS/GO aerogel with a decrease in oxygen functional groups and an increase in sp²-derived sp³ hybridization regions was observed as sonication time provided in excess, causing the worse removal efficiency towards NOR. The resulting PPS/GO(5:1) aerogel obtained at sonication of 2 min and GO loading content of 200 mg/(PPS)g exhibited the optimal NOR adsorption capacity (pH 6.2, 228.83 mg g^-1). DFT calculations further identified that the sp³-hybridized areas in PPS/GO aerogel had much lower adsorption energy (ΔE, -6.69 kcal/mol) towards NOR as compared with that of sp²-hybridized zones (-12.45 kcal/mol). In addition, multiple interactions were involved in the adsorption of NOR by 3D PPS/GO aerogel, including electrostatic attraction, H-bonding, π-π conjugation and hydrophobic effect.

Microwave-Assisted Preparation of Activated Carbon Modified by Zinc Chloride as a Packing Material for Column Separation of Saccharides

Activated carbon, an amorphous carbon material with a high specific surface area and void fraction, is widely used as an economical adsorbent in many fields. In this work, a kind of new activated carbon composite for saccharide column separation was prepared by zinc chloride impregnating and microwave heating. The structural characterizations validate the increase in porosity and the specific surface area of the activated carbon as well as the change of the activated carbon crystallite lattice. The chemical characterizations validate the increase in the number of oxygen-containing functional groups and structural bonding of zinc with the activated carbon surface. Compared with the blank control, the surface Zn element improves the adsorption selectivity of the activated carbon to the target saccharides. Under the special mechanism of microwaves, the pores created by expansion from the inside to the outside facilitate the free flow of the mobile phase. The eight saccharides can be separated by the columns packed with the activated carbon impregnated with 40% and 70% zinc chloride.

Green fabrication of ZnO nanoparticles using Eucalyptus spp. leaves extract and their application in wastewater remediation

The present study explored removal of carcinogenic cationic and anionic dyes from aqueous medium using green fabricated zinc oxide nanoparticles (ZnO-NPs). The ZnO-NPs were synthesized employing biogenic green reduction and precipitation approach. The characterization of ZnO NPs was done using various techniques such as FESEM, XRD, BET, TGA, HRTEM, EDX, and FTIR. All experiments were conducted in batch mode. Maximum removal was achieved at pH 6.0 and pH 8.0 for Congo Red (CR) and Malachite Green (MG) dyes respectively. Dye adsorption process showed better fit with Langmuir and Temkin isotherm models for CR dye and MG dye respectively. Maximum adsorption capacity of ZnO NPs was 48.3 mg/g for CR dye and 169.5 mg/g for MG dye. The dye adsorption followed pseudo-second order model and values of thermodynamic parameters confirmed that the adsorption process was spontaneous and favourable. Reusability efficiency of the nanoparticle was explored using ethanol and water and based on results it was inferred that ZnO-NPs can be reused for dye removal. Effect of salinity on the removal of CR and MG dyes was also explored and found that presence of salinity in aqueous medium have adverse impact on the dye removal efficiency of ZnO-NPs.

Decolorization of crystal violet from aqueous solutions by a novel adsorbent chitosan/nanodiopside using response surface methodology and artificial neural network-genetic algorithm

A novel adsorbent of chitosan/nanodiopside nanocomposite (CS-NDIO) was synthesized as a green composite for the removal of crystal violet (CV) and characterized by techniques like XRD, FT-IR, BET, and FESEM analysis. The influence of parameters like molar ratios of CS to NDIO, initial pH of the solution, dosage of adsorbent, initial concentration of CV and contact time was investigated and evaluated by central composite design (CCD; 5 levels and 4 factors). Also, Hybrid model of (ANN) model with genetic algorithm (GA) optimization was applied to the experimental data get through CCD. The optimized molar ratio of CS-NDIO was found: 20/80. Optimal parameter choice for maximum CV adsorption process using CCD and ANN-GA were as follows: pH = 7.50 and 7.499, adsorbent mass: 0.0077 and 0.0077 g, CV concentration: 20.000 and 20.002 mg/L, and contact time: 25.00 and 25.00 min, respectively. The evaluation adsorption equilibrium and kinetic data were fitted with the Langmuir monolayer isotherm model (q_max: 104.66 mg g^-1 and R²: 0.9937) and pseudo-second order kinetics mechanism (R²: 0.9978). Thermodynamic parameters (R²: 0.9180, ΔH°: -74.93 kJ mol^-1, ΔG°: -12.89 kJ mol^-1, and ΔS°: 0.93 kJ mol^-1 K^-1) were calculated and indicating adsorption to be an exothermic and spontaneous process.

Trace determination of safranin O dye using ultrasound assisted dispersive solid-phase micro extraction: Artificial neural network-genetic algorithm and response surface methodology

In this study, ultrasound assisted dispersive solid-phase micro extraction combined with spectrophotometry (USA-DSPME-UV) method based on activated carbon modified with Fe2O3 nanoparticles (Fe2O3-NPs-AC) was developed for pre-concentration and determination of safranin O (SO). It is known that the efficiency of USA-DSPME-UV method may be affected by pH, amount of adsorbent, ultrasound time and eluent volume and the extent and magnitude of their contribution on response (in term of main and interaction part) was studied by using central composite design (CCD) and artificial neural network-genetic algorithms (ANN-GA). Accordingly by adjustment of experimental conditions suggested by ANN-GA at pH 6.5, 1.1mg of adsorbent, 10min ultrasound and 150μL of eluent volume led to achievement of best operation performance like low LOD (6.3ngmL(-1)) and LOQ (17.5ngmL(-1)) in the range of 25-3500ngmL(-1). In following stage, the SO content in real water and wastewater samples with recoveries between 93.27-99.41% with RSD lower than 3% was successfully determined.

Experimental design and modeling of ultrasound assisted simultaneous adsorption of cationic dyes onto ZnS: Mn-NPs-AC from binary mixture

The manganese impregnated zinc sulfide nanoparticles deposited on activated carbon (ZnS: Mn-NPs-AC) which fully was synthesized and characterized successfully applied for simultaneous removal of malachite green and methylene blue in binary situation. The effects of variables such as pH (2.0-10.0), sonication time (1-5min), adsorbent mass (0.005-0.025g) and MB and MG concentration (4-20mgL(-1)) on their removal efficiency was studied dy central composite design (CCD) to correlate dyes removal percentage to above mention variables that guides amongst the maximum influence was seen by changing the sonication time and adsorbent mass. Sonication time, adsorbent mass and pH in despite of dyes concentrations has positive relation with removal percentage. Multiple regression analysis of the experimental results is associated with 3-D response surface and contour plots that guide setting condition at pH of 7.0, 3min sonication time, 0.025g Mn: ZnS-NPs-AC and 15mgL(-1) of MB and MG lead to achievement of removal efficiencies of 99.87% and 98.56% for MG and MB, respectively. The pseudo-second-order model as best choice efficiency describe the dyes adsorption behavior, while MG and MB maximum adsorption capacity according to Langmuir was 202.43 and 191.57mgg(-1).

Synthesis of magnetic γ-Fe2O3-based nanomaterial for ultrasonic assisted dyes adsorption: Modeling and optimization

γ-Fe2O3 nanoparticles were synthesized and loaded on activated carbon. The prepared nanomaterial was characterized by field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The γ-Fe2O3 nanoparticle-loaded activated carbon (γ-Fe2O3-NPs-AC) was used as novel adsorbent for the ultrasonic-assisted removal of methylene blue (MB) and malachite green (MG). Response surface methodology and artificial neural network were applied to model and optimize the adsorption of the MB and MG in their individual and binary solutions followed by the investigation on adsorption isotherm and kinetics. The individual effects of parameters such as pH, mass of adsorbent, ultrasonication time as well as MB and MG concentrations in addition to the effects of their possible interactions on the adsorption process were investigated. The numerical optimization revealed that the optimum adsorption (>99.5% for each dye) is obtained at 0.02g, 15mgL(-1), 4min and 7.0 corresponding to the adsorbent mass, each dye concentration, sonication time and pH, respectively. The Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms were studied. The Langmuir was found to be most applicable isotherm which predicted maximum monolayer adsorption capacities of 195.55 and 207.04mgg(-1) for the adsorption of MB and MG, respectively. The pseudo-second order model was found to be applicable for the adsorption kinetics. Blank experiments (without any adsorbent) were run to investigate the possible degradation of the dyes studied in presence of ultrasonication. No dyes degradation was observed.