Graphene/ternary layered double hydroxide composites: Efficient removal of anionic dye from aqueous phase

Blending polydopamine-derived imprinted polymers with rice straw-based fluorescent carbon dots for selective detection and adsorptive removal of ibuprofen

Dual-functioning probes capable of detecting and removing hazardous substances have recently received increased attention compared to exclusive sensory probes. Herein, a new composite is synthesized by blending polydopamine imprinted polymers with fluorescent carbon dots (PIP-FCDs) for the selective recognition and adsorption of Ibuprofen (IBF). IBF is a nonsteroidal anti-inflammatory drug and is excessively released in the pharmaceutical wastes. The PIP-FCDs consist of confined pockets for encasing IBF and quenches fluorescence signal when contact with the molecule. PIP-FCDs show high sensitivity (limit of detection = 1.58 × 10-5 μM) and selectivity towards IBF in the presence of other pharmaceutical drugs i.e., aspirin, ketoprofen, norfloxacin, and levofloxacin. The adsorption studies show an adsorption capacity of 209.8 mg g-1 with an extraction efficiency of around 99.9 %. Furthermore, PIP-FCDs are utilized to determine IBF levels in various aqueous pharmaceutical samples. This development provides a simple and dual-functioning probe for the detection and adsorption of IBF from various matrices.

Integrated study of antiretroviral drug adsorption onto calcined layered double hydroxide clay: experimental and computational analysis

This study focused on the efficacy of a calcined layered double hydroxide (CLDH) clay in adsorbing two antiretroviral drugs (ARVDs), namely efavirenz (EFV) and nevirapine (NVP), from wastewater. The clay was synthesized using the co-precipitation method, followed by subsequent calcination in a muffle furnace at 500 °C for 4 h. The neat and calcined clay samples were subjected to various characterization techniques to elucidate their physical and chemical properties. Response surface modelling (RSM) was used to evaluate the interactions between the solution's initial pH, adsorbent loading, reaction temperature, and initial pollutant concentration. Additionally, the adsorption kinetics, thermodynamics, and reusability of the adsorbent were evaluated. The results demonstrated that NVP exhibited a faster adsorption rate than EFV, with both reaching equilibrium within 20-24 h. The pseudo-second order (PSO) model provided a good fit for the kinetics data. Thermodynamics analysis revealed that the adsorption process was spontaneous and exothermic, predominantly governed by physisorption interactions. The adsorption isotherms followed the Freundlich model, and the maximum adsorption capacities for EFV and NVP were established to be 2.73 mg/g and 2.93 mg/g, respectively. Evaluation of the adsorption mechanism through computational analysis demonstrated that both NVP and EFV formed stable complexes with CLDH, with NVP exhibiting a higher affinity. The associated adsorption energies were established to be -731.78 kcal/mol for NVP and -512.6 kcal/mol for EFV. Visualized non-covalent interaction (NCI) graphs indicated that hydrogen bonding played a significant role in ARVDs-CLDH interactions, further emphasizing physisorption as the dominant adsorption mechanism.

Potential of Capparis decidua plant and eggshell composite adsorbent for effective removal of anionic dyes from aqueous medium

The presence of hazardous dyes in wastewater poses significant threats to both ecosystems and the natural environment. Conventional methods for treating dye-contaminated water have several limitations, including high costs and complex operational processes. This study investigated a sustainable bio-sorbent composite derived from the Capparis decidua plant and eggshells, and evaluated its effectiveness in removing anionic dyes namely tartrazine (E-102), methyl orange (MO), and their mixed system. The research examines the influence of initial concentration, contact time, pH, adsorbent dosage, and temperature on the adsorption properties of anionic dyes. Optimal removal of tartrazine (E-102), methyl orange (MO), and their mixed system was achieved at a pH of 3. The equilibrium was achieved at 80 min for MO and mixed systems, and 100 min for E-102. The adsorption process showed an exothermic nature, indicating reduced capacity with increasing temperature, consistent with heat release during adsorption. Positive entropy values indicated increased disorder at the solid-liquid interface, attributed to molecular rearrangements and interactions between dye molecules and the adsorbent. Isotherm analysis using Langmuir, Freundlich, Temkin, and Redlich-Peterson models revealed that the Langmuir model best fit the experimental data. The maximum adsorption capacities of 50.97 mg/g, 52.24 mg/g, and 56.23 mg/g were achieved for E-102, MO, and the mixed system under optimized conditions, respectively. The pseudo-second-order kinetic model demonstrated the best fit, indicating that adsorption occurs through physical and chemical interactions such as electrostatic attraction, pore filling, and hydrogen bonding. Hence, the developed bio-sorbent could be a sustainable and cost-effective solution for the treatment of anionic dyes from industrial effluents.

Simultaneous adsorption of methylene blue and amoxicillin by starch-impregnated MgAl layered double hydroxide: Parametric optimization, isothermal studies and thermo-kinetic analysis

Textile and pharmaceutical effluents contain significant amounts of dyes and antibiotics, which pose a serious threat to the ecosystem when discharged directly. Therefore, they should be treated by facile treatment techniques using low-cost materials. Layered double hydroxide (LDH) and its hybrids have emerged as robust and economic adsorbents for water treatment. Herein, magnesium/aluminum LDH and its starch-based composite were synthesized by a co-precipitation technique. The physicochemical features of the developed adsorbents were thoroughly characterized using various analytical tools. The developed materials were tested for the eradication of methylene blue (MB) and amoxicillin (AMX) in batch mode adsorption by varying operating conditions. Adsorption performance depends on the solution's pH. Under optimum adsorption conditions of pH 11, adsorbent dosage of 50 mg/L, and treatment time of 120 min, starch-impregnated MgAl-LDH exhibited maximum MB and AMX adsorption capacities of 114.94 and 48.08 mg/g, respectively. The adsorption mechanism states that hydrogen bonds and weak van der Waals forces are responsible for the removal of pollutants by the developed materials. Moreover, equilibrium and kinetic studies revealed that the removal of dye and antibiotic followed the Freundlich and Langmuir models with the pseudo-second-order reaction kinetics, respectively. The spent adsorbents were regenerated using 0.1 M HCl (for MB) and methanol (for AMX) eluent, and reusability studies ensured that the developed adsorbents retained their performance for up to four consecutive adsorption/desorption cycles. MgAl-LDH and its starch-based hybrid could thus be used to effectively remove organic contaminants from wastewater streams on a commercial scale.

High-efficient and rapid removal of anionic and cationic dyes using a facile synthesized sole adsorbent NiAlFe-layered triple hydroxide (LTH)

It would be extremely momentous to familiarize a low-cost sole adsorbent NiAlFe-layered triple hydroxides (LTHs) having a strong sorption affinity towards both anionic and cationic dyes. Using the urea hydrolysis hydrothermal method LTHs were fabricated and by altering the ratio of participant metal cations the adsorbent was optimized. BET analysis revealed that the optimized LTHs possess an elevated surface area (160.04 m²/g) while TEM and FESEM analysis portrayed the stacked sheets-like 2D morphology. LTHs were employed for the amputation of anionic congo red (CR) and cationic brilliant green (BG) dye. The adsorption study showed that within 20 and 60 min, respectively, maximum adsorption capacities were achieved at 57.47 mg/g and 192.30 mg/g for CR and BG dye. Adsorption isotherm, kinetics, and thermodynamics study revealed that both chemisorptions with physisorptions were the assertive factor for the dye encapsulation. This enhanced adsorption performance of the optimized LTH for the anionic dye is attributed to its inherent anions exchange properties and new bond formation with the adsorbent skeleton. Whereas for the cationic dye, it was because of the formation of strong hydrogen bonds, and electrostatic interaction. Morphological manipulation of LTHs, formulates the optimized adsorbent LTH111, provokes the adsorbent for this elevated adsorption performance. Overall, this study revealed that LTHs have a high potential for the effectual remediation of dyes from wastewater as a sole adsorbent at a low cost.

Textural properties and adsorption behavior of Zn-Mg-Al layered double hydroxide upon crystal violet dye removal as a low cost, effective, and recyclable adsorbent

The preparation of adsorbents plays a vital role in the adsorption method. In particular, many adsorbents with high specific surface areas and unique shapes are essential for the adsorption strategy. A Zn-Mg-Al/layer double hydroxide (LDH) was designed in this study using a simple co-precipitation process. Adsorbent based on Zn-Mg-Al/LDH was used to remove crystal violet (CV) from the wastewater. The impacts of the initial dye concentration, pH, and temperature on CV adsorption performance were systematically examined. The adsorbents were analyzed both before and after adsorption using FTIR, XRD, and SEM. The roughness parameters and surface morphologies of the produced LDH were estimated using 3D SEM images. Under the best conditions (dose of adsorbent = 0.07 g and pH = 9), the maximum adsorption capacity has been achieved. Adsorption kinetics studies revealed that the reaction that led to the adsorption of CV dye onto Zn-Mg-Al/LDH was a pseudo-second-order model. Additionally, intraparticle diffusion suggests that Zn-Mg-Al/LDH has a fast diffusion constant for CV molecules (0.251 mg/(g min^1/2)). Furthermore, as predicted by the Langmuir model, the maximal Zn-Mg-Al/LDH adsorption capacity of CV was 64.80 mg/g. The CV dimensionless separation factor (R_L) onto Zn-Mg-Al/LDH was 0.769, indicating that adsorption was favorable. The effect of temperature was performed at 25, 35, and 45 °C in order to establish the thermodynamic parameters ∆H^o, ∆S^o, and ∆G^o. The computed values indicated exothermic and spontaneous adsorption processes. The study presented here might be used to develop new adsorbents with enhanced adsorption capabilities for the purpose of protecting the water environment.

Magnesium/aluminum layered double hydroxides intercalated with starch for effective adsorptive removal of anionic dyes

In this research, the adsorptive performance of a starch-magnesium/aluminum layered double hydroxide (S-Mg/Al LDH) composite was investigated for different organic dyes in single-component systems by conducting a series of batch mode experiments. S-Mg/Al LDH composite showed preferential adsorption of anionic dyes than cationic dyes. The marked impact of key process variables (e.g., contact time, adsorbent dosage, pH, and temperature) on its adsorption was investigated. Multiple isotherms, kinetics, and thermodynamic models were applied to describe adsorption behavior, diffusion, and uptake rates of the organic dyes over S-Mg/Al LDH composite. A better fitting of the non-linear Langmuir model reflects the predominance of monolayered adsorption of dye molecules on the composite surface. Partition coefficients (mg g^-1 μM^-1) for S-Mg/Al LDH were observed in the following descending order: Amaranth (665) > Tartrazine (186) > Sunset yellow (71) > Eosin yellow (65). Furthermore, comparative evaluation of the adsorption enthalpy, entropy, and Gibbs free energy values indicates that the adsorption process is spontaneous and exothermic. S-Mg/Al LDH composite maintained a stable adsorption/desorption recycling process over six consecutive cycles with the advantages of low cost, chemical/mechanical stability, and easy recovery. The results of this study are expected to expand the application of modified LDHs toward wastewater treatment.

Remediation of Cd (II) Ion from an Aqueous Solution by a Starch-Based Activated Carbon: Experimental and Density Functional Theory (DFT) Approach

Heavy metal ion pollution is a serious threat for aquatic and terrestrial living beings. Adsorption is a facile process to encounter heavy metal pollution. Various types of adsorbents have been developed and used for environmental remediation. Activated carbon is one of the cheapest adsorbents derived from various biomass. In this work, the adsorption of cadmium ions (Cd (II)) with starch-based activated carbon (AC) having a specific surface area of 1600 m2 g−1 was investigated in a series of batch laboratory studies. The effective operating parameters, such as initial pH (pH0), initial concentration of metal ions, contact time, and temperature on the adsorption, were investigated. Validation of the kinetic study shows that the adsorption process is better predicted by the pseudo-second-order model. The extended Freundlich and Langmuir isotherms were applied to the study. The results show that the metal ion adsorption capacities of activated carbon increased with increasing pH, and it was found that maximum adsorption (284 mg g−1) of Cd (II) was achieved at pH solution of 5.5–6. The thermodynamic parameters, such as ∆G, ∆H, and ∆S, were found to be −17.42 kJ mol−1, 8.49 kJ mol−1, and 58.66 J mol−1 K−1, respectively, revealing that the adsorption mechanism is endothermic, spontaneous, and feasible. Furthermore, the density functional theory simulations demonstrated that the activated carbon strongly interacted with toxicity and mobility, so it is very urgent to remove this species from industrial wastewater before it is discharged into the environment. The adsorption energy calculated for all interactive sites was negative (−43.41 kJ mol−1 to −967.74 kJ mol−1), showing effective interaction between the adsorbate and adsorbent. The PDOS clearly shows that there is a stronger overlapping at the Femi level between the d orbital of the Cd ion and the p orbital of the O atom, showing a strong interaction and confirming the chemical bond formation between the Cd (II) ion and O atom.

Process Optimization and Modeling of Phenol Adsorption onto Sludge-Based Activated Carbon Intercalated MgAlFe Ternary Layered Double Hydroxide Composite

A sewage sludge-based activated carbon (SBAC) intercalated MgAlFe ternary layered double hydroxide (SBAC-MgAlFe-LDH) composite was synthesized via the coprecipitation method. The adsorptive performance of the composite for phenol uptake from the aqueous phase was evaluated via the response surface methodology (RSM) modeling technique. The SBAC-MgAlFe-LDH phenol uptake capacity data were well-fitted to reduced RSM cubic model (R² = 0.995, R²-adjusted = 0.993, R²-predicted = 0.959 and p-values < 0.05). The optimum phenol adsorption onto the SBAC-MgAlFe-LDH was achieved at 35 °C, 125 mg/L phenol, and pH 6. Under the optimal phenol uptake conditions, pseudo-first-order and Avrami fractional-order models provided a better representation of the phenol uptake kinetic data, while the equilibrium data models’ fitting follows the order; Liu > Langmuir > Redlich–Peterson > Freundlich > Temkin. The phenol uptake mechanism was endothermic in nature and predominantly via a physisorption process (ΔG° = −5.33 to −5.77 kJ/mol) with the involvement of π–π interactions between the phenol molecules and the functionalities on the SBAC-LDH surface. The maximum uptake capacity (216.76 mg/g) of SBAC-MgAlFe-LDH was much higher than many other SBAC-based adsorbents. The improved uptake capacity of SBAC-LDH was attributed to the effective synergetic influence of SBAC-MgAlFe-LDH, which yielded abundant functionalized surface groups that favored higher aqueous phase uptake of phenol molecules. This study showcases the potential of SBAC-MgAlFe-LDH as an effective adsorbent material for remediation of phenolic wastewater

Removal of azo dye from aqueous solution by a low-cost activated carbon prepared from coal: adsorption kinetics, isotherms study, and DFT simulation

The high-risk organic pollutants produced by industries are of growing concern. The highly porous coal-based activated carbon (AC) having a specific surface area of 3452.8 m²/g is used for the adsorption of azo dye from synthetic solution. The sorbent is characterized through BET, SEM, TEM, XRD, FT-IR, TGA, and zeta potential. The sorbent exhibits - 18.7 mV surface charge, which is high enough for making suspension. The maximum dye uptake of 333 mg/g is observed in sorbent under acidic medium. The thermodynamics parameters like ∆G, ∆H, and ΔS were found to be - 12.40 kJ mol^-1, 39.66 kJ mol^-1, and 174.55 J mol^-1 K^-1 at 293 K, respectively, revealing that the adsorption mechanism is spontaneous, endothermic, and feasible. The experimental data follows the Langmuir and D-R models. The adsorption follows pseudo 2nd-order kinetics. DFT investigation shows that the dye sorption onto AC in configuration No. 4 (CFG-4) is more effective, as this configuration has high ∆H (enthalpy change) and adsorption energy (E_ads). This is confirmed by Mullikan atomic charge transfer phenomenon.

Magnetic Mg-Fe/LDH Intercalated Activated Carbon Composites for Nitrate and Phosphate Removal from Wastewater: Insight into Behavior and Mechanisms

This experimental work focused on the synthesis, characterization, and testing of a unique, magnetically separable, and eco-friendly adsorbent composite material for the advanced treatment and efficient removal of nitrate and phosphate pollutants from wastewater. The MgAl-augmented double-layered hydroxide (Mg-Fe/LDH) intercalated with sludge-based activated carbon (SBAC-MgFe) composites were characterized by FT-IR, XRD, BET, VSM, SEM, and TEM techniques, revealing homogeneous and efficient dispersion of MgFe/LDH within the activated carbon (AC) matrix, a highly mesoporous structure, and superparamagnetic characteristics. The initial solution pH, adsorbent dose, contact time, and temperature parameters were optimized in order to reach the best removal performance for both pollutants. The maximum adsorption capacities of phosphate and nitrate were found to be 110 and 54.5 mg/g, respectively. The competition between phosphate and coexisting ions (Cl⁻, CO₃²⁻, and SO₄²⁻) was studied and found to be remarkably lower in comparison with the nitrate adsorption. The adsorption mechanisms were elucidated by kinetic, isotherm, thermodynamic modeling, and post-adsorption characterizations of the composite. Modeling and mechanistic studies demonstrated that physisorption processes such as electrostatic attraction and ion exchange mainly governed the nitrate and phosphate adsorption. The composite indicated an outstanding regeneration performance even after five sequences of adsorption/desorption cycles. The fabricated composite with magnetically separable characteristics can be used as a promising adsorbent for the removal of phosphate and nitrate pollutants from wastewater.

Sewage Sludge ZnCl2-Activated Carbon Intercalated MgFe-LDH Nanocomposites: Insight of the Sorption Mechanism of Improved Removal of Phenol from Water

Keywords: sludge-activated carbon; MgFe layered double hydroxide; nanocomposite materials; phenol aqueous uptake; mechanistic studies; reusability performance.

Comparative Adsorptive Removal of Phosphate and Nitrate from Wastewater Using Biochar-MgAl LDH Nanocomposites: Coexisting Anions Effect and Mechanistic Studies

In this study, date-palm biochar MgAl-augmented double-layered hydroxide (biochar-MgAl-LDH) nanocomposite was synthesized, characterized, and used for enhancing the removal of phosphate and nitrate pollutants from wastewater. The biochar-MgAl-LDH had higher selectivity and adsorption affinity towards phosphate compared to nitrate. The adsorption kinetics of both anions were better explained by the pseudo-first-order model with a faster removal rate to attain equilibrium in a shorter time, especially at lower initial phosphate-nitrate concentration. The maximum monolayer adsorption capacities of phosphate and nitrate by the non-linear Langmuir model were 177.97 mg/g and 28.06 mg/g, respectively. The coexistence of anions (Cl-, SO42-, NO3-, CO32- and HCO3-) negligibly affected the removal of phosphate due to its stronger bond on the nano-composites, while the presence of Cl- and PO43- reduced the nitrate removal attributed to the ions' participation in the active adsorption sites on the surface of biochar-MgAl-LDH. The excellent adsorptive performance is the main synergetic influence of the MgAl-LDH incorporation into the biochar. The regeneration tests confirmed that the biochar-MgAl composite can be restored effortlessly and has the prospective to be reused after several subsequent adsorption-desorption cycles. The biochar-LDH further demonstrated capabilities for higher removal of phosphate and nitrate from real wastewater.

Cu-Deficient plasmonic Cu2−xS nanocrystals induced tunable photocatalytic activities

Cu-Deficient plasmonic Cu_2−xS nanocrystals with tunable photocatalytic activities were synthesized and investigated.