Date palm ash-MgAl-layered double hydroxide composite: sustainable adsorbent for effective removal of methyl orange and eriochrome black-T from aqueous phase

Synthesis of LDH-MgAl and LDH-MgFe composites for the efficient removal of the antibiotic from water

In this study, novel lamellar double hydroxide composites (LDH-MgAl and LDH-MgFe) were synthesized at different metal salt ratios (1:1 to 3:1) and fully characterized using various techniques such as XRD, FTIR, SEM, EDS, and TGA. The resulting LDHs demonstrated a high affinity for efficiently removing tetracycline (TC) antibiotic from water, particularly at a moderate molar ratio of 3:1. This ratio exhibited improved structural characteristics, resulting in better TC uptake from water. The improved performance was supported by the increased abundance of surface functional groups (OH, NO3, CO32-, C-O-C, Fe-O, and Al-O-Al). The TGA analysis established the high stability of the LDHs when subjected to high temperatures. The kinetics of TC adsorption onto LDH fitted with the PSO (R2 = 0.935-0.994) and Avrami (R2 = 0.9528-0.9824) models, while the equilibrium data fitted the Liu and Langmuir isotherm models, with maximum monolayer adsorption capacities of 101.1 mg g-1 and 70.83 mg g-1, respectively-significantly higher than many reported values in the literature. The positive values of ΔH0 and ΔS0 indicate an endothermic process, with TC removal mechanisms influenced by physical interactions, such as hydrogen bonding, electrostatic interaction, and π-cation with the surface functional groups of the LDH adsorbents. These results suggest that LDH-MgAl and LDH-MgFe are promising adsorbents for the removal of TC from water.

Preparation of composites with MgAl-LDH-modified commercial activated carbon for the quick removal of Cr(VI) from aqueous solutions

The problem of soil and water contamination caused by Cr(VI) discharged from the dyeing, electroplating, and metallurgical industries is becoming increasingly serious, posing a potentially great threat to the environment and public health. Therefore, it is crucial to develop a fast, efficient, and cost-effective adsorbent for remediating Cr-contaminated wastewater. In this work, MgAl-LDH/commercial-activated carbon nanocomposites (LDH-CACs) are prepared with hydrothermal. The effects of preparation and reaction conditions on the composite properties are first investigated, and then its adsorption behavior is thoroughly explored. Finally, a potential adsorption mechanism is proposed by several characterizations like SEM-EDS, XRD, FTIR, and XPS. The removal of Cr(VI) reaches 72.47% at optimal conditions, and the adsorption study demonstrates that LDH-CAC@1 has an extremely rapid adsorption rate and a maximum adsorption capacity of 116.7 mg/g. The primary removal mechanisms include adsorption-coupled reduction, ion exchange, surface precipitation, and electrostatic attraction. The reusability experiment illustrates that LDH-CAC@1 exhibits promising reusability. This study provides an effective adsorbent with a remarkably fast reaction, which has positive environmental significance for the treatment of Cr(VI) wastewater.

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

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

Phosphate recovery from sludge-incinerated ash by adsorption with hydrotalcite synthesized by metals in the ash

Selective adsorption of phosphorus (P) from the acidic leachate of sludge-incinerated ash (SIA) becomes more attractive due to avoiding removing heavy metals. Especially, layered double hydroxides (LDHs) as an anion adsorbent could be applied into this area owing to their good capacity on P-adsorption and low cost on preparation. Interestingly, SIA contains more aluminum (Al) and iron (Fe) needed to be removed prior to P-recovery, and removed Al and Fe could be utilized to synthesize LDHs, like Mg/Al-LDH and Mg/Fe-LDH. With this study, Mg/Al-LDH-r and Mg/Fe-LDH-r were economically synthesized with Al and Fe removed from SIA, which were similar in their chemical structures to commercial LDHs. The synthesized LDHs had a high P-adsorption capacity, up to 95.0%. The maximal phosphate capacity of the recovered LDHs (Mg/Al-LDH-r and Mg/Fe-LDH-r) was 239.0 and 199.8 mg P/g LDHs, respectively. "NaOH + desalinated brine" as a new desorption solution could achieve a desorption ratio at about 80%, which could reduce the liquid-solid ratio by at least 60%, greatly decreasing the desorption cost. Pot trials demonstrated that the desorbed and precipitated CaP could promote the growth of maize as well as a commercial P-fertilizer. Furthermore, the adsorbed phosphate by LDHs could be directly used as a slow-released P-fertilizer and also improve the pH value of acidic soil, completely deleting the desorption process.

Adsorption of methyl orange on low-cost adsorbent natural materials and modified natural materials: a review

Recently a large number of extensive studies have amassed that describe the removal of dyes from water and wastewater using natural adsorbents and modified materials. Methyl orange dye is found in wastewater streams from various industries that include textiles, plastics, printing and paper among other sources. This article reviews methyl orange adsorption onto natural and modified materials. Despite many techniques available, adsorption stands out for efficient water and wastewater treatment for its ease of operation, flexibility and large-scale removal of colorants. It also has a significant potential for regeneration recovery and recycling of adsorbents in comparison to other water treatment methods. The adsorbents described herein were classified into five categories based on their chemical composition: bio-sorbents, activated carbon, biochar, clays and minerals, and composites. In this review article, we want to demonstrate the capacity of natural and modified materials for dye adsorption which can yield significant improvements to the adsorption capacity of dyes such as methyl orange. In addition, the effect of critical variables including contact time, initial methyl orange concentration, dosage of adsorbent, pH, temperature and mechanism on the adsorption efficiency will be covered as part of this literature review.

Cationic dialdehyde cellulose microfibers for efficient removal of eriochrome black T from aqueous solution

Materials based on cellulose have been widely used as a decontaminant agent of wastewater. However, it can not be found in the literature any application of the cationic dialdehyde cellulose (cDAC) in anionic dye removal. Therefore, this study aims a circular economy concept using sugarcane bagasse to obtain a functionalized cellulose by oxidation and cationization. cDAC was characterized by SEM, FT-IR, oxidation degree, and DSC. Adsorption capacity was evaluated by pH, kinetic, concentration effect, strength ionic tests, and recycling. The kinetic followed Elovich model (R² = 0.92605 for EBT = 100 mg/L) and non-linear Langmuir model (R² = 0.94542), which resulted in a maximum adsorption capacity of 563.30 mg/g. The cellulose adsorbent reached an efficient recyclability of 4 cycles. Thus, this work presents a potential material to become a new, clean, low-cost, recyclable, and environmentally friendly alternative for effluent decontamination-containing dyes.

Efficient Adsorption Capacity of MgFe-Layered Double Hydroxide Loaded on Pomelo Peel Biochar for Cd (II) from Aqueous Solutions: Adsorption Behaviour and Mechanism

A novel pomelo peel biochar/MgFe-layered double hydroxide composite (PPBC/MgFe-LDH) was synthesised using a facile coprecipitation approach and applied to remove cadmium ions (Cd (II)). The adsorption isotherm demonstrated that the Cd (II) adsorption by the PPBC/MgFe-LDH composite fit the Langmuir model well, and the adsorption behaviour was a monolayer chemisorption. The maximum adsorption capacity of Cd (II) was determined to be 448.961 (±12.3) mg·g^-1 from the Langmuir model, which was close to the actual experimental adsorption capacity 448.302 (±1.41) mg·g^-1. The results also demonstrated that the chemical adsorption controlled the rate of reaction in the Cd (II) adsorption process of PPBC/MgFe-LDH. Piecewise fitting of the intra-particle diffusion model revealed multi-linearity during the adsorption process. Through associative characterization analysis, the adsorption mechanism of Cd (II) of PPBC/MgFe-LDH involved (i) hydroxide formation or carbonate precipitation; (ii) an isomorphic substitution of Fe (III) by Cd (II); (iii) surface complexation of Cd (II) by functional groups (-OH); and (iv) electrostatic attraction. The PPBC/MgFe-LDH composite demonstrated great potential for removing Cd (II) from wastewater, with the advantages of facile synthesis and excellent adsorption capacity.

Hollow @CuMgAl double layered hydrotalcites and mixed oxides with tunable textural and structural properties, and thus enhanced NH3-NOx-SCR activity

Well-organized, spherical, mesoporous hollow @CuMgAl-LDHs (layered double hydroxides) are prepared by the controlled removal of the SiO₂ from SiO₂@CuMgAl-LDH core-shell hybrids that in turn are synthesized via a bottom-up strategy. The materials are prepared with various Cu/Mg molar ratios (Cu/Mg = 0.05-0.50) while keeping the ratio of Cu and Mg constant, (Cu + Mg)/Al = 2. The effect of Cu doping and the silica core removal process (conducted for 4 h at 30 °C using 1 M NaOH) on the chemical composition, morphology, structure, texture and reducibility of the resulting materials are described. @CuMgAl-MOs (mixed oxides) obtained by thermal treatment of the @CuMgAl-LDHs are active and selective catalysts for the selective catalytic reduction of NO_x using ammonia, and effectively operate at low temperatures. The N₂ yield increases with increased Cu content in the CuMgAl shell, which is associated with the easier reducibility of the Cu species incorporated into the MgAl matrix. @CuMgAl-MOs show better catalytic performance than bulk CuMgAl MOs.

Adsorption of the First-Line Covid Treatment Analgesic onto Activated Carbon from Residual Pods of Erythrina Speciosa

In this study, the residual pods of the forest species Erythrina speciosa were carbonized with ZnCl₂ to obtain porous activated carbon and investigated for the adsorptive removal of the drug paracetamol (PCM) from water. The PCM adsorption onto activated carbon is favored at acidic solution pH. The isothermal studies confirmed that increasing the temperature from 298 to 328 K decreased the adsorption capacity from 65 mg g^-1 to 50.4 mg g^-1 (C₀ = 175 mg L^-1). The Freundlich model showed a better fit of the equilibrium isotherms. Thermodynamic studies confirmed the exothermic nature (ΔH⁰ = -39.1066 kJ mol^-1). Kinetic data indicates that the external mass transfer occurs in the first minutes followed by the surface diffusion, considering that the linear driving force model described the experimental data. The application of the material in the treatment of a simulated effluent with natural conditions was promising, presenting a removal of 76.45%. Therefore, it can be concluded that the application of residual pods of the forest species Erythrina speciosa carbonized with ZnCl₂ is highly efficient in the removal of the drug paracetamol and also in mixtures containing other pharmaceutical substances.

A Comprehensive Review on Adsorption, Photocatalytic and Chemical Degradation of Dyes and Nitro-Compounds over Different Kinds of Porous and Composite Materials

Dye and nitro-compound pollution has become a significant issue worldwide. The adsorption and degradation of dyes and nitro-compounds have recently become important areas of study. Different methods, such as precipitation, flocculation, ultra-filtration, ion exchange, coagulation, and electro-catalytic degradation have been adopted for the adsorption and degradation of these organic pollutants. Apart from these methods, adsorption, photocatalytic degradation, and chemical degradation are considered the most economical and efficient to control water pollution from dyes and nitro-compounds. In this review, different kinds of dyes and nitro-compounds, and their adverse effects on aquatic organisms and human beings, were summarized in depth. This review article covers the comprehensive analysis of the adsorption of dyes over different materials (porous polymer, carbon-based materials, clay-based materials, layer double hydroxides, metal-organic frameworks, and biosorbents). The mechanism and kinetics of dye adsorption were the central parts of this study. The structures of all the materials mentioned above were discussed, along with their main functional groups responsible for dye adsorption. Removal and degradation methods, such as adsorption, photocatalytic degradation, and chemical degradation of dyes and nitro-compounds were also the main aim of this review article, as well as the materials used for such degradation. The mechanisms of photocatalytic and chemical degradation were also explained comprehensively. Different factors responsible for adsorption, photocatalytic degradation, and chemical degradation were also highlighted. Advantages and disadvantages, as well as economic cost, were also discussed briefly. This review will be beneficial for the reader as it covers all aspects of dye adsorption and the degradation of dyes and nitro-compounds. Future aspects and shortcomings were also part of this review article. There are several review articles on all these topics, but such a comprehensive study has not been performed so far in the literature.

Engineered biochar supported layered double hydroxide-cellulose nanocrystals composite-: Synthesis, characterization and azo dye removal performance

In this work, engineered biochar decorated layered double hydroxides and cellulose nanocrystals (B-CuFe-CNC) biocomposites were synthesized by the facile ultrasonicated-co-precipitation technique. The biocomposite was investigated for purification of Eriochrome Black T (EBT) dye from water. The characterization results showed that the presence of CNC in biochar-layered double hydroxides resulted in a two-dimensional rod-like structure with excellent crystallinity, improved surface functionalities, and provides an attractive platform for the enhanced adsorption of azo anionic dye molecules. The adsorption system was appropriately demonstrated by the BBD-RSM (R² > 0.994). The biocomposite exhibited higher EBT adsorption in the acidic pH range (2-5) due to strong electrostatic and chemical interactions. The kinetic and isotherm results were well demonstrated by pseudo-second order, Freundlich, and Redlich Peterson models. The maximum adsorption capacity of biocomposite was 876.2 mg/g achieved within 45 min. The spectroscopic analyses imply that the high removal of EBT by biocomposite is mainly governed by electrostatic attraction, hydrogen bonding, and chemical/metal complexation mechanisms. The biocomposite maintained high EBT removal after six successive adsorption cycles and excellent dye adsorption in the different water matrices. The results suggest that tailoring biochar properties with layered double hydroxide and CNC is a promising way for the enhanced removal of dye contaminants from wastewater.

Enhanced removal of Eriochrome Black T from water using biochar/layered double hydroxide/chitosan hybrid composite: Performance evaluation and optimization using BBD-RSM approach

In this research work, a novel hybrid composite consisting of biochar (B), layered double hydroxide (CuFe) and chitosan (CS) (B-CuFe-CS) was produced using an ultrasonication-assisted co-precipitation method. The resultant composite was employed for adsorptive removal of Eriochrome black T (EBT) from water. Physicochemical characterization indicated that the B-CuFe-CS containing 10 wt % CS exhibited a heterogeneous structure with better crystallographic and textural characteristics. The B-CuFe-CS with abundant surface functionalities (-CO, -C-O, -OH, -NO_3, and MMO), facilitates faster and enhanced removal of the EBT. The kinetic results showed better fitting to the pseudo-second order model, and equilibrium was achieved within 30 min. Equilibrium data was well explained by Langmuir and Redlich Peterson isotherm models (R² > 0.98), indicating the EBT removal onto B-CuFe-CS followed monolayer adsorption. The maximum adsorption capacity was 806.4 mg/g, which was higher than pristine B-CuFe (476.19 mg/g) and many other adsorbents. The spectroscopic analysis (FTIR and XPS) and experimental results suggested that EBT adsorption is mainly governed by electrostatic, chemical and anion-exchange interactions. It is evident from these results that coupling B-CuFe composite with bio-filler (chitosan) resulted in an efficient bio-adsorbent to effectively purify dye-contaminated water streams.

Recent advances in waste-derived functional materials for wastewater remediation

Water pollution is a major concern for public health and a sustainable future. It is urgent to purify wastewater with effective methods to ensure a clean water supply. Most wastewater remediation techniques rely heavily on functional materials, and cost-effective materials are thus highly favorable. Of great environmental and economic significance, developing waste-derived materials for wastewater remediation has undergone explosive growth recently. Herein, the applications of waste (e.g., biowastes, electronic wastes, and industrial wastes)-derived materials for wastewater purification are comprehensively reviewed. Sophisticated strategies for turning wastes into functional materials are firstly summarized, including pyrolysis and combustion, hydrothermal synthesis, sol-gel method, co-precipitation, and ball milling. Moreover, critical experimental parameters within different design strategies are discussed. Afterward, recent applications of waste-derived functional materials in adsorption, photocatalytic degradation, electrochemical treatment, and advanced oxidation processes (AOPs) are analyzed. We mainly focus on the development of efficient functional materials via regulating the internal and external characteristics of waste-derived materials, and the material's property-performance correlation is also emphasized. Finally, the key future perspectives in the field of waste-derived materials-driven water remediation are highlighted.

The boosted activity of AgI/BiOI nanocatalyst: a RSM study towards Eriochrome Black T photodegradation

Nowadays, critical environmental pollution needs some novel, simple, effective, and cost-effective catalysts with high efficiency in the visible region of the light. Thus, the AgI/BiOI coupled nanocatalyst sample (CS) was prepared and briefly characterized. The pH_pzc values of 6.2, 5.4, and 4.5 were estimated for AgI, BiOI, and AgI/BiOI samples. Based on the PXRD results, average crystallite sizes of 35.2, 34.7, and 34.1 nm were obtained for AgI, BiOI, and AgI/BiOI samples from the Scherrer formula and 38.3, 25.6, and 25.6 nm by the Williamson-Hall formula. SEM image confirmed a sheet-like BiOI morphology covered by AgI nanoparticles. The simultaneous interactions of the influencing variables on the boosted photocatalytic activity of CS sample towards Eriochrome Black T (EBT) were evaluated by response surface methodology (RSM) (under 100-W tungsten lamp irradiation with 230 mW/m².nm irradiance). The goodness of the model was confirmed by the significance of the model (F value of 65.68 > F_{0.05, 14, 13} = 2.55) and a non-significant LOF (F value of 0.97 < F_{0.05, 10, 3} = 8.79) at a 95% confidence interval obtained in ANOVA analysis of the results. The center point runs have the following conditions: catalyst dose: 0.68 g/L; pH: 7.5; C_EBT: 7.25 mg/L; and irradiation time: 53.5 min, while the optimal run included the following conditions: catalyst dose: 1.0 g/L; pH: 4; C_EBT: 10 mg/L; and irradiation time: 80 min. About 95% of EBT molecules were degraded in the optimal conditions.

Insight into ANN and RSM Models’ Predictive Performance for Mechanistic Aspects of Cr(VI) Uptake by Layered Double Hydroxide Nanocomposites from Water

Mathematical predictive models are vital tools for understanding of pollutant uptake during adsorptive water and wastewater treatment processes. In this study, applications of CoAl-LDH and its bentonite-CoAl intercalated LDH (bentonite-CoAl-LDH) for uptake of Cr(VI) from water were modeled using response surface methodology (RSM) and artificial neural network (ANN), and their performance for predicting equilibrium, thermodynamics and kinetics of the Cr(VI) uptake were assessed and compared based on coefficient of determination (R2) and root mean square error (RMSE). The uptake of Cr(VI) fits well quartic RSM polynomial models and ANN models based on Levenberg–Marquardt algorithms (ANN-LMA). Both models predicted a better fit for the Langmuir model compared to the Freundlich model for the Cr(VI) uptake. The predicted non-linear Langmuir model contestant (KL) values, for both the RSM and ANN-LMA models yielded better ΔG°, ΔH and ΔS predictions which supported the actual feasible, spontaneous and greater order of reaction as well as exothermic nature of Cr(VI) uptake onto the tested adsorbents. Employing the linear Langmuir model KL values dwindles the thermodynamic parameter predictions, especially for the RSM models. The excellent kinetic parameter predictions for the ANN-LMA models further indicate a mainly pseudo-second-order process, thus confirming the predominant chemisorption mechanism as established by the Cr(VI) speciation and surface charges for the Cr(VI) uptake by both CoAl-LDH and bentonite-CoAl-LDH. The ANN-LMA models showed consistent and insignificant decline in their predictions under different mechanistic studies carried out compared to the RSM models. This study demonstrates the high potential reliability of ANN-LMA models in capturing Cr(VI) adsorption data for LDHs nanocomposite heavy metal uptake in water and wastewater treatment.

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.

Recent progress in the synthesis of Layered Double Hydroxides and their application for the adsorptive removal of dyes: A review

Layered double hydroxides (LDHs), also known as anionic clays, are lamellar inorganic solids with a brucite-like structure and consist of positively charged metal hydroxide sheets intercalated by anions and water molecules. Choice of LDH is beneficial as it displays properties like simple synthesis procedures, adjustable structure, stability, large surface area, homogeneous positive charge distribution over the surface, interplanar spacing, and versatility to synthesize a variety of composites. Due to these properties LDHs act as efficient adsorbents for wastewater treatment. This review presents a detailed overview of the removal of hazardous organic dyes using different LDHs and LDH-hybrids/composites. The review also incorporates methods of synthesis of various LDHs and composites and the effect of their morphology on dye removal capacity. The effects of adsorption variables such as pH, adsorbent dosage, initial concentration of dye, contact time on the adsorption of these materials are also explained along with adsorption isotherms, kinetics and operative mechanisms. This article incorporates 156 references, majority of which have been taken from the available literature of last 5 years.

Simultaneous Methylene Blue Adsorption and pH Neutralization of Contaminated Water by Rice Husk Ash

In this study, the potential of rice husk ash (RHA) to act as an adsorbent for treating dye-containing wastewater was demonstrated. The RHA used in this study contained 91.7% silica, which was composed of crystalline (cristobalite and tridymite) and amorphous phases. The mechanochemical treatment of RHA led to an increase in its specific surface area from 6.2 to 14.6 m²/g in 15 min and dramatically improved its methylene blue (MB) adsorption ability. Langmuir adsorption isotherms revealed that the maximum adsorption capacity of the treated RHA was 8.59 mg/g, which is 2.45 times higher than that of raw RHA. pH-dependent adsorption studies on the RHA revealed that MB was adsorbed on the deprotonated Q³ silanol through electrostatic interactions. Moreover, the RHA adsorbent showed pH buffering at a pH value of approximately 7; thus, the pH of the solution could be neutralized simultaneously with the adsorptive removal of MB.

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

Nano and micro architectured cues as smart materials to mitigate recalcitrant pharmaceutical pollutants from wastewater

Pharmaceuticals have been recognized for saving billions of lives, but they also appear as a novel group of environmental pollutants. The presence of pharmaceutically active residues in seawater, surface water, wastewater treatment plants, sludges, and soils has been widely reported. Their persistence in the environment for extended durations exerts various adverse consequences, such as gene toxicity, hormonal interference, antibiotic resistance, sex organs imposition, and many others. Various methodologies have been envisioned for their removal from the aqueous media. Different processes have been restricted due to high cost, inefficient removal, generation of toxic materials, and high capital requirement. The employment of nanostructured materials to mitigate pharmaceutical contaminants has been increasing during the last decades. The adsorptive nanomaterials have a high surface area, low cost, eco-friendliness, and high affinity for inorganic and organic molecules. In this review, we have documented the rising concerns of environmental pharmaceutical contamination and their remediation by applications of nanomaterials. Nanomaterials could be a robust candidate for the removal of an array of environmental contaminants in water.

Hybrid MnFe-LDO-biochar nanopowders for degradation of metronidazole via UV-light-driven photocatalysis: Characterization and mechanism studies

A cost-competitive MnFe-LDO-biochar hybrid catalyst was successfully synthesized via a simple yet efficient technique for the decomposition of metronidazole (MZ). MnFe-LDO-biochar was characterized by various techniques and the results revealed that it has a bandgap of 2.85 eV, high photocurrent response of 3.8 μA cm^-2 and can be separated rapidly from the bulk solution by an external magnet due to its saturation magnetization of 28.5 emu g^-1. Initially, in the dark condition, 20% of MZ was removed after 30 min when 20 mg L^-1 MZ solution was treated with 50 mg MnFe-LDO-biochar in the presence of 6 mM H₂O₂. The MZ degradation increased remarkably to ∼98% upon exposure to a UV light for 60 min. Under various processes, UV/MnFe-LDO-biochar/H₂O₂ presented high degradation rate constant of 0.226 min^-1 and lowest energy consumption cost of 0.38$ at 7.56 kWh m^-3 which is ∼13 times lower than the degradation of MZ by the photolytic process under similar conditions. The MZ photocatalytic decomposition trend revealed a multiprocess mechanism influenced majorly by ^•OH and partly by h⁺ and ^•O₂^-. Note that in MnFe-LDO-biochar/UV system; 5% of MZ degradation was observed after 120 min and reached 13% after 300 min. MnFe-LDO-biochar maintained ∼88% reuse efficiency after three consecutive recycling tests.

Removal of organic dyes from wastewater using Eichhornia crassipes: a potential phytoremediation option

Wastewater from textile industries is a potential source of organic dyes in natural water bodies. Environmental concerns of chemical methods for removal of dyes from wastewater are no more a viable solution, and there is growing concern to develop alternative approaches such as green chemistry and phytoremediation. This study reports the removal of organic dyes from wastewater using Eichhornia crassipes (Mart.) Solms (water hyacinth), as an easily available and fast-growing plant species. Growth of water hyacinth among individual cationic (rose bengal (RB), methylene blue (MB), crystal violet (CV), auramine O (AO), rhodamine B (RhB) and anionic (xylenol orange (XO), phenol red (PR), cresol red (CR), methyl orange (MO)) dye solutions and degradation of dyes were monitored. Results indicated that water hyacinth has good absorption and degradation potential for both types of dyes (cationic or anionic) and effectively removes dyes from solution. Water hyacinth can be used as a suitable and effective phytoremediate for removal of organic dyes from the wastewater.Graphical abstract.

Comparative adsorption capabilities of rubbish tissue paper-derived carbon-doped MgO and CaCO3 for EBT and U(VI), studied by batch, spectroscopy and DFT calculations

Water pollution due to organic dyes and radionuclides is a challenging issue to the modern world. Cheap and efficient adsorbents are needed for their removal from wastewaters. Carbon-doped magnesium oxide (C-MgO) and calcium carbonate (C-CaCO₃) were synthesized by the in situ hydrothermal treatment of Mg(OH)₂ and Ca(OH)₂ with carbon, and applied for the removal of eriochrome black T (EBT) at pH = 2.0 and uranium (U(VI)) at pH = 6.0. The Langmuir monolayer adsorption capacities of C-MgO (3.62 × 10^-4 mol/g for EBT and 8.10 × 10^-4 mol/g for U(VI)) were higher than those of C-CaCO₃ (2.53 × 10^-4 mol/g for EBT and 5.92 × 10^-4 mol/g for U(VI)). The high adsorption capacity of C-MgO was also evidenced with DFT calculations which showed that the sorption energies (ΔE) of C-MgO for EBT (20.62 kcal/mol) and U(VI) (63.41 kcal/mol) were higher than those of C-CaCO₃ for EBT (10.21 kcal/mol) and U(VI) (34.29 kcal/mol). In all cases, the electrostatic interactions were involved in the adsorption process. The sorption kinetic data followed pseudo-second-order kinetics. The results demonstrate that both C-MgO and C-CaCO₃ are reusable and can be effectively applied for the elimination of EBT and U(VI) from wastewater.

Facile one-pot solvothermal synthesis of magnetic mesoporous carbon for the efficient adsorption of methyl orange

A facile one-pot solvent thermal method was proposed to synthesize magnetic mesoporous carbon (MMC) using Fe(NO₃)₃·9H₂O as a precursor, Pluronic copolymer P123 as template, and chitosan as carbon source, and it was applied for the adsorptive remediation of methyl orange (MO). The characterization results of TEM, XRD, and IR showed that MMC consisted of graphitized carbon matrix and some black spherical particle mixture of Fe₃O₄ and Fe, and it was rich in hydroxyl and carbonyl groups. Besides, the effect of the content of Fe and the content of chitosan in MMC on the magnetism and adsorption performance of prepared material were investigated. In addition, the effects of pH value, initial concentration of methyl orange, and contact time on the adsorption performance of MO were studied, respectively. At 318 K, the maximum adsorption capacity of MO calculated from Langmuir isotherm was from 139 to 400 mg g^-1 on MMC. Kinetic studies demonstrated that the adsorption process obeyed a pseudo-second-order kinetic model. The regeneration experiments revealed that MMC could be reused at least five times without notable decrease of adsorption performance. These results illustrate that MMC is an efficient and economical adsorbent for the adsorption of MO.

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.

Design of Crosslinked Hydrogels Comprising Poly(Vinylphosphonic Acid) and Bis[2-(Methacryloyloxy)Ethyl] Phosphate as an Efficient Adsorbent for Wastewater Dye Removal

The development of adsorbents with high adsorption capacity and fast separation is of utmost importance for the environmental management of dye-bearing wastewaters. Within this scope, crosslinked hydrogels including poly(vinylphosphonic acid) (PVPA) and bis[2-(methacryloyloxy)ethyl] phosphate (BMEP) were designed with varying mole ratios of BMEP (5-40%). The Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) results revealed that the fabrication of crosslinked PVPA-BMEP hydrogels enhanced: (i) functionalities of PA groups in the structure of hydrogels, (ii) thermal stabilities up to 250 °C, and (iii) interaction between methylene blue (MB) molecules and hydrogels. The pseudo second-order kinetic model best described the experimental adsorption data. The behaviors of the isotherms were more appropriate for Langmuir than Freundlich isotherm for the experimental data. PVPA-BMEP (40%) hydrogel indicated a fast and an outstanding MB adsorption capacity of 2841 mg g-1, which has not been reported yet for polymer hydrogels, to the best of our knowledge. The thermodynamic studies concluded that MB adsorption process was spontaneous and exothermic in nature. The overall results suggest that the designed and fabricated PVPA-BMEP hydrogels have great potential for the efficient removal of coloring materials from wastewaters.

Design and identification of poly(vinyl chloride)/layered double hydroxide@MnO2 nanocomposite films and evaluation of the methyl orange uptake: linear and non-linear isotherm and kinetic adsorption models

In this work, an adsorbent based on poly(vinyl chloride) (PVC) for the removal of methyl orange (MO) dye is proposed.