Modelling of dye adsorption from aqueous solution on polyaniline/carboxymethyl cellulose/TiO2 nanocomposites

Synthesis of biodegradable sodium alginate-based carbon dot-nanomagnetic composite (SA-FOCD) for enhanced water remediation using ANN modelling, RSM optimization, and economic analysis

This study involves the synthesis of a magnetic‑sodium alginate bio-composite embedded with carbon dots, designed to eliminate pollutants like dyes and metal ions and tackle environmental issues. The modified particles are effectively incorporated into the biopolymers for improved adsorption and regeneration performance using an economically viable and environmentally sustainable process. The composite's surface morphology and chemical structure have been extensively characterized through various analytical techniques. It has been found that CD-modified nanoparticles demonstrate good dispersion, abundance in functional groups, and excellent adsorption performance. The adsorption process variables have been optimized using Response Surface Methodology (RSM), resulting in a maximum adsorption capacity of 232.44 mg/g achieved under optimal conditions. An Artificial Neural Network (ANN) model with a topology of 3-5-5-1 is constructed to predict the adsorption capacity of composite, exhibiting superior predictive performance. The statistical physical model was also performed to understand the adsorption mechanism and orientation of dye molecules attached to the surface of the composite. The adsorption capacity using statistical physical method was found to be 467.57 mg/g. The composite exhibits good adsorption and regeneration performance in the column adsorption study. Furthermore, a detailed cost analysis of the synthesized composite was performed, ensuring its economic viability in real-world applications.

Biogenic synthesis of dopamine/carboxymethyl cellulose/TiO2 nanoparticles using Psidium guajava leaf extract with enhanced antimicrobial and anticancer activities

The green synthesis of metal oxide nanoparticles (NPs) has garnered considerable attention from researchers due to its utilization of eco-friendly solvents during synthesis and cost-effective approaches. This study focuses on the synthesis of titanium oxide (TiO2) and dopamine (DA) carboxymethyl cellulose (CMC)-doped TiO2 (DA/CMC/TiO2) NP using Psidium guajava leaf extract, while also investigating the structural, optical, and morphological and biocidal potential of the prepared NPs. Significantly larger zones of inhibition were observed for DA/CMC/TiO2 NPs compared to TiO2 against various pathogens. Moreover, the MTT assay was carried out to evaluate the anticancer activity of the prepared samples against MG-63 cells, and the results revealed that DA/CMC/TiO2 NPs exhibited significantly higher level of anticancer activity compared to TiO2. The experimental results demonstrated that DA/CMC/TiO2 NPs exhibited enhanced anticancer activity in a dose-dependent manner when compared to TiO2 NPs.

Removal of cationic dyes from aqueous solution using polyacrylic acid modified hemp stem

Water pollution caused by dyes is a pressing environmental challenge due to their persistence and difficulty in degradation. Herein, an anionic adsorbent (HS-PAANa) was synthesized by grafting polyacrylic acid (PAA) onto the agricultural waste-hemp stem (HS). The obtained HS-PAANa adsorbent exhibited rapid adsorption kinetics, high adsorption capacity, and a favorable preference for cationic dyes, such as methylene blue (MB) and crystal violet (CV). The experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm, demonstrating the efficiency of HS-PAANa in dye removal. Notably, the optimal adsorption capacities of HS-PAANa for MB and CV were found to be 1296.65 mg/g and 1451.43 mg/g, respectively. In the cationic/anionic dyes (MB/MO) binary systems, HS-PAANa exhibited enhanced selective adsorption of cationic dyes (MB), indicating its potential for targeted removal of specific dyes from mixed solutions. Moreover, HS-PAANa adsorption shows an excellent recyclability, after five cycles, HS-PAANa still maintained MB and CV removal rates of 93.85% and 95.08%, respectively. Therefore, the bioadsorbent HS-PAANa exhibits high potential as a highly efficient adsorbent for the effective treatment of cationic pollutants in wastewater.

Comprehensive Evaluation of Polyaniline-Doped Lignosulfonate in Adsorbing Dye and Heavy Metal Ions

Lignosulfonate/polyaniline (LS/PANI) nanocomposite adsorbent materials were prepared by the chemical polymerization of lignosulfonate with an aniline monomer as a dopant and structure-directing agent, and the adsorption behavior of dyes as well as heavy metal ions was investigated. LS/PANI composites were used as dye adsorbents for the removal of different cationic dyes (malachite green, methylene blue, and crystal violet). The adsorption behavior of LS/PANI composites as dye adsorbents for malachite green was investigated by examining the effects of the adsorbent dosage, solution pH, initial concentration of dye, adsorption time, and temperature on the adsorption properties of this dye. The following conclusions were obtained. The optimum adsorption conditions for the removal of malachite green dye when LS/PANI composites were used as malachite green dye adsorbents were as follows: an adsorbent dosage of 20 mg, an initial concentration of the dye of 250 mg/L, an adsorption time of 300 min, and a temperature of 358 K. The LS/PANI composite adsorbed malachite green dye in accordance with the Langmuir adsorption model and pseudo-second-order kinetic model, which belongs to chemisorption-based monomolecular adsorption, and the equilibrium adsorption amount was 245.75 mg/g. In particular, the adsorption of heavy metal ion Pb2+ was investigated, and the removal performance was also favorable for Pb2+.

Fabrication of cationic cellulose nanofibrils/sodium alginate beads for Congo red removal

Congo red is hard to remove from dye wastewater due to its structure stability and high chemical oxygen demand. In this study, cationic cellulose nanofibrils (CCNF) prepared from herb residues was physically crosslinked with sodium alginate (SA) in the presence of calcium ions, and the obtained CCNF/SA beads were used to adsorb Congo red. Results showed that CCNF/SA beads with porous internal structure were beneficial to adsorption. The maximum adsorption capacity of Congo red could reach to 518.4 mg/g, which was superior to most cellulose-based adsorption materials. Furthermore, the equilibrium adsorption isotherms and XPS analysis indicated the adsorption for Congo red was a physical process, and hydrogen bond and electrostatic adsorption were proposed as dominant adsorption mechanism. In addition, the Congo red removal efficiency of the beads was still higher than 70% after three cycles. Therefore, this high efficiency and green beads have great potential as adsorbents for anionic dyes removal.

Adsorption of hexavalent chromium, Rhodamine B and Congo red simultaneously in aquatic by zeolitic imidazolate framework coupling carbon nanotubes

Zeolitic imidazolate framework/carbon nanotube (ZIF-67/CNTs) was prepared by precipitation method. ZIF-67/CNTs maintained the characteristics of large specific surface area and high porosity of ZIFs, showing stable cubic structure. The adsorption capacities of ZIF-67/CNTs for Cong red (CR), Rhodamine B (RhB) and Cr(VI) were 36.82 mg/g, 1421.29 mg/g and 716.67 mg/g under the conditions of 2:1, 3:1 and 1:3 masses of ZIF-67 and CNTs, respectively. The optimum adsorption temperature of CR, RhB and Cr(VI) were 30 °C, and the removal rates at the adsorption equilibrium were 81.22%, 72.87% and 48.35%. The adsorption kinetic model of the three adsorbents on ZIF-67/CNTs was consistent with the quasi-second order reaction model, and the adsorption isotherms were more consistent with adsorption law of Langmuir. The adsorption mechanism for Cr(VI) was mainly electrostatic interaction, and the adsorption mechanism for azo dyes was the combination of physical and chemical adsorption. This study would provide theoretical basis for further developing metal organic framework (MOF) materials for environmental applications.

The Defects, Physicochemical Properties, and Surface Charge of MIL-88A (Al) Crystal Were Regulated for Highly Efficient Removal of Anionic Dyes: Preparation, Characterization, and Adsorption Mechanism

In this paper, the physicochemical properties, surface charge, and crystal defects of MIL-88A (Al) were controlled by adjusting the ratio of metal ligands and temperature in the synthetic system without the addition of surfactants. The adsorption properties of different crystals for Congo red (CR) were studied. Among them, MIL-88A (Al)-130 and MIL-88A (Al)-d have the best adsorption properties. The maximum adsorption capacities are 600.8 and 1167 mg · g^-1, respectively. Compared with MIL-88A (Al)-130, the adsorption performance of MIL-88A (Al)-d was increased by 94.2%, and the adsorption rate was increased by about 4 times. It can be seen that increasing the proportion of metal ligands within a certain range will improve the adsorption capacity. The structure and morphology of the adsorbent were characterized by XRD, FTIR, SEM, EDS, TGA, BET, and zeta potential. The effects of time, temperature, pH, initial solution concentration, and dosage on CR adsorption properties were systematically discussed. The pseudo-second-order kinetic model and Langmuir isothermal model can well describe the adsorption process, which indicates that the adsorption process is a single-layer chemisorption occurring on a uniform surface. According to thermodynamics, this adsorption is an endothermic process. The mechanism of CR removal is proposed as the electrostatic attraction, hydrogen bond, metal coordination effect, π-π conjugation, crystal defect, and pore-filling effect. In addition, MIL-88A (Al)-d has good repeatability, indicating that it is a good material for treating anionic dye wastewater.

Facile synthesis of CoFe2O4@MIL-53(Al) nanocomposite for fast dye removal: Adsorption models, optimization and recyclability

The global occurrence of textile dyes pollution has recently emerged, posing a serious threat to ecological systems. To abate dye contamination, we here developed a novel magnetic porous CoFe₂O₄@MIL-53(Al) nanocomposite by incorporating magnetic CoFe₂O₄ nanoparticles with MIL-53(Al) metal-organic framework. This nanocomposite possessed a surface area of 197.144 m² g^-1 and a pore volume of 0.413 cm³ g^-1. The effect of contact time (5-120 min), concentration (5-50 mg L^-1), dosage (0.1-1.0 g L^-1), and pH (2-10) on Congo red adsorption was clarified. CoFe₂O₄@MIL-53(Al) could remove 95.85% of Cong red dye from water with an accelerated kinetic rate of 0.6544 min^-1 within 10 min. The kinetic and isotherm models showed the predominance of Bangham and Temkin. According to Langmuir, the maximum uptake capacities of CoFe₂O₄@MIL-53(Al), CoFe₂O₄, and MIL-53(Al) adsorbents were 43.768, 17.982, and 15.295 mg g^-1, respectively. CoFe₂O₄@MIL-53(Al) was selected to optimize Cong red treatment using Box-Behnken experimental design. The outcomes showed that CoFe₂O₄@MIL-53(Al) achieved the highest experimental uptake capacity of 35.919 mg g^-1 at concentration (29.966 mg L^-1), time (14.926 min), and dosage (0.486 g L^-1). CoFe₂O₄@MIL-53(Al) could treat dye mixture (methylene blue, methyl orange, Congo red, malachite green, and crystal violet) with an outstanding removal efficiency of 81.24% for 30 min, and could be reused up to five cycles. Therefore, novel recyclable and stable CoFe₂O₄@MIL-53(Al) is recommended to integrate well with real dye treatments systems.

Treatment of electroplating industry wastewater: a review on the various techniques

Water pollution by recalcitrant compounds is an increasingly important problem due to the continuous introduction of new chemicals into the environment. Choosing appropriate measures and developing successful strategies for eliminating hazardous wastewater contaminants from industrial processes is currently a primary goal. Electroplating industry wastewater involves highly toxic cyanide (CN), heavy metal ions, oils and greases, organic solvents, and the complicated composition of effluents and may also contain biological oxygen demand (BOD), chemical oxygen demand (COD), SS, DS, TS, and turbidity. The availability of these metal ions in electroplating industry wastewater makes the water so toxic and corrosive. Because these heavy metals are harmful to living things, they must be removed to prevent them from being absorbed by plants, animals, and humans. As a result, exposure to electroplating wastewater can induce necrosis and nephritis in humans and lung cancer, digestive system cancer, anemia, hepatitis, and maxillary sinus cancer with prolonged exposure. For the safe discharge of electroplating industry effluents, appropriate wastewater treatment has to be provided. This article examines and assesses new approaches such as coagulation and flocculation, chemical precipitation, ion exchange, membrane filtration, adsorption, electrochemical treatment, and advanced oxidation process (AOP) for treating the electroplating industry wastewater. On the other hand, these physicochemical approaches have significant drawbacks, including a high initial investment and operating cost due to costly chemical reagents, the production of metal complexes sludge that needs additional treatment, and a long recovery process. At the same time, advanced techniques such as electrochemical treatment can remove various kinds of organic and inorganic contaminants such as BOD, COD, and heavy metals. The electrochemical treatment process has several advantages over traditional technologies, including complete removal of persistent organic pollutants, environmental friendliness, ease of integration with other conventional technologies, less sludge production, high separation, and shorter residence time. The effectiveness of the electrochemical treatment process depends on various parameters, including pH, electrode material, operation time, electrode gap, and current density. This review mainly emphasizes the removal of heavy metals and another pollutant such as CN from electroplating discharge. This paper will be helpful in the selection of efficient techniques for treatment based on the quantity and characteristics of the effluent produced.

A Facile Review on the Sorption of Heavy Metals and Dyes Using Bionanocomposites

Presently, hazardous metal and dye removal from wastewater is one of the major areas of research focus. For the elimination of these contaminants, many approaches have been devised and applied. However, the accomplishment of various water treatment processes has largely depended on the medium utilized and the associated problem with the leaching of harmful compounds into the water process with most commercial and chemically manufactured materials for water treatment processes. Hence, this study is aimed at reviewing existing studies on the sorption of heavy metals (HMs) and dyes using bionanocomposites (BNCs). The key focus of this review is on the development of eco-friendly, effective, and appropriate nanoadsorbents that could accomplish superior and enhanced contaminant sequestration using BNCs owing to their biodegradability, biocompatible, environmentally friendly, and not posing as secondary waste to the environment. The sorption of most pollutants was observed to be pH, sorbent dosage, and initial contaminant concentration-dependent, with most contaminants’ elimination taking place in the pH range of 2-10. The sorption process of HMs and dyes to various BNCs was superlatively depicted utilizing the Langmuir (LNR) and Freundlich (FL) as well as the pseudo-second-order (PSO) models, suggestive of the sorption process of a monolayer and multilayer and the chemisorption process, the rate-limiting stage in surface sorption. The established sorption capacities for the reviewed sorption process for various contaminants ranged from 1.47 to 740.97 mg/g. Future prospective for the treatment and remediation of contaminated water using BNCs was also discussed.

Highly enhanced dye adsorption of MoO3 nanoplates fabricated by hydrothermal-calcination approach in presence of chitosan and thiourea

Water pollution by organic dyes poses great challenge to the environment and living organism. Hence effective removal of organic dyes by cost effective methods have received significant attention in recent years. Herein, we report the complete removal of organic dyes (rhodamine B), methylene blue) and eosin yellow) from water via effective adsorption by MoO₃ catalyst. Hydrothermally synthesised MoO₂ (1) and amorphous MoS_x (2) using ammonium molybdate without and with thiourea exhibited low dye adsorption. In contrast, crystalline micro/nanoplates of MoO₃ (3 and 4) obtained from calcination of 1 and 2 showed highly enhanced dye adsorption. Particularly 4 showed higher dye adsorption compared to 3. UV-Visible absorption studies confirmed complete removal of organic dyes upon stirring with MoO₃ catalyst. Dye removal studies further revealed that cationic dyes are adsorbed faster than anionic dye that could be attributed to the surface charge of MoO₃. Interestingly, the adsorbed dyes were not released from MoO₃ for more than 50 days. The exhausted MoO₃ catalyst can be recovered by annealing at 400 °C. MoO₃ catalyst has also been used as packing materials in dropper column and demonstrated effective removal of dyes by passing through dyes separately as well as mixture.

A Review of the Modeling of Adsorption of Organic and Inorganic Pollutants from Water Using Artificial Neural Networks

The application of artificial neural networks on adsorption modeling has significantly increased during the last decades. These artificial intelligence models have been utilized to correlate and predict kinetics, isotherms, and breakthrough curves of a wide spectrum of adsorbents and adsorbates in the context of water purification. Artificial neural networks allow to overcome some drawbacks of traditional adsorption models especially in terms of providing better predictions at different operating conditions. However, these surrogate models have been applied mainly in adsorption systems with only one pollutant thus indicating the importance of extending their application for the prediction and simulation of adsorption systems with several adsorbates (i.e., multicomponent adsorption). This review analyzes and describes the data modeling of adsorption of organic and inorganic pollutants from water with artificial neural networks. The main developments and contributions on this topic have been discussed considering the results of a detailed search and interpretation of more than 250 papers published on Web of Science ® database. Therefore, a general overview of the training methods, input and output data, and numerical performance of artificial neural networks and related models utilized for adsorption data simulation is provided in this document. Some remarks for the reliable application and implementation of artificial neural networks on the adsorption modeling are also discussed. Overall, the studies on adsorption modeling with artificial neural networks have focused mainly on the analysis of batch processes (87%) in comparison to dynamic systems (13%) like packed bed columns. Multicomponent adsorption has not been extensively analyzed with artificial neural network models where this literature review indicated that 87% of references published on this topic covered adsorption systems with only one adsorbate. Results reported in several studies indicated that this artificial intelligence tool has a significant potential to develop reliable models for multicomponent adsorption systems where antagonistic, synergistic, and noninteraction adsorption behaviors can occur simultaneously. The development of reliable artificial neural networks for the modeling of multicomponent adsorption in batch and dynamic systems is fundamental to improve the process engineering in water treatment and purification.

Preparation of Magnetic Composite Polyaniline/Fe3O4−Hydrotalcite and Performance in Removal of Methyl Orange

Magnetic composite fabricated from polyaniline and Fe3O4-hydrotalcite (Pan/MHT) was successfully applicated for removal of methyl orange (MO) from wastewater. The structure and properties of Pan/MHT were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction, vibrating sample magnetometer, and Brunauer-Emmett-Teller adsorption isotherm. Adsorption kinetic results indicated that the adsorption process followed pseudosecond-order kinetic model ( $R^2=0.999$ ), MO adsorption onto Pan/MHT was well described by Freundlich isotherm ( $R^2=0.994$ ), and the MO adsorption capacity of 2 Pan/MHT obtained the highest with $Q_e=156.25\text{mg}/\text{g}$ . Batch adsorption experiments were carried out using magnetic composite with the effects of initial MO concentration, solution pH, and adsorbent dosage. The results revealed that the magnetic Pan/MHT exhibited efficient adsorption of MO in the aqueous solution as a result of the affinity for organic dyes, microporous structure, and suitable surface area for adsorption (15,460 m2/g). The superparamagnetic behavior of Pan/MHT (with $H_c=18.56\text{Oe}$ , $M_s=23.38\times {10}^{-3}\text{emu}/\text{g}$ , and $M_r=0.91\times {10}^{-3}\text{emu}/\text{g}$ ) helps that it could be separated from the solution and performs as an economical and alternative adsorbent to removal and degrade azo dye from wastewater. Pan/MHT was also investigated to reuse after desorption of MO in 0.1 M HCl, and the results show that 2 Pan/MHT can be reused for 4 cycles with $Q_e=79.66\text{mg}/\text{g}.$

Optimized synthesis of lignin sulfonate nanoparticles by solvent shifting method and their application for adsorptive removal of dye pollutant

Synthesis of value added products from wastes is of importance from different perspectives. Wood and paper industry produces tons of wastewaters that contains lignin. In this paper, we report a new approach, called solvent-shifting method, to synthesize lignin sulfonate nanoparticles (LS-NPs). The effective parameters on size of LS-NPs were carefully tuned and the size of LS-NPs was minimized by response surface methodology. The results suggested that LS-NPs with size of 53 nm can be synthesized at low lignin sulfonate concentration (0.28 g/mL), moderate surfactant concentration (0.32 g/mL) but relatively high anti-solvent content (92 mL of ethanol for 40 mL of the aqueous phase). The as-synthesized LS-NPs were characterized by different analytical techniques, where presence of various negatively charged functional groups on surface of LS-NPs was conformed. To investigate the potential of LS-NPs for adsorptive removal of pollutant molecules, basic red 2 (known as Safranin-O) was used as a model pollutant dye. The results suggested that the maximum removal occurs at alkaline pH, where there is strong electrostatic interactions between LS-NPs and cationic Safranin-O molecules. The adsorption capacity was 85.14 mg/gr, where the isotherm data was best described by Redlich-Peterson isotherm model. The kinetic data also revealed that the adsorption is very fast in the first 20 min, where there is three diffusional steps to complete the adsorption in 90 min. The results of this study could open up new window to the field of value-added products to synthesize waste-driven nanomaterials for environmental applications.

Nanocellulose-Based Materials for Water Treatment: Adsorption, Photocatalytic Degradation, Disinfection, Antifouling, and Nanofiltration

Nanocelluloses are promising bio-nano-materials for use as water treatment materials in environmental protection and remediation. Over the past decades, they have been integrated via novel nanoengineering approaches for water treatment processes. This review aims at giving an overview of nanocellulose requirements concerning emerging nanotechnologies of waster treatments and purification, i.e., adsorption, absorption, flocculation, photocatalytic degradation, disinfection, antifouling, ultrafiltration, nanofiltration, and reverse osmosis. Firstly, the nanocellulose synthesis methods (mechanical, physical, chemical, and biological), unique properties (sizes, geometries, and surface chemistry) were presented and their use for capturing and removal of wastewater pollutants was explained. Secondly, different chemical modification approaches surface functionalization (with functional groups, polymers, and nanoparticles) for enhancing the surface chemistry of the nanocellulose for enabling the effective removal of specific pollutants (suspended particles, microorganisms, hazardous metals ions, organic dyes, drugs, pesticides fertilizers, and oils) were highlighted. Thirdly, new fabrication approaches (solution casting, thermal treatment, electrospinning, 3D printing) that integrated nanocelluloses (spherical nanoparticles, nanowhiskers, nanofibers) to produce water treatment materials (individual composite nanoparticles, hydrogels, aerogels, sponges, membranes, and nanopapers) were covered. Finally, the major challenges and future perspectives concerning the applications of nanocellulose based materials in water treatment and purification were highlighted.

Selective capture of toxic anionic dyes of a novel prepared DMDAAC-grafted chitosan/genipin/cellulose hydrogel beads with antibacterial activity

Novel eco-friendly and green dimethyldiallylammonium chloride (DMDAAC) grafted chitosan/genipin/cellulose hydrogel beads (CCBG-g-PDMDAAC), were fabricated as selective adsorbents for anionic dyes. The physical and chemical structural changes of the prepared hydrogels were evaluated by FTIR, XRD, SEM and TG-DSC analysis. Results showed CCBG-g-PDMDAAC efficiently and selectively adsorb anionic dyes (Reactive Red 195-RR195 and Methyl orange-MO) from mixture of dye solutions. Endowed chitosan-based hydrogels the advantage of acid insolubility and good adsorption. RR195 and MO adsorption process were described better with pseudo-second-order kinetic model and Langmuir isotherm model with a maximum adsorption capacity of 1333.52 and 190.48 mg/g, respectively, indicating that monolayer chemisorption controlled the sorption process. Moreover, the hydrogels exhibited nice reusability and against S. aureus and E. coli. The hydrogels are promising for the potential application in wastewater treatment and antibacterial simultaneously.

Effective removal of levofloxacin drug and Cr(VI) from water by a composed nanobiosorbent of vanadium pentoxide@chitosan@MOFs

Wastewaters is generally polluted with various inorganic and organic contaminants which require effective multipurpose purification technology. In this respect, a novel V₂O₅@Ch/Cu-TMA nanobiosorbent was constructed via encapsulation of nanoscale metal organic frameworks (Cu-TMA) into vanadium pentoxide-imbedded-chitosan matrix to comprehensively investigate its efficiency in removal of levofloxacin drug (LEVO) (e.g., organic pollutant) and chromium (VI) (e.g., inorganic pollutant) from water. Both LEVO drug and Cr(VI) adsorptions were correlated to pseudo-second order (R² = 1) and Langmuir isotherm (R² = 0.9924 for LEVO and R² = 0.9815 for Cr(VI)). Adsorption of Cr(VI) was confirmed to be spontaneous and endothermic reactions, while LEVO was found to proceed via spontaneous and exothermic reactions based on the thermodynamic parameters. The emerged V₂O₅@Ch/Cu-TMA is regarded as an excellent nanobiosorbent for removal of inorganic contaminant as Cr(VI) from all natural water samples (tap, sea and wastewater) with percentages range 92.43%-96.95% and organic contaminant as LEVO drug from tap and wastewater (91.99%-97.20%).

Intelligent modeling and experimental study on methylene blue adsorption by sodium alginate-kaolin beads

As tighter regulations on color in discharges to water bodies are more widely implemented worldwide, the demand for reliable inexpensive technologies for dye removal grows. In this study, the removal of the basic dye, methylene blue, by adsorption onto low-cost sodium alginate-kaolin beads was investigated to determine the effect of operating parameters (initial dye concentration, contact time, pH, adsorbent dosage, temperature, agitation speed) on dye removal efficiency. The composite beads and individual components were characterized by a number of analytical techniques. Three models were developed to describe the adsorption as a function of the operating parameters using regression analysis, and two powerful intelligent modeling techniques, genetic programming and artificial neural network (ANN). The ANN model is best in predicting dye removal efficiency with R² = 0.97 and RMSE = 3.59. The developed model can be used as a useful tool to optimize treatment processes using the promising adsorbent, to eliminate basic dyes from aqueous solutions. Adsorption followed a pseudo-second order kinetics and was best described by the Freundlich isotherm. Encapsulating the kaolin powder in sodium alginate resulted in removal efficiency of 99.56% and a maximum adsorption capacity of 188.7 mg.g^-1, a more than fourfold increase over kaolin alone.

Photodegradation of organic water pollutants under visible light using anatase F, N co-doped TiO2/SiO2 nanocomposite: Semi-pilot plant experiment and density functional theory calculations

Visible-light driven photocatalysts are of great importance in wastewater treatment. In this work, fluorine and nitrogen co-doped titanium dioxide/silica nanocomposite (F-N-TiO₂/SiO₂) was synthetized using a sol-gel approach. The as-developed nanocomposite was well characterized using different techniques. In particular, an anatase structure with high surface area (345.69 m²/g) and a band gap of 2.97 eV were observed for the as-synthesized nanocomposite, which makes it a potential candidate for photocatalytic applications under visible light. A systematic density functional theory calculation was performed to get more insight into the effect of dopant atoms on the band gap of TiO₂ nanoparticles. To enhance the reusability of the photocatalyst in semi-pilot scale, the as-developed nanocomposite was immobilized onto the glass beads by coupling dip-coating and heat attachment methods. A semi-pilot scale custom-designed fixed-bed photoreactor was used to evaluate the photocatalytic performance of the as-developed nanocomposite under both visible and solar irradiations. A mixture of three azo dyes (i.e., basic red 29, basic blue 41 and basic yellow 51) was used as the model industrial wastewater. The analysis of the wastewater showed that the complete removal of the pollutants under visible light and sunlight can occurred at pH of 3 and flow rate of 280 mL/min. The durability results demonstrated the successful degradation of the pollutants for five cycles. The results of this study show how careful controlling the operational parameters as well as using a highly photocatalytic nanomaterial can lead to successful decontamination of organic water pollutants. This approach might open up new windows to the future applications of photocatalytic nanomaterials for wastewater treatment.

Surface modified polythiophene/Al2O3 and polyaniline/Al2O3 nanocomposites using poly(vinyl alcohol) for the removal of heavy metal ions from water: kinetics, thermodynamic and isotherm studies

In this study, polythiophene/Al₂O₃ (PTh/Al₂O₃) and polyaniline/Al₂O₃ (PAn/Al₂O₃) nanocomposites in the presence of poly(vinyl alcohol) (PVA) as the surfactant were synthesized via in situ chemical oxidative polymerization method in aqueous medium. The synthesized nanocomposites were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Results indicated that the Al₂O₃ and poly(vinyl alcohol) influenced the properties of synthesized nanocomposites. The aim of this research was to investigate the sorption characteristics of polythiophene and polyaniline nanocomposites for the removal of heavy metal cations including Pb(II), Zn(II) and Cd(II) from aqueous solution. The factors that affected the adsorption equilibrium as well as the removal efficiency of the nanoadsorbents, i.e., contact time, metal ion concentration, pH and adsorption conditions were investigated in detail. From the kinetic results, it was concluded that the pseudo-second-order kinetic model was found to be the best at describing the adsorption process for Pb(II), Zn(II) and Cd(II) on PTh-PVA/Al₂O₃ and PAn-PVA/Al₂O₃. In addition, thermodynamic analysis suggests the endothermic and spontaneous nature of the present adsorption process with increased entropy on PTh-PVA/Al₂O₃ and PAn-PVA/Al₂O₃. The results suggest polythiophene, polyaniline and their nanocomposites have great potential to be used as efficient absorbent for the removal of heavy metal ions from water.

Ultrasound-assisted synthesis of MIL-88(Fe) coordinated to carboxymethyl cellulose fibers: A safe carrier for highly sustained release of tetracycline

For stopping long-time harmful bacterial infection, designing a drug carrier with a highly prolonged release profile is a promising approach that is of interest to different biomedical areas. The subject of this work is to synthesis a novel carrier system through coordination of MIL-88(Fe) to carboxymethyl cellulose (CMC) for enhancing interaction between drug and carrier. We established an ultrasound-assisted synthetic method for in situ synthesis of MIL-88(Fe) in the presence of CMC resulting in CMC/MIL-88(Fe) composite. The CMC/MIL-88(Fe) was loaded with a high amount of Tetracycline (TC) by immersion of carrier to the TC aqueous solution. The release profile in the simulated physiological conditions, pH 7.4, revealed a low initial burst release followed by a sustained and prolonged release over 384 h. The in vitro cytotoxicity of CMC/MIL-88(Fe) against Human skin fibroblast (HFF-1) cells was calculated by MTT assay and showed a good cytocompatibility. The antibacterial activity was found for TC-loaded CMC/MIL-88(Fe) toward both E. coli and S. aureus with MIC 64 mg·ml^-1.

Integration with MoO3 microrods as precursors for hierarchical polyaniline microtubes and composites for anionic dye removal in water treatment

PANI microtubes were well constructed with MoO₃ microrods as a sacrificing template, and exhibited excellent performance for dye removal. Moreover, the PANI microtubes can be a good support to synthesize multifunctional PANI-based composites.

Carboxymethyl cellulose improved adsorption capacity of polypyrrole/CMC composite nanoparticles for removal of reactive dyes: Experimental optimization and DFT calculation

In this study, polypyrrole/carboxymethyl cellulose nanocomposite particles (PPy/CMC NPs) were synthesized and applied for removal of reactive red 56 (RR56)and reactive blue 160 (RB160) as highly toxic dyes. The amount of CMC was found significantly effective on the surface adsorption efficiency. Different optimization methods including the genetic programming, response surface methodology, and artificial neural network (ANN) were used to optimize the effect of different parameters including pH, adsorption time, initial dye concentration and adsorbent dose. The maximum adsorption of RR56 and RB160 were found under the following optimum conditions: pH of 4 and 5, adsorption time of 55 min and 52 min for RR56 and RB160, respectively, initial dye concentration of 100 mg/L and adsorbent dose of 0.09 g for both dyes. were obtained for RR56 and RB160, respectively. Also, the results indicated that ANN method could predict the experimental adsorption data with higher accuracy than other methods. The analysis of ANN results indicated that the adsorbent dose is the main factor in RR56 removal, followed by time, pH and initial concentration, respectively. However, initial concentration mostly determines the RB160 removal process. The isotherm data for both dyes followed the Langmuir isotherm model with a maximum adsorption capacity of 104.9 mg/g and 120.7 mg/g for RR56 and RB160, respectively. In addition, thermodynamic studies indicated the endothermic adsorption process for both studied dyes. Moreover, DFT calculations were carried out to obtain more insight into the interactions between the dyes and adsorbent. The results showed that the hydrogen bondings and Van der Waals interactions are dominant forces between the two studied dyes and PPy/CMC composite. Furthermore, the interaction energies calculated by DFT confirmed the experimental adsorption data, where PPy/CMC resulted in higher removal of both dyes compared to PPy. The developed nanocomposite showed considerable reusability up to 3 cylces of the batch adsorption process.

Adsorption kinetic models: Physical meanings, applications, and solving methods

Adsorption technology has been widely applied in water and wastewater treatment, due to its low cost and high efficiency. The adsorption kinetic models have been used to evaluate the performance of the adsorbent and to investigate the adsorption mass transfer mechanisms. However, the physical meanings and the solving methods of the kinetic models have not been well established. The proper interpretation of the physical meanings and the standard solving methods for the adsorption kinetic models are very important for the applications of the kinetic models. This paper mainly focused on the physical meanings, applications, as well as the solving methods of 16 adsorption kinetic models. Firstly, the mathematical derivations, physical meanings and applications of the adsorption reaction models, the empirical models, the diffusion models, and the models for adsorption onto active sites were analyzed and discussed in detail. Secondly, the model validity evaluation equations were summarized based on literature. Thirdly, a convenient user interface (UI) for solving the kinetic models was developed based on Excel software and provided in supplementary information, which is helpful for readers to simulate the adsorption kinetic process.

Elaboration of novel polyaniline@Almond shell biocomposite for effective removal of hexavalent chromium ions and Orange G dye from aqueous solutions

A novel polyaniline@Almond shell (PANI@AS) biocomposite was synthesized via facile in situ chemical polymerization method. The as-synthesized adsorbent was characterized using various analytical techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM), and potentiometric titration. A batch adsorption system was applied with the aim of investigating as-synthesized adsorbent ability to remove Cr(VI) ions and Orange G (OG) textile dye from aqueous solutions. Obtained results revealed that adsorption process was strongly depended upon the physicochemical parameters. The adsorption of Cr(VI) and OG dye onto PANI@AS was better described by the pseudo second-order-kinetic model and followed the Freundlich isotherm model. The maximum uptakes were 335.25 for Cr(VI) and 190.98 mg g^-1 for OG dye. We further evaluated that PANI@AS biocomposite could be regenerated easily with NaOH solution and efficiently reused for Cr(VI) and OG dye removal from aqueous media. Thus, these results indicated the potential practical application of PANI@AS biocomposite for wastewater treatment.

Nano-engineered Adsorbent for the Removal of Dyes from Water: A Review

Background:

The huge quantity of wastewater, containing poisonous and hazardous dyes, is released by various industries which pollute water in direct and indirect ways. Most of the dyes are a dangerous class of water contaminants which have affected the environment drastically. Some dyes such as congo red, rhodamine B, methylene blue, methyl violet, and crystal violet are a serious threat to human beings.

Remediation Method:

Numerous methods are available for the removal of dyes from water. Adsorption, being a superior and eco-friendly technique, has advantage of eliminating organic dyes because of the availability of materials as adsorbents. The inexpensive nanomaterials are a more attractive choice for remediation of various dyes due to their unique properties and offer an adequate pathway to adsorb any organic dye from water to overcome its hazardous effects on human health.

Results:

In this review, we have discussed the latest literature related to various types of synthesis, characterization and uses as adsorbent for highly adsorptive removal capacity of nanoparticles for organic dyes.

Conclusion:

Adsorption technology provides an attractive pathway for further research and improvement in more efficient nanoparticles, with higher adsorption capacity, for numerous dyes to eliminate the dyes discharged from various industries and thus reduce the contamination of water. Therefore, nanocomposites may contribute to future prospective water treatment process.

Recent Developments of the Solution-Processable and Highly Conductive Polyaniline Composites for Optical and Electrochemical Applications

Solution-processable conducting polymers (CPs) are an effective means for producing thin-film electrodes with tunable thickness, and excellent electrical, electrochemical, and optical properties. Especially, solution-processable polyaniline (PANI) composites have drawn a great deal of interest due to of their ease of film-forming, high conductivity up to 10³ S/cm, excellent redox behaviors, processability, and scalability. In this review, basic principles, fabrication methods, and applications of solution-processable PANI composites will be discussed. In addition, recent researches on the PANI-based electrodes for solar cells (SCs), electrochromic (EC) windows, thermoelectric (TE) materials, supercapacitors, sensors, antennas, electromagnetic interference (EMI) shielding, organic field-effect transistors (OFETs), and anti-corrosion coatings will be discussed. The presented examples in this review will offer new insights in the design and fabrication of high-performance electrodes from the PANI composite solutions for the development of thin-film electrodes for state-of-art applications.

Experimental studies and neural network modeling of the removal of trichloroethylene vapor in a biofilter

In this study, bamboo carrier based lab scale compost biofilter was evaluated to treat synthetic waste air containing trichloroethylene (TCE) under continuous operation mode. The effect of inlet TCE concentration and gas flow rate and its removal was investigated. Maximum TCE removal efficiency was found to be 89% under optimum conditions of inlet 0.986 g/m³ TCE concentration corresponding to a loading rate of 43 g/m³ h and 0.042 m³/h gas flow rate at empty bed residence time (EBRT) of 2 min. For the first time, Artificial Neural Network (ANN) was applied to predict the performance of the compost biofilter in terms of TCE removal. The ANN model used a three layer feed forward based Levenberg-Marquardt algorithm, and its topology consisted of 3-25-1 as the optimum number for the three layers (input, hidden and output). An excellent match between the experimental and ANN predicted the value of TCE removal was obtained with a coefficient of determination (R²) value greater than 0.99 during the model training, validation, testing and overall. Furthermore, statistical analysis of the ANN model performance mediated its prediction accuracy of the bioreactor to treat TCE contaminated systems.