Removal of Chromium(III) and Cadmium(II) Heavy Metal Ions from Aqueous Solutions Using Treated Date Seeds: An Eco-Friendly Method

The aim of the research was to prepare low-cost adsorbents, including raw date pits and chemically treated date pits, and to apply these materials to investigate the adsorption behavior of Cr(III) and Cd(II) ions from wastewater. The prepared materials were characterized using SEM, FT-IR and BET surface analysis techniques for investigating the surface morphology, particle size, pore size and surface functionalities of the materials. A series of adsorption processes was conducted in a batch system and optimized by investigating various parameters such as solution pH, contact time, initial metal concentrations and adsorbent dosage. The optimum pH for achieving maximum adsorption capacity was found to be approximately 7.8. The determination of metal ions was conducted using atomic adsorption spectrometry. The experimental results were fitted using isotherm Langmuir and Freundlich equations, and maximum monolayer adsorption capacities for Cr(III) and Cd(II) at 323 K were 1428.5 and 1302.0 mg/g (treated majdool date pits adsorbent) and 1228.5 and 1182.0 mg/g (treated sagai date pits adsorbent), respectively. It was found that the adsorption capacity of H₂O₂-treated date pits was higher than that of untreated DP. Recovery studies showed maximal metal elution with 0.1 M HCl for all the adsorbents. An 83.3–88.2% and 81.8–86.8% drop in Cr(III) and Cd(II) adsorption, respectively, were found after the five regeneration cycles. The results showed that the Langmuir model gave slightly better results than the Freundlich model for the untreated and treated date pits. Hence, the results demonstrated that the prepared materials could be a low-cost and eco-friendly choice for the remediation of Cr(III) and Cd(II) contaminants from an aqueous solution.     

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.     

Removal of cadmium(II) and zinc(II) metal ions from binary aqueous solution by rice husk ash

The present study reports the competitive adsorptive removal of cadmium (Cd(II)) and zinc (Zn(II)) ions from binary systems using rice husk ash (RHA), a waste obtained from the rice husk-fired furnaces, as an adsorbent. The initial pH (pH₀) affects significantly the capacity of RHA for adsorbing the metallic ions in the aqueous solution. The pH₀ ≈ 6.0 is found to be the optimum for the removal of Cd(II) and Zn(II) ions by RHA. The single ion equilibrium adsorption from the binary solution is better represented by the non-competitive Redlich–Peterson (R–P) and the Freundlich models than by Langmuir model in the initial metal concentration range of 10–100 mg/l. The adsorption of Zn(II) ion is more than that of Cd(II) ion, and this trend is in agreement with the single-component adsorption data. The equilibrium metal removal decreases with increasing concentrations of the other metal ion and the combined effect of Cd(II) and Zn(II) ions on RHA is generally found to be antagonistic. Non-modified Langmuir, modified Langmuir, extended-Langmuir, extended-Freundlich, Sheindorf–Rebuhn–Sheintuch (SRS), non-modified R–P and modified R–P adsorption models were tested to find the most appropriate competitive adsorption isotherm for the binary adsorption of Cd(II) and Zn(II) ions onto RHA by minimizing the Marquardt's percent standard deviation (MPSD) error function. The extended-Freundlich model satisfactorily represents the adsorption equilibrium data of Cd(II) and Zn(II) ions onto RHA.     

Post Synthetic Modification of NH2-(Zr-MOF) via Rapid Microwave-promoted Synthesis for Effective Adsorption of Pb(II) and Cd(II)

Excessive heavy metals in the water constitute a health hazard to humans, yet it may be efficiently purified using adsorbents. Herein, for the first time, UiO-66-NH₂ was modified by Glycidyl methacrylate (GMA) via microwave heating method to investigate its potential for adsorption of Pb(II) and Cd(II) metal ions. Synthesized MOF was characterized by TGA, XRD, BET, FE-SEM-EDX, and FTIR. The MOF has a huge surface area of 1144 m²/g, a mean pore diameter of 2.84 nm, and a total pore volume of 0.37 cm³/g. The effect of UiO-66-GMA performance was evaluated by investigating the impact of pH (1–9), contact time (0–200 min), initial metal ions concentration (20–1000 mg/L), temperature (25–55 °C), adsorbent dosage (0.5–3 g/L), and co existences of other metals was investigated on Pb(II) and Cd(II) percentage removal. Following an analysis of the adsorption isotherms, kinetics, and thermodynamics, the Temkin isothermal model showed an excellent fit with the adsorption data (R² = 0.99). The adsorption process was a spontaneous endothermic reaction and kinetically followed the pseudo-second-order kinetics model. Microwave heating method produced highly crystalline small Zr-MOF nanoparticles with a short reaction time. It promoted the simple yet highly efficient synthesis of Zr-based MOFs, as shown by the reaction mass space-time yield. The adsorption capability of Pb to the presence of several polar functional groups, including as primary and secondary amines, ester, alkene, and hydroxyl groups. This adsorbent is a potential candidate for wastewater treatment due to its outstanding structural stability in acidic and basic solutions, high removal efficiency, and recyclability.     

Adsorptive Removal of Cd,Cu, Ni and Mn from Environmental Samples Using Fe3O4-Zro2@APS Nanocomposite: Kinetic and Equilibrium Isotherm Studies

In this study, Fe₃O₄-ZrO₂ functionalized with 3-aminopropyltriethoxysilane (Fe₃O₄-ZrO₂@APS) nanocomposite was investigated as a nanoadsorbent for the removal of Cd(II), Cu(II), Mn (II) and Ni(II) ions from aqueous solution and real samples in batch mode systems. The prepared magnetic nanomaterials were characterized using X-ray powder diffraction (XRD), scanning electron microscopy/energy dispersion x-ray (SEM/EDX) Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Factors (such as adsorbent dose and sample pH) affecting the adsorption behavior of the removal process were studied using the response surface methodology. Under optimized condition, equilibrium data obtained were fitted into the Langmuir and Freundlich isotherms and the data fitted well with Langmuir isotherms. Langmuir adsorption capacities (mg/g) were found to be 113, 111, 128, and 123 mg/g for Cd, Cu, Ni and Mn, respectively. In addition, the adsorption kinetics was analyzed using five kinetic models, pseudo-first order, pseudo-second order, intraparticle diffusion and Boyd models. The adsorbent was successfully applied for removal of Cd(II), Cu(II), Mn (II) and Ni(II) ions in wastewater samples.     

Adsorption of Cd(II) Ions onto Activated Carbon Prepared from Hazelnut Husks

In this study, a batch adsorption of Cd(II) ions onto activated carbon (AC) produced from hazelnut husks were investigated. The factors controlling the adsorption process such as initial pH, agitation time, dosage and initial concentration have been examined. The AC was showed a high affinity to Cd(II) ions at pH values between 5.0 and 7.0. The equilibrium time was found to be 300 minutes. Cd(II) adsorption equilibrium was analyzed with both Langmuir and Freundlich isotherm equations and it was found that Langmuir equations fitted well with the experimental data. Maximum Cd(II) adsorption capacity of AC was calculated to be 20.9 mg g^?1. Cd(II) adsorption kinetics described well with the pseudo second order model. The activated carbon prepared from hazelnut husks is efficient sorbent material for the removal of Cd(II) ions from aqueous solutions.     

Poly-L-Histidine Attached Poly(glycidyl methacrylate) Cryogels for Heavy Metal Removal

Poly-L-histidine immobilized poly(glycidyl methacrylate) (PGMA) cryogel discs were used for the removal of heavy metal ions [Pb(II), Cd(II), Zn(II) and Cu(II)] from aqueous solutions. In the first step, PGMA cryogel discs were synthesized using glycidyl methacrylate (GMA) as a basic monomer and methylene bisacrylamide (MBAAm) as a cross linker in order to introduce active epoxy groups through the polymeric backbone. Then, the metal chelating groups are incorporated to cryogel discs by immobilizing poly-L-histidine (mol wt ≥ 5000) having poly-imidazole ring. The swelling test, fourier transform infrared spectroscopy and scanning electron microscopy were performed to characterize both the PGMA and poly-L-histidine immobilized PGMA [P-His@PGMA] cryogel discs. The effects of the metal ion concentration and pH on the adsorption capacity were studied. These parameters were varied between 3.0–6.0 and 10–800 mg/L for pH and metal ion concentration, respectively. The maximum adsorption capacity of heavy metal ions of P-His@PGMA cryogel discs were 6.9 mg/g for Pb(II), 6.4 mg/g for Cd(II), 5.6 mg/g for Cu(II) and 4.3 mg/g for > Zn(II). Desorption of heavy metal ions was studied with 0.1 M HNO₃ solution. It was observed that cryogel discs could be recurrently used without important loss in the adsorption amount after five repetitive adsorption/desorption processes. Adsorption isotherms were fitted to Langmuir model and adsorption kinetics were suited to pseudo-second order model. Thermodynamic parameters (i.e. ΔH° ΔS°, ΔG°) were also calculated at different temperatures.     

Adsorption of antimony using amino-functionalized magnetic MIL-101(Cr): Optimization by response surface methodology

Amino-functionalized magnetic MIL-101(Cr) was prepared via a one-step solvothermal method, characterized, and applied in adsorptive Sb(III) removal. The effects of solution pH, adsorbent dosage, and coexisting substances on the adsorption of Sb(III) by MIL-101(Cr)–NH₂/MnFe₂O₄ were studied. The adsorption kinetics were analyzed using pseudo-first order, pseudo-second order, intraparticle diffusion, and Elovich models, while Freundlich and Langmuir isotherm models were used to fit the experimental data. The pseudo-second-order kinetic model provided the best fit for the kinetic data. The maximum adsorption capacity of MIL-101(Cr)–NH₂/MnFe₂O₄ for Sb(III) was 91.07 ​mg/g, as calculated using the Langmuir adsorption isotherm model. Thermodynamic analysis revealed that the adsorption of antimony onto MIL-101(Cr)–NH₂/MnFe₂O₄ is spontaneous and endothermic, while response surface optimization revealed that the optimal conditions for Sb(III) adsorption by MIL-101(Cr)–NH₂/MnFe₂O₄ are an adsorbent loading of 222.55 ​mg/L, a pH of 4.5, and a temperature of 294.59 ​K. The predicted adsorption capacity of MIL-101(Cr)–NH₂/MnFe₂O₄ for Sb(III) is only a 1.8% deviation from the actual value. Furthermore, MIL-101(Cr)–NH₂/MnFe₂O₄ exhibits strong magnetism, allowing it to be separated from wastewater using a magnet. Finally, a preliminary economic analysis showed that the cost of treating a ton wastewater containing 25 ​mg/L antimony using this composite would be 26.24 USD. Thus, MIL-101(Cr)–NH₂/MnFe₂O₄ is promising for treatment of Sb(III)-containing wastewater.     

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.     

Adsorption of Ni(II), Cu(II) and Cd(II) from aqueous solutions by amino modified nanostructured microfibrillated cellulose

The aim of the present study was to investigate the adsorption properties of aminopropyltriethoxysilane (APS) modified microfibrillated cellulose (MFC) in aqueous solutions containing Ni(II), Cu(II) and Cd(II) ions. The modified adsorbents were characterized using elemental analysis, Fourier transform infrared spectroscopy, SEM and zeta potential analysis. The adsorption and regeneration studies were conducted in batch mode using various different pH values and contact times. The maximum removal capacities of the APS/MFC adsorbent for Ni(II), Cu(II), and Cd(II) ions were 2.734, 3.150 and 4.195 mmol/g, respectively. The Langmuir, Sips and Dubinin-Radushkevich models were representative to simulate adsorption isotherms. The adsorption kinetics of Ni(II) Cu(II), and Cd(II) adsorption by APS/MFC data were modeled using the pseudo-first-order, pseudo-second-order and intra-particle diffusion kinetics equations. The results indicate that the pseudo-second-order kinetic equation and intra-particle diffusion model were adequate to describe the adsorption kinetics.     

Kinetics and equilibrium adsorption of Cu(II), Cd(II), and Ni(II) ions by chitosan functionalized with 2[-bis-(pyridylmethyl)aminomethyl]-4-methyl-6-formylphenol

Chitosan biopolymer chemically modified with the complexation agent 2[-bis-(pyridylmethyl)aminomethyl]-4-methyl-6-formylphenol (BPMAMF) was employed to study the kinetics and the equilibrium adsorption of Cu(II), Cd(II), and Ni(II) metal ions as functions of the pH solution. The maximum adsorption of Cu(II) was found at pH 6.0, while the Cd(II) and Ni(II) maximum adsorption occurred in acidic media, at pH 2.0 and 3.0, respectively. The kinetics was evaluated utilizing the pseudo-first-order and pseudo-second-order equation models and the equilibrium data were analyzed by Langmuir and Freundlich isotherms models. The adsorption kinetics follows the mechanism of the pseudo-second-order equation for all studied systems and this mechanism suggests that the adsorption rate of metal ions by CHS-BPMAMF depends on the number of ions on the adsorbent surface, as well as on their number at equilibrium. The best interpretation for the equilibrium data was given by the Langmuir isotherm and the maximum adsorption capacities were 109 mg g-1 for Cu(II), 38.5 mg g-1 for Cd(II), and 9.6 mg g-1 for Ni(II). The obtained results show that chitosan modified with BPMAMF ligand presented higher adsorption capacity for Cu(II) in all studied pH ranges.     

Equilibrium,kinetic and thermodynamic biosorption studies of Hg(II) on red algal biomass of Porphyridium cruentum

Among a variety of microbial materials employed for biosorption, algae have added advantages of non-toxic and autotrophic nature. In this study, biosorption of Hg(II) was studied with red algal biomass of Porphyridium cruentum. The parameters affecting biosorption such as dosage of biosorbent, pH, contact time, initial metal concentration, temperature and effect of foreign metal cations in binary system were evaluated. Kinetic data were described with the help of pseudo-first-order and pseudo-second-order kinetic models. Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models were applied to adsorption equilibrium data. According to the results, the maximum removal capacity (q_max) was 2.62?mg/g observed at pH 7 with 0.25?g/L of biosorbent dosage for Hg(II) solution containing 10?mg/L of metal ions. The Langmuir isotherm model fits best to the adsorption data while the kinetic data followed the pseudo-second-order model. Thermodynamics studies showed that the biosorption process of Hg(II) on P. cruentum was exothermic in nature.     

Removal of Cd(II) from Micro-Polluted Water by Magnetic Core-Shell Fe3O4@Prussian Blue

A novel core-shell magnetic Prussian blue-coated Fe₃O₄ composites (Fe₃O₄@PB) were designed and synthesized by in-situ replication and controlled etching of iron oxide (Fe₃O₄) to eliminate Cd (II) from micro-polluted water. The core-shell structure was confirmed by TEM, and the composites were characterized by XRD and FTIR. The pore diameter distribution from BET measurement revealed the micropore-dominated structure of Fe₃O₄@PB. The effects of adsorbents dosage, pH, and co-existing ions were investigated. Batch results revealed that the Cd (II) adsorption was very fast initially and reached equilibrium after 4 h. A pH of 6 was favorable for Cd (II) adsorption on Fe₃O₄@PB. The adsorption rate reached 98.78% at an initial Cd (II) concentration of 100 μg/L. The adsorption kinetics indicated that the pseudo-first-order and Elovich models could best describe the Cd (II) adsorption onto Fe₃O₄@PB, indicating that the sorption of Cd (II) ions on the binding sites of Fe₃O₄@PB was the main rate-limiting step of adsorption. The adsorption isotherm well fitted the Freundlich model with a maximum capacity of 9.25 mg·g⁻¹ of Cd (II). The adsorption of Cd (II) on the Fe₃O₄@PB was affected by co-existing ions, including Cu (II), Ni (II), and Zn (II), due to the competitive effect of the co-adsorption of Cd (II) with other co-existing ions.     

Fabrication and optimization calix[8]arene-PbS nanoadsorbents for the adsorption of methylene blue: Isotherms,kinetics and thermodynamics studies

The present study aims to determine the adsorption behaviour of methylene blue (MB) dye based on calix[8]arene-modified lead sulphide (PbS) nanoadsorbents under optimal conditions. Response surface methodology (RSM) was executed to evaluate the interactive effect of three factors (adsorbent dosage, contact time, and pH) on the adsorption of MB dye using a central composite design (CCD). The optimised values for adsorbent dosage, contact time, and pH solution were found to be 45.00 mg of calix[8]arene-modified PbS, contact time of 180 min, and pH 6. This study reports the results of batch adsorption experiments, which include the adsorption capacity, kinetics, and isotherm of the MB adsorption process. Pseudo-first order and pseudo-second order were demonstrated for their quality to fit the data. Pseudo-second order was the best in fitting the adsorption data with the higher R² values (R² > 0.928), indicating chemisorption to be the mechanism of adsorption. The Langmuir and Freundlich equilibrium models were employed to determine the isotherm parameters. The equilibrium assessment illustrated that the Langmuir isotherm model fitted well with the adsorption data, and a maximum MB adsorption capacity of 11.90 mg/g was achieved. The characterisation studies with EDX, FESEM, and FTIR indicated a successful synthesis of calix[8]arene-modified PbS.     

Removal of Cd(II) and Pb(II) from aqueous solution by modified attapulgite clay

Three low-cost adsorbents (purified raw attapulgite (A-ATP), high-temperature-calcined attapulgite (T-ATP), and hydrothermal loading of MgO (MgO-ATP)) were prepared as adsorbents for the removal of Cd(II) and Pb(II). By evaluating the effect of the initial solution pH, contact time, initial solution concentration, temperature and coexistence of metal ions on Cd(II) and Pb(II) adsorption, the experimental results showed that MgO-ATP was successfully prepared by hydrothermal reaction and calcination as well as appearing to be a promising excellent adsorbent. At an initial pH of 5.0, A-ATP, T-ATP and MgO-ATP reached maximum adsorption amounts of 43.5, 53.9 and 127.6 mg/g for Pb(II) and 10.9, 11.2, and 25.3 mg/g for Cd(II) at 298 K, respectively. The Cd(II) adsorption on A-ATP was fitted by the Freundlich model, while the adsorption of Pb(II) and Cd(II) on T-ATP and MgO-ATP as well as Pb(II) adsorption on A-ATP agreed with the Langmuir model. All kinetic experimental data favored pseudo second-order model. The calculated thermodynamic parameters suggested that Pb(II) adsorption onto MgO-ATP was spontaneous and exothermic. When considering foreign metal ions, the three adsorbents all presented preferential adsorption for Pb (II). Chemical adsorption had a high contribution to the removal of Cd(II) and Pb(II) by modified attapulgite. In summary, the adsorption was greatly enhanced by the hydrothermal loading of MgO. It aimed to provide insights into the MgO-ATP, which could be able to efficiently remove Cd(II) and Pb(II) and serve as an economic and promising adsorbent for heavy metal-contaminated environmental remediation.     

Adsorptive scavenging of cationic dyes from aquatic phase by H3PO4 activated Indian jujube (Ziziphus mauritiana) seeds based activated carbon: Isotherm,kinetics, and thermodynamic study

In the present work, a cost-effective Indian jujube seeds derived activated carbon (IJSAC) prepared via o-phosphoric acid chemical activation, is studied for the sequestration of acriflavine (AF) and Victoria blue B (VB) from the aquatic environment. The activated carbon is characterized by Fourier transform infrared spectroscopy, N₂-adsorption/desorption isotherm, scanning electron microscopy techniques and point of zero-charge measurement. The specific surface area (S_BET) of 571 m²/g with a pore radius of 22.45 Å specifies mesoporous nature of the IJSAC. The implication of operational conditions on the adsorption of both dyes onto IJSAC assessed by batch methodology, establish the optimal conditions as dosage (1.5 and 2.5 g/L), contact time (60 min), pH (8 and 10), and initial concentration (130 and 140 mg/L) for AF and VB uptake, respectively. The Freundlich adsorption isotherm model (R² = 0.99) appropriates the equilibrium data suggesting multilayer adsorption onto heterogeneous surface sites, while pseudo-second order (R² = 0.95–0.99) is the best fit kinetic model. The liquid film and intraparticle diffusion modelling demonstrate that the adsorption process of these dyes is governed by both the steps. Maximum Langmuir adsorption capacity is 113.6 mg/g for acriflavine and 92.78 mg/g for Victoria blue B. Thermodynamic studies indicate endothermic and spontaneous adsorption of dyes. The adsorption mechanism for the uptake of AF and VB by IJSAC most probably involves hydrogen bonding, electrostatic and π-π interactions. Based on its high adsorption capacity, relatively faster kinetics, and reusability, IJSAC can be perceived as a proficient and effective adsorbent for cationic dyes removal from the liquid waste.     

Fabrication of SiO2/CuFe2O4/polyaniline composite: A highly efficient adsorbent for heavy metals removal from aquatic environment

A novel multifunctional of SiO₂/CuFe₂O₄/polyaniline composite was synthesized through the interaction between silica (SiO₂), copper iron oxide (CuFe₂O₄), and polyaniline (PANI) as starting materials. SiO₂/CuFe₂O₄/polyaniline composite was characterized for morphology, crystallinity, textural properties, and utilised for the removal of Fe(II), Mn(II), and Cu(II) from synthetic wastewater solutions. The roles of solution pH (2.0–6.0), interaction time (15–420 min), initial ion concentration (50–700 mg/L), and solution temperature (30–50 °C) in the adsorption process were investigated. The adsorption capacities of SiO₂/CuFe₂O₄/PANI for the tested metal ions were high compared to SiO₂, CuFe₂O_4, and polyaniline. Equilibrium studies indicated that Fe(II) and Mn(II) adsorption were compliant with the Langmuir model, while the Freundlich equation described the removal of Cu(II) ions. The maximum Langmuir capacities were up to 285.71, 416.67, and 454.55 mg/g for Cu(II), Fe(II), and Mn(II), respectively. The pseudo-first-order kinetic model fitted well the metal ions removal data. The rate-controlling step reflected the involvement of surface and inner pore diffusion (intraparticle) processes. Electrostatic attractions and chelation were mainly responsible for the binding of metals ions onto SiO₂/CuFe₂O₄/PANI. The selectivity of the studied ions was governed mainly by the hydrated ionic radii and the composite adsorption active sites. SiO₂/CuFe₂O₄/PANI can be easily reused with a slight decrease (around 2–3%) in metal removal efficiency after four successive regeneration cycles.     

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.     

Equilibrium,kinetics and thermodynamics studies of Cd sorption onto a dithizone-impregnated Amberchrom CG-300m polymer resin

Amberchrom CG-300m, a styrene acrylic ester polymer resin, was studied for the first time as sorbent for metal ion sorption in a solid-phase extraction system. The polymer sorbent was modified via impregnation with dithizone to improve its efficiency. Efficiency of the modified sorbent improved by more than 47%. The loading capacity of the resin is 3.2 mg dithizone per gram of sorbent. The mechanisms of Cd(II) sorption from aqueous solutions are presented. Capacity of the modified resin for Cd(II) was investigated in batch experiments as a function of pH, initial metal ion concentration, temperature and time. Maximum capacity of 0.551 mg Cd(II) per gram of sorbent was achieved. The dimensionless separation factor, 0 < R_L < 1, associated with the Langmuir isotherm (at T = 294 K) signifies sorption of Cd(II) was favorable, as do negative values of free energy of sorption (ΔG) at temperatures exceeding 293 K. Sorption was endothermic (ΔH > 0) while ΔS > 0 reflects the affinity of the sorbent towards Cd(II). The pseudo-second order model proved to be the best fit model for Cd(II) sorption kinetics data. Particle-diffusion models suggest sorption follows film as well as pore diffusion mechanisms.     

An innovative SiO2-pyrazole nanocomposite for Zn(II) and Cr(III) ions effective adsorption and anti-sulfate-reducing bacteria from the produced oilfield water

Novel SiO₂-pyrazole (SiO₂-PYZ) nanocomposite was introduced for the elimination of Zn(II) and Cr(III) from oil reservoir water. Characterization analysis of prepared SiO₂-PYZ nanocomposite was investigated using SEM, FTIR, TGA, XRD, TEM, and BET. Studying the effects and optimization of the parameters such as retention time, pH, initial Cr(III) and Zn(II) ions concentrations, adsorbent dosage, and temperature were examined. For kinetics investigation, the pseudo-second-order (PSO) model matches the adsorption process effectively under different operating conditions. After applying two other isotherm models (Langmuir and Freundlich), the experimental data was adequately equipped with Langmuir, R² = 1. The thermodynamic results pointed that the adsorption of Zn(II) and Cr(III) ions was spontaneous, endothermic, and physisorption reaction. At pH 12, the influence of more than one ion, such as Ca(II) and Na(I), was checked, and the results revealed that this conjugate substance was highly selective to Cr(III). After washing with water in multiple cycles, the adsorbed material was regenerated with 0.1 M HCl and subsequently reused without deterioration in its case cavities. Interestingly, SiO₂-PYZ was highly effective against sulfate-reducing bacteria (SRB) in the petroleum field.