Environmental application of Saccharum munja biomass-derived hybrid composite for the simultaneous removal of cationic and anionic dyes and remediation of dye polluted water: A step towards pilot-scale studies

Fabricating pine needles derived spherical nanocellulose with polyaniline and montmorillonite clay for simultaneous removal of cationic and anionic dyes from binary mixtures

Herein, pine needles derived spherical nanocellulose (SNC) was combined with aniline to form SNC-polyaniline (SNC-PANI), followed by modification with montmorillonite (MMT) to form SNC-PANI-MMT composite. The as-synthesized materials were characterized by FTIR, XRD, XPS, TGA, FESEM, and EDS and evaluated for the simultaneous adsorption of cationic and anionic dyes, malachite green (MG), and Congo red (CR) from MG-CR mixture, and fuchsin basic (FB) and methyl orange (MO) from FB-MO mixture. Non-linear kinetics of adsorption showed the anionic dyes, CR and MO to follow pseudo-first order kinetics with 91.30 % and 85.50 % removal, respectively, while the cationic dyes, MG and FB followed Elovich model with 95.10 % and 83.10 % removal, respectively. Non-linear isotherm analysis showed all the dyes to follow Langmuir isotherm with maximum adsorption capacity of 282.394 and 298.420 mgg-1 (120 min, 25 °C, 7.0 pH) for MG and CR, respectively, whereas the same for FB and MO were 194.126 and 185.757 mgg-1, respectively. The dyes were adsorbed through electrostatic, π-π, ion-dipole interactions, and hydrogen-bonding. The SNC-PANI-MMT showed regeneration and reusability upto nine cycles with high cumulative adsorption capacity. Thus, the composite has appreciable cost-effectiveness, high sustainability, environmental friendliness, and holistic characteristics for the treatment of real dyes-polluted wastewater.

Simultaneous removal of cationic and anionic dyes from a complex mixture using a novel composite hydrogel based on pine needles, chitosan, and gelatin

Following a holistic sustainable approach, we fabricated a biocomposite from pine needles (PNs), with two biopolymers, chitosan (CS) and gelatin (GEL). The biocomposite was used as an effective, regenerable, and reusable adsorbent for the removal of cationic and anionic dyes from their mixture. The cationic dyes chosen were malachite green, methylene blue, and crystal violet; and the anionic dyes were methyl orange and Congo red. The PNs were etherified followed by composite formation with glutaraldehyde-mediated crosslinked network of CS/GEL. Synthesis of composite, i.e. etherified PNs/CS/GEL was confirmed by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Energy-dispersive X-ray (EDX) analysis, and surface charge analysis. The adsorption kinetics studied by different kinetic models, such as pseudo-first-order, pseudo-second-order, and Elovich, followed the Elovich model. Among the three adsorption isotherms (Langmuir, Freundlich, and Temkin) studied, the adsorption followed Langmuir isotherm with maximum adsorption capacity of 307.871 mgg-1 for the mixture of dyes. The reusability studies affirmed the ease of regeneration of the hydrogel for use in multiple cycles. The reported adsorbent is green, low-cost, eco-friendly, and recyclable with a high potential to remove cationic and anionic dyes from their mixture and the real dye-contaminated wastewater.

Molecular simulation-based insights into dye pollutant adsorption: A perspective review

Growing concerns about environmental pollution have highlighted the need for efficient and sustainable methods to remove dye contamination from various ecosystems. In this context, computational methods such as molecular dynamics (MD), Monte Carlo (MC) simulations, quantum mechanics (QM) calculations, and machine learning (ML) methods are powerful tools used to study and predict the adsorption processes of dyes on various adsorbents. These methods provide detailed insights into the molecular interactions and mechanisms involved, which can be crucial for designing efficient adsorption systems. MD simulations, detailing molecular arrangements, predict dyes' adsorption behaviour and interaction energies with adsorbents. They simulate the entire adsorption process, including surface diffusion, solvent layer penetration, and physisorption. QM calculations, especially density functional theory (DFT), determine molecular structures and reactivity descriptors, aiding in understanding adsorption mechanisms. They identify stable adsorption configurations and interactions like hydrogen bonding and electrostatic forces. MC simulations predict equilibrium properties and adsorption energies by sampling molecular configurations. ML methods have proven highly effective in predicting and optimizing dye adsorption processes. These models offer significant advantages over traditional methods, including higher accuracy and the ability to handle complex datasets. These methods optimize adsorption conditions, clarify adsorbent functionalization roles, and predict dye removal efficiency under various conditions. This research explores MD, MC, QM, and ML approaches to connect molecular interactions with macroscopic adsorption phenomena. Probing these techniques provides insights into the dynamics and energetics of dye pollutants on adsorption surfaces. The findings will aid in developing and optimizing new materials for dye removal. This review has significant implications for environmental remediation, offering a comprehensive understanding of adsorption at various scales. Merging microscopic data with macroscopic observations enhances knowledge of dye pollutant adsorption, laying the groundwork for efficient, sustainable removal technologies. Addressing the growing challenges of ecosystem protection, this study contributes to a cleaner, more sustainable future.

Eco-friendly engineering of micro composite-based hydroxyapatite bio crystal and polyaniline for high removal of OG dye from wastewater: Adsorption mechanism and RSM@BBD optimization

The presence of harmful substances such as dyes in water systems poses a direct threat to the quality of people's lives and other organisms living in the ecosystem. Orange G (OG) is considered a hazardous dye. The existing paper attempts to evaluate a low-cost adsorbent for the effective removal of OG dye. The developed adsorbent Polyaniline@Hydroxyapatite extracted from Cilus Gilberti fish Scale (PANI@FHAP) was elaborated through the application of the in situ chemical polymerization method to incorporate PANI on the surface of naturally extracted hydroxyapatite FHAP. The good synthesis of PANI@FHAP was evaluated through multiple techniques including X-ray diffraction (XRD), Scanning electron microscopy coupled with energy dispersive X-ray spectrometry (SEM/EDS), Fourier Transforms Infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) coupled with thermal differential analysis (DTA) analysis. The results reveal a highly ordered disposition of PANI chains on FHAP, resulting in a well-coated FHAP in the PANI matrix. Furthermore, the presence of functional groups on the surface of PANI such as amine (-NH2) and imine (=NH) groups would facilitate the removal of OG dye from contaminated water. The adsorption of OG onto PANI@FHAP was conducted in batch mode and optimized through response surface methodology coupled with box-Behnken design (RSM/BBD) to investigate the effect of time, adsorbent dose, and initial concentration. The outcomes proved that OG adsorption follows a quadratic model (R2 = 0.989). The kinetic study revealed that the adsorption of OG fits the pseudo-second-order model. On the other hand, the isotherm study declared that the Freundlich model is best suited to the description of OG adsorption. For thermodynamic study, the adsorption of OG is spontaneous in nature and exothermic. Furthermore, the regeneration-reusability study indicates that PANI@FHAP could be regenerated and reused up to five successive cycles. Based on the FTIR spectrum of PANI@FHAP after OG adsorption, the mechanism governing OG adsorption is predominantly driven by π-π interaction, electrostatic interaction, and hydrogen bonding interactions. The obtained results suppose that PANI@FHAP adsorbent can be a competitive material in large-scale applications.

Valorization of castor seed shell waste as lead adsorbent by treatment with hot phosphoric acid: Optimization and evaluation of adsorption properties

Lead is used in many industries such as refining, mining, battery manufacturing, smelting. Releases of lead from these industries is one of the major public health concerns due to widespread persistence in the environment and its resulting poisoning character. In this work, the castor seed shell (CSS) waste was exploited for preparing a beneficial bio-adsorbent for removal of Pb(II) ions from water. The raw CSS was modified with H3PO4 at different acid concentrations, impregnation ratios, activation times, and temperatures. An optimum adsorption capacity was observed for CSS modified with 2 M acid, 5 mL g-1 solid to liquid ratio, treated at 95 °C for 160 min. Exploiting acid modification, the SEM, XRD, and FTIR analyses show some alterations in functional groups and the surface morphology of the biomass. The impacts of physiochemical variables (initial lead ions concentration, pH, adsorbent dose and adsorption time) on the lead removal percentage were investigated, using response surface methodology (RSM). Maximum removal of 72.26% for raw CSS and 97.62% for modified CSS were obtained at an initial lead concentration (50 mg L-1), pH (5.7), adsorption time (123 min) and adsorbent dosage (1.1 g/100 mL). Isothermal and kinetics models were fitted to adsorption equilibrium data and kinetics data for the modified CSS and the adsorption system was evaluated thermodynamically and from the energy point of view. Isothermal scrutinization indicated the mono-layer nature of adsorption, and the kinetics experimental outcomes best fitted with the pseudo-second-order, implying that the interaction of lead ions and hot acid-treated CSS was the rate-controlling phenomenon of process. Overall, results illustrated that the hot acid-treated biomass-based adsorbent can be considered as an alternative bio-adsorbent for removing lead from water media.

Upcycling of sugar refining mud solid waste as a novel adsorbent for removing methylene blue and Congo red from wastewater

The feasibility of utilizing the mud solid waste (MSW) produced during the carbonation process of sugar refining as a cost-effective and environmentally friendly alternative for the water removal of methylene blue (MB) and Congo red (CR), being highly utilized organic dyes representing cationic and anionic species, respectively is presented. Prior to its use, the MSW was dried at 110 °C for 24 h and sieved through a 100-mesh screen. The chief constituent of the MSW utilized was CaCO3, with a point of zero charge (PZC) found at pH 8.4 and 7.96 m2 g-1 total surface area. XRD and FTIR data indicate the presence of interactions between the dyes and the MSW surface, indicating effective adsorption. Different variables, such as initial dye concentration, MSW weight, solution pH, contact time, and temperature, were all examined to determine the optimal dye removal conditions. A central composite design (CCD) approach based on response surface methodology (RSM) modeling was utilized to identify statistically significant parameters for MB and CR adsorption capacities onto the MSW adsorbent. The removal equilibrium was typically reached in 120 minutes, with the greatest removal efficiency of CR taking place at pH 2 and 328 K, while the highest MB removal efficiency was obtained at pH 12 and 296 K. Kinetic studies suggest the adsorption of both dyes on the MSW follow pseudo-second-order rates, as evident through the high correlations obtained. Linearized and non-linearized Langmuir models showed strong correlations indicating maximum adsorption capacities of 86.6 and 72.3 mg g-1 for MB and CR, respectively. High regeneration and reusability potential of the MSW was demonstrated especially for the adsorption of CR, where the removal efficiency was nearly constant throughout five adsorption cycles, ranging from 93 to 91%, while the reduction in the removal for MB was much more significantly impacted, diminishing from 95 to 79% after the five cycles.

Revealing the interface chemistry of polyaniline grafted biomass via statistical modeling of multi-component dye systems: optimization, kinetics, thermodynamics, and adsorption mechanism

The growing need to examine the adsorption capabilities of innovative materials in real-world water samples has encouraged a shift from single to multicomponent adsorption systems. In this study, a novel composite, PANI-g-SM was synthesized by covalently grafting a lignocellulosic biomass, Saccharum munja (SM) with polyaniline (PANI). The as-synthesized composite was investigated for the simultaneous adsorption of cationic (Methylene Blue (MB); Crystal Violet (CV)) and anionic dyes (Reactive Red 35 (RR); Fast Green FCF (FG)) from four single components and two binary systems, MB + RR and CV + FG. Further, the effect and interaction of pH (2-11), dosage (0.01-0.04 g/10 mL), and initial concentration (0.0313 to 0.1563 mmol/L) on the elimination of dyes by PANI-g-SM were studied through a novel design of Box-Behnken of Response Surface Methodology (RSM) technique which was found to be highly useful for revealing the chemistry of interfaces in multi-component systems. The extended Langmuir model for the binary system indicated the presence of synergism, as result the maximum monolayer adsorption capacity increased by 44.44%, 645.83%, 67.88%, and 441.07% for MB, RR, CV, and FG dye, respectively. Further, the adsorption process mainly followed a pseudo-second-order kinetic model, and the thermodynamic studies revealed the exothermic nature of adsorption for RR and FG dye while endothermic for MB and CV dye, respectively with Δ G varying from - 1.68 to - 6.12 kJ/mol indicating the spontaneity of the process. Importantly, the efficacy of the composite was evaluated for the treatment of textile industry effluent highlighting its potential as an adsorbent for wastewater treatment.

Recent insights into mechanism of modified bio-adsorbents for the remediation of environmental pollutants

Rapid industrialization has exacerbated the hazard to health and the environment. Wide spectrums of contaminants pose numerous risks, necessitating their disposal and treatment. There is a need for further remediation methods since pollutant residues cannot be entirely eradicated by traditional treatment techniques. Bio-adsorbents are gaining popularity due to their eco-friendly approach, broad applicability, and improved functional and surface characteristics. Adsorbents that have been modified have improved qualities that aid in their adsorptive nature. Adsorption, ion exchange, chelation, surface precipitation, microbial uptake, physical entrapment, biodegradation, redox reactions, and electrostatic interactions are some of the processes that participate in the removal mechanism of biosorbents. These processes can vary depending on the particular biosorbent and the type of pollutants being targeted. The systematic review focuses on the many modification approaches used to remove environmental contaminants. Different modification or activation strategies can be used depending on the type of bio-adsorbent and pollutant to be remediated. Physical activation procedures such as ultrasonication and pyrolysis are more commonly used to modify bio-adsorbents. Ultrasonication process improves the adsorption efficiency by 15-25%. Acid and alkali modified procedures are the most effective chemical activation strategies for adsorbent modification for pollution removal. Chemical modification increases the removal to around 95-99%. The biological technique involving microbial culture is an emerging field that needs to be investigated further for pollutant removal. A short evaluation of modified adsorbents with multi-pollutant adsorption capability that have been better eliminated throughout the adsorption process has been provided.

Removal of cationic dye pollutants from wastewater with HS loaded semi-IPN composites: kinetic and thermodynamic studies

In this study, methylene blue (MB) pollutant in water was removed using produced hazelnut shell loaded semi-interpenetrating polymer networks (HS loaded semi-IPN) adsorbent. The physical and chemical characterizations of the adsorbents were investigated using TGA, DSC, FT-IR, BET, FE-SEM, and EDX. Experimental parameters such as temperature, swelling, dye concentration, contact time, pH solution, and adsorbent dosage for MB adsorption were thoroughly investigated. It was determined that the HS loaded semi-IPN adsorbent removed 92.1% of MB dye. Subsequently, the adsorption properties between the adsorbent and dye were investigated in detail using several different kinetic, isotherm, and thermodynamic models. As a result of the obtained data, the interaction between adsorbent and dye molecules is discussed. Moreover, studies on the industrial usability of the adsorbent have been carried out, and it has been observed that the adsorbent can be employed even after four cycles.

Dependency of Crystal Violet Dye Removal Behaviors onto Mesoporous V2O5-g-C3N4 Constructed by Simplistic Ultrasonic Method

This research examined the production of a V2O5-g-C3N4 nanocomposite to remove organic dyes from wastewater. To generate the V2O5-g-C3N4 nanocomposite, the sonication method was applied. The testing of V2O5-g-C3N4 with various dyes (basic fuchsin (BF), malachite green (MG), crystal violet (CV), Congo red (CR), and methyl orange (MO)) revealed that the nanocomposite has a high adsorption ability towards BF, MG, CV, and CR dyes in comparison with MO dye. It was established that the modification of pH influenced the removal of CV by the V2O5-g-C3N4 nanocomposite and that under optimal operating conditions, efficiency of 664.65 mg g−1 could be attained. The best models for CV adsorption onto the V2O5-g-C3N4 nanocomposite were found to be those based on pseudo-second-order adsorption kinetics and the Langmuir isotherm. According to the FTIR analysis results, the CV adsorption mechanism was connected to π–π interactions and the hydrogen bond.

Remediation of water tainted with noxious hexavalent chromium using cetylpyridinium-modified bagasse biomass: adsorption and regeneration studies

Herein, cetylpyridinium-modified bagasse (SB-CPC) biomass was synthesized and applied for removal of noxious Cr(VI) ions from aqueous matrix. Batch mode analyses were conducted, and the results showed that SB-CPC adsorbent has a maximum uptake capacity (q_m) of 70.5 ± 3.2 mg g^-1 at 303 K. The adsorption isotherms and kinetics for elimination of Cr(VI) by SB-CPC were better fitted by Langmuir model and pseudo-second-order model, respectively. The occurrence of pseudo-second-order kinetic could be mainly influenced by the intra-particle diffusion mass transfer. Electrostatic attraction was the dominant underlying reaction mechanism followed by pore filing effect (minor). Thermodynamic study affirms the endothermic behavior and occurrence of physical adsorption process. SB-CPC adsorbent had exhibited an outstanding desorption-regeneration performance using NaOH solution; accordingly, it can practically be applied for remediation of wastewater tainted with Cr(VI) ions.