Quartzite an efficient adsorbent for the removal of anionic and cationic dyes from aqueous solutions

Quartzite obtained from local source was investigated for the removal of anionic dye congo red (CR) and cationic dye malachite green (MG) as an adsorbent from aqueous solution in batch experiment. The adsorption process was studied as a function of dye concentration, contact time, pH and temperature. Adsorption process was described well by Langmuir and Freundlich isotherms. The adsorption capacity remained 666.7 mg/g for CR dye and 348.125 mg/g for MG dye. Data was analyzed thermodynamically, ΔH⁰ and ΔG⁰ values proved that adsorption of CR and MG is an endothermic and spontaneous process. Adsorption data fitted best in the pseudo-first order kinetic model. The adsorption data proved that quartzite exhibits the best adsorption capacity and can be utilized for the removal of anionic and cationic dyes.     

Adsorption characteristics of malachite green dye onto novel kappa-carrageenan-g-polyacrylic acid/TiO2–NH2 hydrogel nanocomposite

Batch adsorption experiments were carried out for the removal of malachite green (MG) cationic dye from aqueous solution using novel hydrogel nanocomposite that was prepared by graft copolymerization of acrylic acid (AA) onto kappa-carrageenan (κC) biopolymer in the presence of a crosslinking agent, a free radical initiator and aminosilica-functionalized TiO₂ nanoparticles (κC-g-PAA/TiO₂–NH₂). The factors influencing adsorption capacity of the adsorbents such as initial pH value (pH₀) of the dye solutions, TiO₂–NH₂ content (wt%), initial concentration of the dye, amount of adsorbents, and temperature were investigated. The adsorption capacity of hydrogel nanocomposite for MG was compared with hydrogel. The adsorption behaviors of both adsorbents showed that the adsorption kinetics and isotherms were in good agreement with a pseudo-second-order equation and the Langmuir equation. The high adsorption capacity (q _m= 666–833 (mg/g)) and the favorable heterogeneity factor (n = 1.2–1.5) calculated from isotherm equations show the efficiency of the novel adsorbents.     

Highly efficient removal of diazinon pesticide from aqueous solutions by using coconut shell-modified biochar

This study evaluates the adsorption of diazinon from aqueous solutions onto coconut shell-modified biochar using a batch system. The amount of dosage and initial pH are the main parameters being studied to obtain maximum adsorption capacity of the probe molecules. The carbonized coconut shell biochar (BC1), activated coconut shell biochar (BC2), chemically modified phosphoric acid (BC3) and sodium hydroxide coconut shell biochar (BC4) were prepared and tested as variables in the adsorption experiment. The characteristic of biochar via SEM, EDX and BET analysis revealed the large porous of surface morphology and slight changes in the composition with high surface area (405.97 – 508.07 m²/g) by following the sequence of BC3 > BC2 > BC4. Diazinon removal percentage as high as 98.96% was achieved at pH 7 with BC3 as adsorbent dosing at 5.0 g/L. The high coefficient of determination, R² with a small value of ERRSQ and χ² error analysis present the BC1 (0.9971) and BC2 (0.9999) are best fitted with Freundlich isotherm indicates multilayer sorption onto heterogeneous surface whereby the Langmuir isotherm model is the best fitting is described of monolayer adsorption process onto the homogenous surface of BC3 and BC4. The results indicated the maximum adsorption capacity (q_m) was achieved by BC3 with 10.33 mg/g, followed by BC2 (9.65 mg/g) in accordance to the Langmuir isotherm while Freundlich isotherm showed the highest adsorption capacity (k_F) with 1.73 mg/g (L/mg)^1/n followed by BC4 with 0.63 mg/g (L/mg)^1/n at favorable adsorption isotherm (1 ≤ n ≤ 10). Thus, the results obtained depicted that BC2 and BC3 are highly efficient adsorbents and both exhibit great potential in removing diazinon from aqueous solutions.     

Boron Removal from Aqueous Solutions by Adsorption on Waste Sepiolite and Activated Waste Sepiolite Using Full Factorial Design

In the present paper, boron removal from aqueous solution by adsorption was investigated and 2³ full factorial design was applied. Non activated waste sepiolite (NAWS) and HCl activated waste sepiolite (AWS) were used as adsorbents. Regression equation formulated for boron adsorption was represented as a function of response variables. The results obtained from the study on parameters showed that as pH increased and temperature decreased boron removal by adsorption increased. Adsorbed boron amount on AWS was higher than that of NAWS. Maximum boron removal was obtained at pH 10 and 20°C for both adsorbents. Adsorption data obtained from batch adsorption experiments carried out with NAWS and AWS fitted to the Langmuir equation. The batch adsorption capacities were found in mg/g: 96.15 and 178.57 for NAWS and AWS, respectively. The capacity value for column study was obtained by graphical integration as 219.01 mg/g for AWS. The Thomas and the Yoon-Nelson models were applied to experimental data to predict the breakthrough curves and to determine the characteristic parameters of the column useful for process design.     

Mixed phase Fe2O3/Mn3O4 magnetic nanocomposite for enhanced adsorption of methyl orange dye: Neural network modeling and response surface methodology optimization

In this research, a novel magnetic mesoporous adsorbent with mixed phase of Fe₂O₃/Mn₃O₄ nanocomposite was prepared by a facile precipitating method and characterized extensively. The prepared nanocomposite was used as adsorbent for toxic methyl orange (MO) dye removal from aqua matrix considering its high surface area (178.27 m²/g) with high saturation magnetization (23.07 emu/g). Maximum dye adsorption occurs at solution pH 2.0 and the electrostatic attraction between anionic form of MO dye molecules and the positively charged nanocomposite surface is the main driving force behind this adsorption. Response surface methodology (RSM) was used for optimizing the process variables and maximum MO removal of 97.67% is obtained at optimum experimental condition with contact time, adsorbent dose and initial MO dye concentration of 45 min, 0.87 g/l and 116 mg/l, respectively. Artificial neural network (ANN) model with optimum topology of 3–5–1 was developed for predicting the MO removal (%), which has shown higher predictive ability than RSM model. Maximum adsorption capacity of this nanocomposite was found to be 322.58 mg/g from Langmuir isotherm model. Kinetic studies reveal the applicability of second‐order kinetic model with contribution of intra‐particle diffusion in this process.     

Mechanistic insights into methylene blue removal via olive stone-activated carbon: A study on surface porosity and characterization

Global attention is increasingly focused on the adverse health and environmental impacts of textile dyes, marking the necessity for effective and sustainable dye remediation strategies in industrial wastewater. This study introduces a novel, eco-friendly activated carbon produced from olive stones (OLS), a readily available by-product of the olive oil industry. The OLS was chemically activated with H₃PO₄ and KOH, creating two materials: OLS-P and OLS-K, respectively. These were then utilized as cost-effective adsorbents for the removal of methylene blue (MB) dye. The activated materials were characterized via X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FTIR), iodine number, and pHpzc analysis, with the zero-point charge determined as approximately pH 1 for OLS-P and pH 8 for OLS-K. Batch adsorption experiments conducted at various temperatures revealed that adsorption process followed the pseudo-second-order kinetic model and the Langmuir isotherm model. Temperature was found to significantly impact adsorption performance, with OLS-K demonstrating a substantial increase in adsorption capacity (q_e) from 6.27 mg/g at 23˚C to 94.7 mg/g at 32 ˚C. Conversely, OLS-P displayed a decrease in q_e from 16.78 mg/g at 23 ˚C to 3.67 mg/g at 32 ˚C as temperature increased. The study highlights the potential of KOH-treated olive stones as a promising, cost-efficient adsorbent for methylene blue remediation from wastewater.     

Equilibrium,kinetic, and thermodynamic studies of lead ion adsorption from mine wastewater onto MoS2-clinoptilolite composite

This work explored the potential of clinoptilolite, molybdenum sulphide (MoS₂), and MoS₂-clinoptilolite composite in lead (Pb) removal from aqueous medium and industrial mining wastewater. MoS₂-clinoptilolite composite was successfully prepared by a hydrothermal method. The surface properties, structure, and composition of the synthesized composite and the parent compounds were analyzed by scanning electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectroscopy. The removal efficiency of lead from aqueous solution was studied in batch-mode experiments. The MoS₂-clinoptilolite was used for the removal of Pb ions (50 mg/L) from an aqueous solution: ~100% of the Pb was removed with a MoS₂-clinoptilolite dose of 0.075 g, pH 6 at 328K within 90 min. The adsorption capacities of Pb onto MoS₂-clinoptilolite were found to be higher than those onto clinoptilolite. Metal ion adsorption behavior was well explained by the Freundlich model, that is, multilayer adsorption of Pb molecules occurred on the heterogeneous surface of adsorbents in case of clinoptilolite, while in the case of MoS₂-clinoptilolite, the Langmuir model was suitable, that is, the adsorption occurred on a monolayer surface. The rate of Pb adsorption was explained by pseudo-second-order model suggesting that the adsorption process is presumably chemisorption. Thermodynamic parameters such as ΔH°, ΔS°, and ΔG° were calculated, which indicated that the adsorption was spontaneous and exothermic in nature. The selectivity of each adsorbent for Pb was also tested by adding the adsorbents to real gold mine water which contains competitive metal ions.     

Thermal analysis of growing media obtained from mixtures of paper mill waste materials and sewage sludge

This study deals with thermal analysis of growing media obtained from mixtures of paper will waste materials (one de-inking paper sludge, HP, and one reject from paper mill producing paper from virgin wood, RT) with sewage sludge. For the growing media formulation, one sewage sludge (L) was mixed with both paper mill waste materials at 10, 20, and 30% in volume. An incubation experiment was designed in order to study their carbon mineralization. Addition of sewage sludge significantly increases the carbon mineralization of growing media based on RT. In case of HP, carbon mineralization increases after addition of sewage sludge in 30% (HP + 30L treatment). Thermogravimetric analysis (TG and DTG) of growing media was performed before and after incubation experiment in order to study the organic matter transformation. The higher the carbon mineralization, the greater the difference between TG curves of samples before and after the incubation. The WL₃/WL₂ ratio increases after incubation of samples as a result of organic matter stabilisation. For HP growing media, the highest value corresponds to HP + 30L whereas HP + 20L, and HP + 10L show similar values. In case of RT, the WL₃/WL₂ index shows a progressive increase with sewage sludge content.     

Preparation of ferric nitrate–graphene nanocomposite and its adsorption of arsenic(V) from simulated arsenic‐containing wastewater

Ferric nitrate–graphene (FG) nanocomposites synthesized via the equivalent‐volume impregnation method were used for the removal of As(V) species from simulated arsenic‐containing wastewater. Effects of various factors were assessed, such as the reaction temperature, solution pH, adsorbent dosage, and reaction time. The results indicated that the As(V) removal efficiency was as high as 99%, and the concentration of arsenic‐containing wastewater after FG treatment was as low as 9.4 μg L^–1 as a result of the optimal absorption capacity and maximum specific surface area (171.766 m²/g) of this material. The equilibrium adsorption capacity of FG for As(V) was achieved in approximately 20 min, and the maximum adsorption capacity was calculated to be 112.4 mg g^–1 by Langmuir adsorption isotherm, which was higher than that of other adsorbents such as manganese‐incorporated iron(III) oxide–graphene (14.42 mg g^–1). Moreover, the removal efficiency of As(V) can be maintained above 95% under acidic and alkaline conditions. Brunauer–Emmett–Teller analysis showed that the modified FG pore structure was regular. Based on the characterizations by X‐ray diffraction, X‐ray photoelectron spectroscopy, and Fourier transform infrared, the products on the surface of the used FG were Fe(OH)₃, FeAsO₄, and other compounds, and As(V) was mainly removed by the formation of insoluble compounds and coprecipitation.     

Novel Fe3O4/hydroxyapatite/β‐cyclodextrin nanocomposite adsorbent: Synthesis and application in heavy metal removal from aqueous solution

The increased global concern on environmental protection has made researchers focus their attention on new and more efficient methods of pollutant removal. In this research, novel nanocomposite adsorbents,i.e., magnetic hydroxyapatite (Fe₃O₄@HA) and magnetic hydroxyapatite β‐cyclodextrin (Fe₃O₄@HA‐CD) were synthesized and used for heavy metal removal. The adsorbents were characterized by FTIR, XRD, TGA, VSM, and SEM. In order to investigate the effect of β‐cyclodextrin (β‐CD) removal efficiency, adsorption results of nine metal ions were compared for both adsorbents. β‐CD showed the most increasing effect for Cd²⁺ and Cu²⁺ removal, so these two ions were selected for further studies. The effect of diverse parameters including pH, contact time, initial metal ion concentration and adsorbent dosage on the adsorption process was discussed. The optimum pH was 6 and adsorption equilibrium was achieved after 1 hr. Adsorption kinetic data were well fitted by pseudo‐second‐order model proposing that metal ions were adsorbed via chemical reaction. Adsorption isotherm was best described by the Langmuir model, and maximum adsorption capacity for Cd²⁺ and Cu²⁺ was 100.00 and 66.66 (mg/g), respectively. Desorption experiment was also done, and the most efficient eluent used for desorption of metal ions was EDTA (0.001 M) with 91% and 88% of Cd²⁺ and Cu²⁺ release, respectively. Recyclability studies also showed a 19% decrease in the adsorption capacity of the adsorbent after five cycles of regeneration. Therefore, the synthesized adsorbents were recognized as potential candidates for heavy metal adsorption applications.     

Preparation and characterization of nanocomposite,silica aerogel,activated carbon and its adsorption properties for Cd (II) ions from aqueous solution

A novel composite adsorbent, silica aerogel activated carbon was synthesized by sol-gel process at ambient pressure drying method. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Nitrogen adsorption/desorption isotherms (BET).In the present study, the mentioned adsorbent was used moderately for the removal of cadmium ions from aqueous solutions and was compared with two other adsorbents of cadmium, activated carbon and silica aerogel. The experiments of Cd adsorption by adsorbents were performed at different initial ion concentrations, pH of the solution, adsorption temperature, adsorbent dosage and contact time. Moreover, the optimum pH for the adsorption was found to be 6.0 with the corresponding adsorbent dosage level of 0.1 g at 60 °C temperature. Subsequently, the equilibrium was achieved for Cd with 120 min of contact time.Consequently, the results show that using this composite adsorbent could remove more than 60% of Cd under optimum experimental conditions. Langmuir and Freundlich isotherm model was applied to analyze the data, in which the adsorption equilibrium data were correlated well with the Freundlich isotherm model and the equilibrium adsorption capacity (q_e) was found to be 0.384 mg/g in the 3 mg/L solution of cadmium.     

Biosorption of lead from aqueous solution by seed powder of Strychnos potatorum L.

In the present study, Pb(II) removal efficiency of Strychnos potatorum seed powder (SPSP) from aqueous solution has been investigated. Batch mode adsorption experiments have been conducted by varying pH, contact time, adsorbent dose and Pb(II) concentration. Pb(II) removal was pH dependent and found to be maximum at pH 5.0. The maximum removal of Pb(II) was achieved within 360 min. The Lagergren first-order model was less applicable than pseudo-second-order reaction model. The equilibrium adsorption data was fitted to Langmuir and Freundlich adsorption isotherm models to evaluate the model parameters. Both models represented the experimental data satisfactorily. The monolayer adsorption capacities of SPSP as obtained from Langmuir isotherm was found to be 16.420 mg/g. The FTIR study revealed the presence of various functional groups which are responsible for the adsorption process.     

Preparation and application of magnetic molecularly imprinted polymers for the isolation of chelerythrine from Macleaya cordata

A novel type of magnetic molecularly imprinted polymer was prepared for the selective enrichment and isolation of chelerythrine from Macleaya cordata (Willd) R. Br. The magnetic molecularly imprinted polymers were prepared using functional Fe₃O₄@SiO₂ as a magnetic support, chelerythrine as template, methacrylic acid as functional monomer, and ethylene glycol dimethacrylate as cross‐linker. Density functional theory at the B3LYP/6‐31G (d, p) level with Gaussian 09 software was applied to calculate the interaction energies of chelerythrine, methacrylic acid and the complexes formed from chelerythrine and methacrylic acid in different ratios. The structural features and morphology of the synthesized polymers were characterized by using Fourier transform infrared spectroscopy, X‐ray diffraction, transmission electron microscopy, and vibration sample magnetometry. Adsorption experiments revealed that the magnetic molecularly imprinted polymers possessed rapid kinetics, high selectivity, and a higher binding capacity (7.96 mg/g) to chelerythrine than magnetic molecularly non‐imprinted polymers (2.36 mg/g). The adsorption process was in good agreement with the Langmuir adsorption isotherm and pseudo‐second‐order kinetics models. Furthermore, the magnetic molecularly imprinted polymers were successfully employed as adsorbents for the extraction and enrichment of chelerythrine from Macleaya cordata (Willd) R. Br. The results indicated that the magnetic molecularly imprinted polymers were suitable for the selective adsorption of chelerythrine from complex samples such as natural medical plants.     

Removal of chromium from water using pea waste – a green approach

Abstract

Agro-waste materials have carboxylic and phenolic groups that play the main role in metal adsorption. The advantages of these materials include easy availability, low cost, and reasonable metal removal capacity. One of the materials (usually considered as waste) is pea waste (pods). Present work comprises adsorption of chromium from aqueous solution using powder of pods of garden peas (Pisum sativum) in batch. Important parameters like adsorbent dose, pH, contact time, and agitation speed were studied. Adsorption equilibrium was explained by Langmuir, Freundlich, and Temkin isotherms. Maximum chromium uptake (q _m) was 3.56 mg/g of adsorbent. Heat of adsorption, as evaluated by Temkin isotherm was 1.96 kJ/mol. It is proposed that pea pods can be an effective and environmentally benign (green) adsorbents for removal of chromium from industrial effluents and waste waters.     

Magnetic Fe3O4/ZIF-8 optimization by Box-Behnken design and its Cd(II)-adsorption properties and mechanism

In this study, the preparation of magnetic Fe₃O₄/ZIF-8 (MFZ) and its adsorption properties for Cd(II) from water were investigated. Various characterizations demonstrate that the as-prepared MFZ has well magnetic-separation performance and thermal stability. In batch adsorption tests, the effects of pH, initial concentration, and adsorbent dosage were evaluated. According to the findings, when the pH is 7 and the dosage is 150 mg/L, the adsorption capacity for a 40 mg/L Cd(II) solution reaches 102.3 mg/g in 180 min. The Cd(II) adsorption processes was found to correspond to pseudo-first-order kinetics and Langmuir model according to the adsorption kinetics and isotherms. The Langmuir model predicted a maximal saturation adsorption capacity of 160.26 mg/g at 298 K. Thermodynamic analysis revealed that the Cd(II) adsorption is an endothermic, spontaneous process. Ion exchange, coordination reaction, and electrostatic interaction are all involved in Cd(II) adsorption by MFZ. The optimum conditions for Cd(II) adsorption were proposed and confirmed in accordance with the results of the response surface optimization experiments. Furthermore, regeneration tests demonstrate the great repeated regeneration ability of MFZ. According to the anticipated production cost, treating wastewater with a Cd(II) concentration of 40 mg/L would cost roughly US$ 8.35/m³. MFZ showed good potential for Cd(II) removal from water.     

Lipase bound cellulose nanofibrous membrane via Cibacron Blue F3GA affinity ligand

Cellulose (Cell) nanofibrous membranes were prepared by nucleophilic reaction of the cellulose hydroxyl with the triazinyl chloride of Cibacron Blue F3GA (CB) ligand and studied as affinity membranes for lipase enzyme. Cell nanofibrous membranes containing fibers with 200 nm average diameters were prepared by electrospinning of cellulose acetate (CA), followed by alkaline hydrolysis. The CB capacity of the Cell nanofibrous membranes was optimized by lengthening the nucleophilic reaction time and increasing CB concentration and ionic strength. The equilibrium adsorption isotherms of CB on the Cell nanofibrous membranes followed a typical Langmuir monolayer adsorption behavior. At 242 mg CB/g of Cell, the maximum lipase adsorption capacity (q_m) and the dissociation constant (K_d) values were 41.02 mg/g and 0.25 mg/mL, respectively. Optimal lipase adsorption capacity was obtained at pH 4.0, its isoelectric point, with added NaCl on Cell membranes 86 mg CB capacity per g of Cell. A facile lipase loading capacity of 16.21 mg/g of CB–Cell was achieved under moderated conditions and could be optimized to reach at least 150 mg/g. The CB–Cell bound lipase had similar catalytic rate and retained 86.2% activity as in its free form. These findings clearly show that the CB bound Cell nanofibrous membrane is a highly efficient ultra-high specific porous support for lipase enzyme and is potentially versatile for immobilizing other enzymes and as affinity membrane for proteins.     

Enhanced adsorption of radioactive strontium ions from aqueous solution by H2O2-modified attapulgite

Effective adsorption of Sr(II) onto H₂O₂-modified attapulgite in aqueous solution was investigated about kinetics and isothermal equilibrium adsorption. The adsorption equilibrium process of Sr(II) on adsorbents reached about 8 h at 40 °C. The adsorption kinetics followed the pseudo-second order equation and the isothermal adsorption data were fit well with the Langmuir isotherm model. The enhanced adsorption mechanism of H₂O₂-modified attapulgite for Sr(II) in aqueous solution was expatiated in detail. The H₂O₂ treatment for attapulgite is effective and as-made adsorbents can be applied for removal of Sr(II) in radioactive waste water.

     

Efficient removal of MB dye using litchi leaves powder adsorbent: Isotherm and kinetic studies

Removal of Methylene Blue (MB) dye using Litchi Leaves Powder (LLP) material was carried out in batch mode. Effect of the mass of the adsorbent (0.1–2.5 g/L), pH of the solution (2−12), starting concentration of MB dye (50–150 mg/L), ionic strength using NaCl (0.1–0.5 M) as an electrolyte, contact time (0–60 min) on the adsorption of MB dye was studied. To calculate pH at which LLP material surface becomes neutral point of zero charge (pH_pzc) is also determined and found to be 6.48. Removal process best fit in the pseudo-second-order kinetic model as indicated by its higher R² value (0.999). Isotherm models (Freundlich and Langmuir) were fitted to the data obtained from the experiment to understand the adsorption behaviour. Result shows that experimental data were fitted to the both isotherm models (Freundlich and Langmuir) as indicated by higher R² value for both Freundlich (0.991) and Langmuir (0.994) model, and it was determined that LLP has a maximum adsorption capacity of 119.76 mg/g.     

Synthesis of nano‐sized magnetite mesoporous carbon for removal of Reactive Yellow dye from aqueous solutions

In this study, core‐shell structures of magnetite nanoparticles coated with CMK‐8 ordered mesoporous carbon (Fe₃O₄@SiO₂‐CMK‐8 NPs) have been successfully synthesized for the first time by carbonizing sucrose inside the pores of the Kit‐6 mesoporous silica. The nano‐sized mesoporous particles were characterized by X‐ray diffraction, Fourier transform‐infrared spectroscopy, scanning electron microscope, dynamic light scattering, vibrating‐sample magnetometer, Brunauer–Emmett–Teller (BET) and transmission electron microscopy instruments. The obtained nanocomposite was used for removal of Reactive Yellow 160 (RY 160) dye from aqueous samples. The N₂ adsorption–desorption method (at 77 K) confirmed the mesoporous structure of synthesized Fe₃O₄@SiO₂‐CMK‐8 NPs. Also, the surface area was calculated by the BET method and Langmuir plot as 276.84 m²/g and 352.32 m²/g, respectively. The surface area, volume and pore diameter of synthesized nanoparticles (NPs) were calculated from the pore size distribution curves using the Barrett–Joyner–Halenda formula (BJH). To obtain the optimum experimental variables, the effect of various experimental parameters on the dye removal efficiency was studied using Taguchi orthogonal array experimental design method. According to the experimental results, about 90.0% of RY 160 was removed from aqueous solutions at the adsorbent amount of 0.06 g, pH 3 and ionic strength = 0.05 m during 10 min. The pseudo‐second order kinetic model provided a very good fit for the RY 160 dye removal (R² = 0.999). The Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models were applied to describe the equilibrium isotherms, and the Langmuir isotherm showed the best fit to data with the maximum adsorption capacity of 62.893 mg/g. Furthermore, the Fe₃O₄@SiO₂‐CMK‐8 NPs could be simply recovered by external magnet, and exhibited recyclability and reusability for a subsequent six runs.