Removal of cationic dye from coloured water by adsorption onto hematite-humic acid composite: Experimental and theoretical studies

Bio-inspired magnetic chitosan/Iron oxide macromolecules for multiple anionic dyes adsorption from aqueous media

Organic anionic dyes are major water pollutants due to their low degradability caused by complex aromatic structures. Not only do they exert toxic, mutagenic, teratogenic, tumorigenic, and genotoxic effects, but they also decrease fertility and cause irritation to the skin and respiratory system in humans. This long-term toxicity has detrimental effects on aquatic organisms and their surroundings, resulting in an imbalanced ecosystem. In this study, a Cs@Fe3O4 magnetic biosorbent was synthesised to uptake three anionic dyes and characterised for FTIR, BET/BJH, XRD, TGA, VSM, and FESEM analyses. The biosorbent average surface area was confirmed to be 52.6524 m2/g, with average pore sizes of 7.3606 nm and 6.9823 nm for adsorption-desorption processes, respectively. Batch adsorption studies pH values, contact times, temperature, initial dye concentrations, and adsorbent dosages were examined. Several isotherm and kinetic models were studied to determine the adsorption mechanism. The adsorption data of these dyes at equilibrium was observed to match Langmuir's isotherm and pseudo-second-order kinetic models. The thermodynamic study revealed that the adsorption process for these dyes was an exothermic reaction. Maximum adsorption capacities for congo red, methyl orange, and metanil yellow were 117.77 mg/g, 137.77 mg/g, and 155.57 mg/g, respectively. The reusability of recovered Cs@Fe3O4 after dye adsorption was evaluated up to five continuous adsorption-desorption cycles for its possible industrial applications.

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.

Nanostructured Mn@NiO composite for addressing multi-pollutant challenges in petroleum-contaminated water

Efficient catalysts play a pivotal role in advancing eco-friendly water treatment strategies, particularly in the removal of diverse organic contaminants found in water-petroleum sources. This study addresses the multifaceted challenges posed by contaminants, encompassing a spectrum of heavy metals such as As, Cd, Cr, Mn, Mo, Ni, Pb, Sb, Se, and Zn alongside pollutants like oily water (OIW), total suspended solids (TSS), chemical oxygen demand (COD), dyes, and pharmaceuticals, posing threats to both aquatic and terrestrial ecosystems. Herein, we present the synthesis of biogenically derived Mn@NiO nanocomposite (NC) photocatalysts, a sustainable methodology employing an aqueous Rosmarinus officinalis L. extract, yielding particles with a size of 36.7 nm. The catalyst demonstrates exceptional efficacy in removing heavy metals, achieving rates exceeding 99-100% within 30 min, alongside notable removal efficiencies for OIW (98%), TSS (87%), and COD (98%). Furthermore, our photodegradation experiments showed remarkable efficiencies, with 94% degradation for Rose Bengal (RB) and 96% for methylene blue (MB) within 120 min. The degradation kinetics adhere to pseudo-first-order behavior, with rate constants of 0.0227 min-1 for RB and 0.0370 min-1 for MB. Additionally, the NC exhibits significant antibiotic degradation rates of 97% for cephalexin (CEX) and 96% for amoxicillin (AMOX). The enhanced photocatalytic performance is attributed to the synergistic interplay between the Mn and NiO nanostructures, augmenting responsiveness to sunlight while mitigating electron-hole pair recombination. Notably, the catalyst demonstrates outstanding stability and reusability across multiple cycles, maintaining its stable nanostructure without compromise.

Optimization of glass scrap recovery and reuse in road construction for promising physicochemical stabilization

Waste glass is hugely present in Morocco, and can be recycled for many geotechnical purposes, including road construction. In contrast, earthworks often produce significant amounts of clay waste that lack the necessary technical criteria for use as barriers. The present work aimed to study the influence of the addition of glass waste on the evolution of the mechanical characteristics of clays stabilized with crushed glass (particles less than 63 μm). The work consists of carrying out CBR, Proctor, and shear tests on natural clay taken as a reference and mixtures (clay-crushed glass) at different percentages. Results showed that the addition of glass to clay decreases the swelling and compaction indices along with modifying the intrinsic characteristics of the clay.

Coagulation process for the removal of color and turbidity from wet coffee processing industry wastewater using bio-coagulant: Optimization through central composite design

The growing problem of industrial pollution in developing countries, especially Ethiopia, has sparked serious issues about the quality of the water, particularly when it comes to the effluent from wet coffee processing industries. In response, this study investigates the potential of utilizing natural coagulants, Acanthus sennii C., Moringa stenopetala B., and Aloe vera L., either individually or in combination, for the treatment of coffee effluent. Methodologically, the study systematically varies operational parameters, including coagulant dose, pH levels, stirring speed, and stirring time, to evaluate their impact on coagulation efficiency. Experimental data undergo statistical analysis, employing ANOVA, while computational optimization techniques are employed using Design Expert software to determine optimal conditions. Notably, the blended form of the three coagulants emerges as particularly promising, yielding optimal conditions of 0.750 g/L coagulant dosage, pH 8.76, agitation speed of 80.73 rpm, and agitation time of 19.23 min. Under these optimized conditions, the blended coagulant achieves remarkable removal efficiencies, approximately 99.99% for color and 98.7% for turbidity. These findings underscore the efficiency of natural coagulants, particularly in blended form, for sustainable wastewater treatment in wet coffee processing.

Adsorption of Methylene Blue Dye and Analysis of Two Clays: A Study of Kinetics, Thermodynamics, and Modeling with DFT, MD, and MC Simulations

The purpose of this research was to learn more about the primary and secondary properties of Moroccan natural clay in an effort to better investigate innovative adsorbents and gain access to an ideal adsorption system. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy analysis (SEM-EDX) and X-ray fluorescence were employed for identification. SEM revealed clay grains, including tiny particles and unevenly shaped sticks. First- and second-order rate laws, representing two distinct kinetic models, were applied in the kinetic approach. Adsorption of dye MB onto natural clay was studied, and the results agreed with the 2 s order model. The significant correlation coefficients support the inference that the adsorption process was governed by the Langmuir model. Subsequent DFT analyses demonstrated that the methylene blue dye's HOMO and LUMO surfaces are dispersed across most of the dye's components, pointing to a strong interaction with the clay. To determine how the dye might be adsorbed onto the clay, we employed quantum descriptors to locate its most nucleophilic and electrophilic centers. Endothermic reactions are evident during the MB adsorption process on clay, as indicated by the positive values of ΔH0 and ΔS0 (70.49 kJ mol-1of RC and 84.19 kJ mol-1 of OC and 10.45 J mol-1 K-1 of RC and 12.68 mol-1 K-1 of OC, respectively). Additionally dye molecules on the adsorbent exhibit a higher order of distribution than in the solution, indicating that the adsorption process is spontaneous.

Promising adsorbent for dye detoxification: Exploring the potential of chitosan sodium carboxymethylcellulose silk fibroin aerogel

The main goal of this study is to create a CS-CMC-SF aerogel consisting of chitosan sodium carboxymethylcellulose and silk fibroin. The aerogel is designed to remove types of dyes from water while also being environmentally friendly. This innovative adsorbent has been optimized for extracting both cationic and anionic dyes from solutions. It incorporates chitosan sodium carboxymethylcellulose and silk filament fibers to enhance its strength. Experimental data illustrates that the CS-CMC-SF aerogel possesses remarkable adsorption capabilities - 5461.77 mg/g for Congo Red (CR), 2392.83 mg/g for Malachite Green (MG), and 1262.20 mg/g for Crystal Violet (CV). A kinetic study aligns with the pseudo-second-order kinetic model suggesting predominant chemisorption phenomena occur during adsorption process. Isotherm analysis further identifies multilayered adsorption occurring on irregularly shaped surfaces of the aerogel while thermodynamic assessments validate exothermic and spontaneous characteristics inherent in its absorption mechanism. Several analytical methods such as SEM, FT-IR, XRD, and XPS were employed to examine physicochemical attributes tied to this unique material design conceptually; identifying mechanisms including pore filling, π-π interactions, ion exchange activity, electrostatic connections along with hydrogen bonding inducing overall superior performance output. Furthermore substantial soil biodegradability alongside compostable features associated with our proposed CS-CMC-SF aerogels established it's potential suitability within applications demanding sustainable options thereby validating its underlying ecological credibility.

Synthesis of hydroxyapatite/polyethylene glycol 6000 composites by novel dissolution/precipitation method: optimization of the adsorption process using a factorial design: DFT and molecular dynamic

In this work, we presented a synthesis of a composite based on HAp and PEG 6000 using a new method of synthesis dissolution precipitation to be applied for application of wastewater purification from toxic metal ions. Multiple characterization methods were used to analyze the morphology and the structure of the well-prepared compounds including FT-IR, Raman, XRD, XPS, TGA and SEM were used to conduct a composite analysis. The adsorption effectiveness of this analysis towards Pb2+ and various other hazardous metal ions found in sewage was assessed. Batch experiments were conducted to optimize the various operational parameters including adsorbent dose, temperature, pH, contact time, and initial concentration. The Langmuir isotherm was used to fit the data, and it predicted monolayer adsorption with a maximum capacity of 67 mg g-1 for HAP PEG600 and 60 mg g-1 for HAp. A pseudo-second-order equation fits the adsorption process well (0.961-0.971). The thermodynamic data support the spontaneous metal bonding to the composite receptor sites. Theoretical calculations showed that the interaction strength is very strong and gets stronger when the PEG6000 is deprotonated. The results presented here are supported by evidence acquired from experiments. Theoretical computation using Monte Carlo (MC) and Molecular Dynamic (MD) simulation models showed excellent affinity of prepared foams for the model ion Pb2+ with highly negative adsorption energy values indicating vigorous interactions of Pb2+ with the adsorbate surfaces.

Application of Taguchi method, response surface methodology, DFT calculation and molecular dynamics simulation into the removal of orange G and crystal violet by treated biomass

In this work, the efficiency of the treated plant Carpobrotus edulis (TPCE) as an effective biosorbent for removing the orange G (OG) and crystal violet (CV) dyes from aqueous solution was investigated. TPCE was characterized by FT-IR, Ss, pHz and SEM-EDX. The influence of parameters such as bioadsorbent dose, contact time, initial concentration, temperature and pH was tested using Taguchi experimental design (TED) with L8 orthogonal array (five parameters in two levels). The initial concentration, bioadsorbent dose and contact time are the main parameters for the removal of CV and OG dyes, while the effects of pH and temperature are minimal. The maximum removal efficiency of dyes under optimal operating conditions was 97.93 % and 92.68 %, respectively. which at the optimal conditions of 3 g/L, pH 10, 20 mg/L, 35 °C, 5 min and 15 g/L, pH 4, 20 mg/L, 35 °C, 60 min for CV and OG dyes, respectively. The results of response surface methodology (RSM) and analysis of variance (ANOVA) showed that the initial concentration Ci of CV dye was the most significant factor in the adsorption efficiency with a contribution of 51.56 %. On the other hand, the OG bioadsorbent dose is the most important factor in adsorption efficiency with a percentage contribution of 56.41 %. The Density Functional Tight Binding (DFTB) method shows that dyes strongly bind the adsorbent surface. Monte Carlo and molecular dynamics simulations show significant interactions between dye and adsorbent surface. The reusability of biomaterial indicated that the adsorption performance dropped very slightly up to five cycles.

Adsorptive exclusion of crystal violet dye using barium encapsulated alginate/carbon composites: characterization and adsorption modeling studies

The present study is devoted to the removal of crystal violet dye using the synthesized barium alginate/carbon composites abbreviated as BA (barium alginate), BAAC (barium alginate/activated carbon), BASC (barium alginate/starch carbon), and BASSC (barium alginate/starch carbon modified with CTAB). The adsorptive removal of crystal violet as a function of contact time, pH of solution, composite dose, initial dye concentration, and temperature was studied. The uptake of crystal violet (CV) dye for the composites was recorded in the range of 36 mg g-1 to 50 mg g-1 at pH 8.03 ± 0.03 for an equilibrium time of 120 min. The adsorption kinetics and isotherms in compliance with the CV sorption onto BA/carbon composites corroborated the utmost fit of pseudo-second-order and Freundlich isotherm models, respectively. The recycling process was achieved using the barium alginate-treated bead carbons for different initial CV dye concentrations of 10-30 mg L-1 with a scope of zero disposal. The practicability of BA/carbon composites in a groundwater sample spiked with 30 mg L-1 of CV was successfully achieved with a removal efficiency of about 65-74%. Characterization studies for the composites using FTIR, SEM (with EDS), XRD, TGA, and BET were carried out and discussed in the paper.

An efficient and adsorption of methylene blue dye on a natural clay surface: modeling and equilibrium studies

The present research work revolves around the evaluation of the elimination of the cationic dye methylene blue (MB) from an aqueous solution by the exploitation of natural clay (TMG) from South-East Morocco. Several physicochemical techniques were used to characterize our TMG adsorbate, namely, X-ray diffraction, Fourier transform infrared absorption spectroscopy, differential thermal analysis, thermal gravimetric analysis, and zero charge point (pHpzc). The morphological properties and elemental composition of our material were identified using scanning electron microscopy coupled with an energy-dispersive X-ray spectrometer. The batch technique was used under different operating conditions to produce quantitative adsorption, namely, the amount of adsorbent, dye concentration, contact time, pH, and solution temperature. The maximum adsorption capacity of MB on TMG was 81.185 mg g^-1 for a concentration of 100 mg L^-1 MB at pH_initial = 6.43 (no initial adjustment of the pH-value was performed), temperature 293 K, and 1 g L^-1 adsorbent. The adsorption data were examined by Langmuir, Freundlich, and Temkin isotherms. The Langmuir isotherm provides the best correlation with the experimental data, and the pseudo-second-order kinetic model is more appropriate for the adsorption of the MB dye. The thermodynamic study of MB adsorption indicates that the process is physical, endothermic, and spontaneous. The Box-Behnken method was applied to identify the optimal conditions for MB removal in the design of batch experiments. The parameters examined result in >99% removal. The TMG material's regeneration cycles and low cost ($0.393 per gram) show that it is both environmentally friendly and very effective for dye removal in the various textile sectors.

Comparison of magnetite, hematite and goethite amendment and capping in control of phosphorus release from sediment

The characteristics and mechanism of phosphate adsorption onto magnetite, hematite and goethite were comparatively studied, and the effects of magnetite, hematite and goethite amendment and capping on endogenous phosphorus (P) liberation from sediment into overlying water (OW) were comparatively investigated. The adsorption of phosphate onto magnetite, hematite and goethite mainly obeyed the inner-sphere complexation mechanism, and the phosphate adsorption capacity decreased in the order of magnetite > goethite > hematite. The magnetite, hematite and goethite amendment all can decrease the risk of endogenous Prelease into OW under anoxic conditions, and the inactivation of diffusion gradients in thin films-labile P in sediment made a great contribution to the restraint of endogenous P release into OW by the magnetite, hematite and goethite amendment. The efficiency of endogenous P release restraint by the iron oxide addition decreased in the order of magnetite > goethite > hematite. The magnetite, hematite and goethite capping all can be effective for the suppression of endogenous P release from sediment into OW under anoxic conditions, and most of P immobilized by the magnetite, hematite and goethite capping layers is relatively or very stable. The results obtained from this work suggest that magnetite is more suitably used a capping/amendment material to prevent P release from sediment than hematite and goethite, and magnetite capping is a promising approach for hindering sedimentary P release into OW.

Adsorptive removal of pharmaceutically active compounds from multicomponent system using Azadirachta indica induced zinc oxide nanoparticles: analysis of competitive and cooperative adsorption

In this research, zinc oxide (ZnO) nanoparticles synthesized using neem leaf (Azadirachta indica) extract were used as an adsorbent for removing two widely used pharmaceutical compounds acetaminophen (AMP) and sulfadiazine (SDZ). The synthesized ZnO nanoparticles were characterized using SEM-EDS, FTIR, TEM, BET, and XRD analysis. The synthesized ZnO nanoparticles were found to be in the size range of 10 nm with a surface area of 48.551 m²/g. The adsorptive performance of ZnO nanoparticles in both mono-component (MoS) and multi-component system (MuS) was investigated under various operational parameters viz. contact time, temperature, pH, concentration of pharmaceutical compound and ZnO nanoparticles dose. It was observed that the maximum adsorption capacity of ZnO nanoparticles was 7.87 mg/g and 7.77 mg/g for AMP and SDZ, respectively, under the optimum conditions of 7 pH and 2 g/L adsorbent dosage. The experimental data best-fitted with the pseudo-second-order model and Langmuir model, indicating monolayer chemisorption. Further investigation on removal of AMP and SDZ from multicomponent system was modelled using a Langmuir competitive model. The desorption study has shown 25.28% and 22.4% removal of AMP and SDZ from the surface of ZnO nanoparticles. In general, green synthesized ZnO nanoparticles can be utilized effectively as adsorbent for removal of pharmaceutically active compounds from wastewater.

Sono-Photocatalytic Activity of Cloisite 30B/ZnO/Ag2O Nanocomposite for the Simultaneous Degradation of Crystal Violet and Methylene Blue Dyes in Aqueous Media

A new nanocomposite based on Cloisite 30B clay modified with ZnO and Ag₂O nanoparticles (Cloisite 30B/ZnO/Ag₂O) was synthesized as an effective catalyst in the sono-photocatalytic process of crystal violet (CV) and methylene blue (MB) dyes simultaneously. The characteristics and catalytic activity of Cloisite 30B/ZnO/Ag₂O nanocomposite were investigated under different conditions. The specific active surface for Cloisite 30B/ZnO/Ag₂O nanocomposite was 18.29 m²/g. Additionally, the catalytic activity showed that Cloisite 30B/ZnO/Ag₂O nanocomposite (CV: 99.21%, MB: 98.43%) compared to Cloisite 30B/Ag₂O (CV: 85.38%, MB: 83.62%) and Ag₂O (CV: 68.21%, MB: 66.41%) has more catalytic activity. The catalytic activity of Cloisite 30B/ZnO/Ag₂O using the sono-photocatalytic process had the maximum efficiency (CV: 99.21%, MB: 98.43%) at pH 8, time of 50 min, amount of 40 mM H₂O₂, catalyst dose of 0.5 g/L, and the concentration of 'CV + MB' of 5 mg/L. The catalyst can be reused in the sono-photocatalytic process for up to six steps. According to the results, •OH and h⁺ were effective in the degradation of the desired dyes using the desired method. Data followed the pseudo-first-order kinetic model. The method used in this research is an efficient and promising method to remove dyes from wastewater.

Theoretical, Equilibrium, Kinetics and Thermodynamic Investigations of Methylene Blue Adsorption onto Lignite Coal

The interaction of methylene blue (MB) dye with natural coal (collected from coal landfills of the Kosovo Energy Corporation) in aqueous solutions was studied using adsorption, kinetics, and thermodynamic data, and Monte Carlo (MC) calculations. In a batch procedure, the effects of contact duration, initial MB concentration, pH, and solution temperature on the adsorption process were examined. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) isotherms were used to examine the equilibrium adsorption data. The equilibrium data fit well to the Freundlich and Langmuir adsorption isotherm models; however, the Freundlich model suited the adsorption data to a slightly better extent than the Langmuir model. The kinetics experimental data was fitted using pseudo-first-order, first-order, pseudo-second-order, second-order, Elvoich equation, and diffusion models. The pseudo-second-order rate model manifested a superlative fit to the experimental data, while the adsorption of MB onto coal is regulated by both liquid film and intraparticle diffusions at the same time. Thermodynamic parameters, such as Gibbs free energy (ΔG0), enthalpy (ΔH0), and entropy (ΔS0) were calculated. The adsorption of MB was confirmed to be spontaneous and endothermic. The theoretical results were in agreement with the experimental ones.