Maximum Adsorption Capacity Values Research Articles

Hybrid nano-biocomposite based on polysaccharide and graphene oxide for the practical separation of proteins in a fixed bed adsorption column

Proteins and amino acids are essential to humans and all living beings. Moreover, these compounds are present in the pharmaceutical, food, and cosmetic industries. Proteins need to be purified for use in industry. This work aims to synthesize and apply a nano-biocomposite based on graphene oxide (GO) and agar (polysaccharide) for protein separation and purification. The hydrogel composite was tested for myoglobin (Mb) adsorption, the effect of changing the initial pH in Mb adsorption, and the ionic strength was evaluated. The adsorptive capacity values were higher at pH=5 and 6 and decreased at higher pH values. The increase in NaCl concentration did not affect the adsorptive capacity significantly. The composite exhibited a notorious value of maximum experimental adsorption capacity in the equilibrium of over 790 mg g−1 at pH=5 and 25 °C. As GO interacts with the polymeric agar matrix, resulting in a 3D material, the material developed could adsorb Mb in a fixed bed column and single and binary (BSA+Mb) systems. There are indications that the GO-based composite possibly forms a complex with the peptide ligands of myoglobin, forming a protein corona, making Mb desorption difficult.

Synthesis of Porous Red Mud/Slag-Based Spherical Geopolymers for Efficient Methylene Blue and Ni2+ Removal from Water.

To reuse red mud and slag wastes as raw materials, a green type of porous spherical red mud/slag-based geopolymer (RSG) was synthesized by utilizing suspension curing and foaming techniques. Because methylene blue (MB) and nickel ion (Ni2+) were common and difficult to treat in wastewater, the adsorption characteristics of MB and Ni2+, as well as the phase and microstructure of the porous RSG spheres prior to and after adsorption, were thoroughly investigated. The porous RSG spheres showed a stable and mesoporous structure with a BET surface area of 31.36 m2/g. The spheres achieved the maximum removal efficiencies of 99.81% (MB) and 99.01% (Ni2+) at dosages of 16 and 10 g/L, respectively. The pseudo-second-order kinetic model and the Langmuir model could match the adsorption data of these spheres, with predicted maximum adsorption capacity (Qmax) values of 19.88 mg/g for MB and 12.39 mg/g for Ni2+, respectively. After three adsorption-desorption cycles, porous RSG spheres demonstrated good recycling capability with removal efficiencies of 98.10% (MB) and 54.60% (Ni2+). The spheres were also effective in adsorbing additional dyes (methyl orange (MO), crystal violet (CV), and malachite green (MG)) and heavy metal ions (Cd2+, Pb2+, Zn2+, and Cu2+). The spheres have potential use in water treatment.

A novel potato peels waste β-cyclodextrin biocomposite for the efficient uptake of diuron and glyphosate herbicides.

A novel biocomposite (FPPW-β-CD) was prepared by a simple and sustainable method involving fine potato peel waste, β-cyclodextrin (β-CD), and green citric acid through the crosslinking reaction. The polymer was characterized using SEM, FTIR, XRD, TGA, and DSC analyses. The adsorbent performance was evaluated about the glyphosate and diuron adsorption from the aqueous solution. Pesticide removal was investigated regarding the influence of solution pH, temperature, and initial concentration of contaminants. Also, it highlights the main interactions involved in the adsorption phenomenon based on the pH effect and characteristics of adsorbent and adsorbate molecules. The maximum adsorption capacity values according to the Sips model were higher than 2000µgg-1. The pseudo-second-order and general-order models described the kinetic data well. Thermodynamic parameters indicated that pesticide removal was spontaneous and favorable. The magnitude of enthalpy variation values (27.37kJmol-1 and - 100.79kJmol-1) revealed that the glyphosate and diuron adsorption occurred through the physisorption and chemisorption, respectively. The novel biocomposite is a promising green adsorbent for the uptake of micropollutant pesticides in aqueous solutions at concentrations of µg L-1.

Methylene blue dye elimination from synthetic wastewater by modified adsorbent produced from Foeniculum vulgare waste: Thermodynamic, equilibrium, and kinetic studies

In the current investigation, seeds of the Foeniculum vulgare plant were acquired from the KSA, Tabuk City, and its powder was chemically modified by four different reagents. The four resulting samples were identified by SEM and IR techniques and inspected for methylene blue (MB) dye adsorption. The influence of MB concentration, adsorbent dose, solution pH, temperature, and contact time on adsorption performance was examined. This adsorption's kinetic, isothermal, and thermodynamic parameters were correspondingly studied. The idyllic adsorbent was established to be the modified sample with oxalic acid, which removed 90.15 % of the MB dye. It was also shown that the MB adsorption matched well with the kinetically 2nd -order model. The findings of the experiment fit better with the model of Langmuir isotherm than the other models. The negative values of each ΔG°, ΔH°, and ΔS° indicate the adsorption of MB is an exothermic and spontaneous process. The very law value of adsorption enthalpy proves the physisorption adsorption. The very high maximum adsorption capacity (qmax) values of this adsorption (892.857, 684.932, 487.805 mg g−1), the stability and availability and of this oxalic acid modified adsorbent suggest it will be highly valued in the field of water decontamination.

Characteristics of Phosphate Sorption on Surface Sediments: A Study in Kendari Bay

Phosphate adsorption and desorption are significant processes that influence the presence of phosphate in aquatic ecosystems and regulate the concentration of phosphate at the water-sediment interface. This research aims to investigate the characteristics of phosphate adsorption and desorption in Kendari Bay sediments, study the relationship between adsorption capacity and sediment characteristics and its phosphorus fraction, and evaluate its potential contribution to the overlying water column. Physicochemical measurements of the water and sediments were performed in the sampling location and the laboratory. Two types of adsorption-desorption kinetics models and two types of isothermal adsorption models were used to estimate the adsorption rate and capacity of the surface sediments. Adsorption kinetics and desorption kinetics experiments produced pseudo-second-order kinetic model equations with regression coefficients (R2) of 0.865–0.936 and 0.886–0.947, respectively. The isothermal adsorption experiment follows the Langmuir equation model with R2 = 0.964. The maximum adsorption capacity (Qmax) value was 156.3–227.3 mg/kg, and the phosphate concentration value at zero equilibrium (EPC0) was 0.0026–0.0047 mgP/L. Notably, the EPC0 value was higher than the SRP concentration, indicating that the resuspension of phosphate ions from sediment into the water column could occur. Furthermore, there was a correlation between Qmax values with OP, Al-P, Fe-P, clay particles, and organic materials. Potential practical applications may include integrating sediment adsorption capacity data into ecosystem models to inform nutrient management strategies and promote sustainable coastal development in Kendari Bay and beyond.

Understanding adsorption mechanisms and metal ion selectivity of superparamagnetic beads with mesoporous CMK-3 carbon and commercial activated carbon

This study investigates, the adsorption capacities of synthesized magnetic hybrid beads containing ordered mesoporous carbon (CMK-3) and commercial activated carbon (commercial AC) for Cd (II), Ni (II), and Hg (II) ions adsorption in single and ternary systems. The order of maximum adsorption capacity was Cd (II) > Ni (II) > Hg (II) in both beads and systems. L13 beads containing CMK-3 exhibit superior adsorption efficiency compared to L3 beads with commercial AC, attributed to the large surface area, enhanced accessibility to adsorption sites, and the presence of O=C bonds, as well as other elements such as F−. Adsorption of all metal ions was described by Freundlich isotherm in L3 beads in both systems, meanwhile in L13 beads, Langmuir and Freundlich models described adsorption differently in both systems and among metal ions, indicating a more complex process. According to the reported maximum adsorption capacity values, L3 beads exhibit a greater affinity for Hg (II) ions, while L13 beads show a higher affinity for Cd (II) and Ni (II) ions. Adsorption in both beads occurred through several mechanisms involving surface complexation, ion-exchange, precipitation, physical and chemical processes. These findings highlight the importance of material design in optimizing adsorption performance for environmental applications, with potential for further enhancement of adsorption capacities and selectivities through future research.

Removal of Heavy Metal Ions (Pb2+, Co2+, and Cd2+) by Activated Carbon from Cypress Fruit: An Investigation of Kinetics, Thermodynamics, and Isotherms

In this study, activated carbon cloth (ACC) derived from cypress fruit was employed to investigate the adsorption of Pb2+, Cd2+, and Co2+ from synthetic aqueous systems. The correlation between adsorption features (pH, adsorbent dosage, temperature, initial ion concentration, and contact time) and adsorbent removal efficiency was investigated. Analysis by FT-IR, SEM, and EDS was employed to confirm the adsorption of metal ions onto the ACC. Results revealed the best adsorption efficiencies for heavy metal ions were attained at pH = 7, 11, 6; the adsorbent dosage of 0.06, 0.08, and 0.04 g for Pb2+, Cd2+, and Co2+, respectively; the ion initial concentration of 50 mg·L−1 for Pb2+ and 70 mg·L−1 for both Co2+ and Cd2+; and contact time of 90 minutes for both Pb2+ and Co2+ and 120 minutes for Cd2+. Kinetic studies exposed the second-order adsorption of all aforementioned heavy metal ions. Additionally, the equilibrium data were fitted by Langmuir and Freundlich’s isotherms, while the former performed better than the latter. The maximum adsorption capacity values for Pb2+, Co2+, and Cd2+ were attained to 81.87, 55.30, and 117.3 mg·g−1, respectively. Considering the thermodynamic data, the studied processes were exothermic and spontaneous.

A novel nanocomposite-based zeolite for efficient remediation of Cd-contaminated industrial wastewater

Novel nanocomposite sorbent was produced by depositing nanostructured water treatment residual (nWTR) onto zeolite (Ze) using high-energy ball milling process. The physicochemical properties of nanocomposite (Ze-nWTR) prior and after Cd adsorption were analyzed by SEM–EDX, FTIR, BET and XRD. A batch study of cadmium adsorption (Ze-nWTR) was performed at various process parameters (sorbent dose, contact time, solution pH, competing ions, initial concentration and temperature). The obtained data were fitted to various equilibrium and kinetics models. The Langmuir and power function models successfully described Cd adsorption equilibrium and kinetic processes, respectively. The maximum adsorption capacity (qmax) value of Cd by Ze-nWTR nanocomposite (147 mgg−1) was 3 and 5.9 times higher than those of nWTR and zeolite sorbents, respectively. Increasing temperature from 287 to 307 K has resulted in increasing the maximum Cd adsorption capacity (qmax) of the nanocomposite from 147.9 to 270 mgg−1. The calculated thermodynamics parameters suggested physical and chemical attraction between Cd and Ze-nWTR and the association of dissociative mechanism in Cd(II) sorption process. The excellent reusability and Cd removal ability of Ze-nWTR nanocomposite (98%) from industrial wastewater confirm its potential as promising adsorbent for wastewater treatment applications.

Synthesis of sustainable mesoporous sulfur-doped biobased carbon with superior performance sodium diclofenac removal: Kinetic, equilibrium, thermodynamic and mechanism

Over the last years, the strategy of employing inevitable organic waste and residue streams to produce valuable and greener materials for a wide range of applications has been proven an efficient and suitable approach. In this research, sulfur-doped porous biochar was produced through a single-step pyrolysis of birch waste tree in the presence of zinc chloride as chemical activator. The sulfur doping process led to a remarkable impact on the biochar structure. Moreover, it was shown that sulfur doping also had an important impact on sodium diclofenac (S-DCF) removal from aqueous solutions due to the introduction of S-functionalities on biochar surface. The adsorption experiments suggested that General and Liu models offered the best fit for the kinetic and equilibrium studies, respectively. The results showed that the kinetic was faster for the S-doped biochar while the maximum adsorption capacity values at 318 K were 564 mg g−1 (non-doped) and 693 mg g−1 (S-doped); highlighting the better affinity of S-doped biochar for the S-DCF molecule compared to non-doped biochar. The thermodynamic parameters (ΔH0, ΔS0, ΔG0) suggested that the S-DCF removal on both adsorbents was spontaneous, favourable, and endothermic.

Synthesis and characterization of surface-modified magnetic mesoporous silicate materials for phosphate adsorption.

The magnetic mesoporous silica material, Mag-MCM-41, was synthesized by coating magnetite (Fe3O4) nanoparticles with a mesoporous material called MCM-41. Mag-MCM-41 and modified nanomaterials Mag-MCM-41-NN and Mag-MCM-41-NN-Fe+3 which were modified with aminopropyl functional groups. In water and wastewater, phosphate anions are considered significant contaminants due to their detrimental impact on the environment. They promote the growth of algae, leading to eutrophication. The purpose of this study is to investigate the removal of phosphate anions from aqueous solutions using modified magnetic silica particles. The Mag-MCM-41 material exhibits hexagonal properties and belongs to the class of "mesoporous" materials. It has a surface area of 923 m2.g-1, which was determined through N2 adsorption-desorption isotherms, FTIR, TEM, BET, and SAXS analysis. Kinetic and adsorption isotherm studies were conducted using Mag-MCM-41, Mag-MCM-41-NN, and Mag-MCM-41-NN-Fe+3 adsorbents to examine the behavior of phosphate anions. The kinetic and adsorption isotherm studies of phosphate anions revealed that the adsorption process on Mag-MCM-41, Mag-MCM-41-NN, and Mag-MCM-41-NN-Fe+3 adsorbents followed the chemical adsorption mechanism. Phosphate adsorption on all adsorbents occurred in a monolayer, and the MCM-41-NN-Fe+3 adsorbent exhibited the highest maximum adsorption capacity (qm) value of 112.87 mg.g-1 compared to the other adsorbents.

Facile preparation of sulfonated carbon particles with pomegranate peels as adsorbent for enhanced methylene blue adsorption from aqueous solutions

AbstractIn this study, in the first stage, activated carbon (AC) is produced from pomegranate peels, which are commonly found in Turkey, by pyrolysis after impregnation with NaOH (PPAC). In the second stage, the surface properties of the obtained PPAC sample are further improved by the sulfonation modification process with sulphuric acid (PPAC-S) for selective MB adsorption. For the characterization of the obtained samples, XRD, FTIR, SEM, nitrogen adsorption/desorption and EDS analyses were performed. Additionally, the zero charge points (pHzpc) of these samples were also determined. The isotherm, kinetic, and thermodynamic properties of the MB adsorption process with PPAC-S were examined. The qe values obtained for MB adsorption with PPAC and PPAC-S samples were found to be 98.79 mg/g and 199.18 mg/g, respectively. There is an increase of 100% in MB adsorption with the sulfonated PPAC adsorbent. Maximum adsorption capacity values of MB with the Langmuir model at temperatures of 298, 308, and 318 °C were 212.7, 216.9, and 245.1 mg/g, respectively. Additionally, the mechanism of MB adsorption onto PPAC-S was also attempted to be elucidated.

Design and performance assessment of novel Fe3O4 decorated nanoblend of guar gum/graphene oxide flakes and CuO for mitigation of fluoroquinolones from wastewater

Organic-inorganic nanoblends particularly, polysaccharide-blended-inorganic ones, possess interesting properties and hence versatile applications, due to which they have become the focus of much research attention, lately. The present study reports the fabrication of magnetic guar gum/graphene oxide nanocomposite blended with CuO to obtain a novel nanoblend, mGG/GO/CuO NB, through a two-stepped synthesis route: preparation of GO via Improved Hummers technique followed by mGG/GO/CuO NB preparation using co-precipitation method. The nanocomposite was subsequently investigated for its capacity for adsorptive elimination of ciprofloxacin from aqueous medium. It was identified using typical physico-chemical techniques, such as XRD, Raman, and FTIR spectroscopy; EDX and FESEM for morphological investigation; as well as VSM, pHZPC and TGA. The Langmuir isotherm model and the pseudo second order model are obtained as the isotherm model and kinetic model that can best depict the adsorption behaviour. The Langmuir isotherm model provided an outstanding maximum adsorption capacity value of 769.23 mg g−1 for CPX removal. Thermodynamics studies witness a spontaneous adsorption with an exergonic behaviour supported by a ΔGo value of −11.74 kJ mol−1 and ΔHo value of −49.976 kJ mol−1 as well as an increase in ΔSo value (+189.32 mol−1). Columbic/electrostatic interactions, hydrophobic interactions, hydrogen bonds, and electron-donor-acceptor (EDA) interactions are the main interacting forces predicted to be pivotal in the adsorption mechanism.

Use of the Box–Behnken Experimental Design for the Optimization of Orange II (Acid Orange 7) Adsorption on Aloe vera

Industrial wastewater effluents containing dyes are considered to pollute and be harmful to the environment. Among the various removal techniques, the adsorption process using low-cost adsorbents has been successfully used to remove pollutants. In this work, Aloe vera leaves (AVs) have been used as adsorbent for the removal of Orange II (O-II). A three-level three-factor Box–Behnken factorial design, including three replicates of center points, was applied to investigate the main parameters affecting the biosorption of O-II dye in aqueous solutions by AVs. The selected parameters were adsorbent dose, initial dye concentration, and contact time. The Box–Behnken experiment design has given a satisfactory result for the optimization of the adsorption process. The obtained value of R2 (0.9993) shows that the quadratic response model adequately represents the relationship between each response and the chosen variables. The pH influences the adsorption capacity, obtaining at pH 2 the maximum adsorption capacity value. From the kinetic models studied, the one that best describes the adsorption of Orange II on Aloe vera is the Bangham model (ARE = 1.06%). The isotherm model that best represents the experimental data is the Toth model. The maximum adsorption capacity obtained by this model was 15.9 mg·g−1.

Microwave‐Assisted Soft Method for Synthesis of Poly (Acrylic Acid)/Organo‐clay Composites: Application As Superabsorbent For Phenol and Cr (VI)

AbstractA series of superabsorbent composites (PAA/HDTMA‐MMT) based on poly (acrylic acid) (PAA) and different content of organo‐modified natural clay HDTMA‐MMT (1,3 and 5 wt.%) were synthesized via in‐situ radical polymerization using microwave method. This eco‐friendly route was chosen to avoid the use of toxic solvents and reduce polymerization time. In addition, it can be considered an efficient approach for industrial‐scale polymer synthesis. The microstructure of the obtained hydrogels was evidenced by Fourier transformation infrared spectroscopy (FTIR), X‐ray diffraction (XRD), and scanning electron microscopy (SEM). Thermal stability was examined according to nano‐filler content on the matrix. The composite (PAA/HDTMA‐MMT) at 3 wt % exhibits an important swelling capacity value (833.33 g g−1). The efficiency of the synthesized hydrogel composites for phenol and Cr (VI) uptakes from aqueous solutions was studied in batch experiments. The main reason for their selection is their remarkable industrial use, despite their high toxicity and persistence in the environment. In order to underline the mechanism of the phenol and Cr (VI) adsorptions on the (PAA/HDTMA‐MMT), respectively, the zeta potential of the hydrogel was evaluated. Maximum adsorption capacity values of 170.7 mg g−1 and 197.3 mg g−1 were screened for phenol and Cr(VI), respectively. The adsorption process concurs with pseudo‐second‐order kinetics and with the Langmuir isotherm equation. A very high adsorption capacity (qmax=225.2 mg g−1) and a correlation coefficient of 0.998 calculated from isotherm equations show the high efficiency of the adsorbent and thus expected to be a good adsorbent candidate for wastewater treatment. The thermodynamic studies evidenced the exothermic character of the adsorption reactions of the studied pollutants.

Adsorptive removal of ciprofloxacin from aqueous medium by magnetic guar gum grafted graphene oxide nano composite

In view of the huge quantum of harmful pharmaceuticals being released into the water stream from various sources, eradication or reduction of these harmful chemicals to a minimum permissible limit is of primary importance. The current work reports a two-step fabrication of magnetic guar gum graphene oxide nanocomposite, mGG/GO NC, a bio nanocomposite based on guar gum polymer blended with Graphene oxide decorated with magnetic nanoparticles. It was subsequently examined for its adsorption ability for the sequestration of ciprofloxacin form wastewater. Various techniques including XRD, Raman and FTIR spectroscopy, HRTEM, EDX, FESEM, VSM, pHZPC, and TGA have been employed for the characterization of guar gum as well the nanocomposite. Experimental kinetic and isotherm data obtained from batch adsorption studies when fitted into known models reveals that pseudo second order model and Langmuir isotherm model can best illustrate the behavior of the adsorption process. Thermodynamic studies carried out at varying temperatures confirm the spontaneity and exothermic nature of the adsorption phenomenon. Moreover, a significant extent of recyclability of the nanocomposite is predicted with a retention of adsorption efficiency up to several cycles of adsorption-desorption studies. The novel natural polysaccharide-based nanocomposite can prove to be an excellent adsorbent as evident from a considerably high maximum adsorption capacity value of 555.56 mg g−1. Numerous interactions such as hydrogen bonding, electrostatic, electron-donor acceptor (EDA) or π − π interactions, and hydrophobic interactions act as driving forces in the adsorption mechanism; a synergistic effect of all these interactions may have plausibly resulted in such an excellent adsorption capacity exhibited by mGG/GO NC.

Surface modification of natural clay with H2O2 for high adsorption of acid Red 114: Experimental and modelling studies

The water contamination problem caused by dyes and the understanding of their adsorption mechanism in aqueous media is still significant nowadays. This study investigates the adsorption performance of natural montmorillonite clay treated with H2O2 (MMT-H2O2) and employed as an adsorbent to remove Acid Red 114 (AR-114) from aqueous solutions. MMT-H2O2 and the natural clay without treatment (MMT) were analysed using different analytical techniques such as XRF, XRD, FESEM, EDS, FTIR, TGA/DTG, N2-adsorption/desorption curves, CHNS/O analysis, hydrophobicity Index (HI). It also provides a theoretical analysis of the adsorption phenomenon utilising Statistical Physics methods to understand the adsorption mechanism between AR-114 and MMT-H2O2 adsorbent associated with batch adsorption conditions and adsorption equilibrium. The treated clay with H2O2 showed a higher oxygen content and a better adsorption capacity than the untreated one. The maximum adsorption capacity (Qmax) values obtained with the best-fitted model (Liu) ranged from 421.9 and 1178.5 mg g−1. This high adsorption capacity for AR-114 dye can be explained by considering the remarkable characteristics of the MMTH2O2 material, such as high oxygen content, variety of surface functional groups, porous interlayer structure, and hydrophilicity. The computational adsorption results suggest that the AR-114 molecules adsorbed onto the surface site of the MMTH2O2 adsorbent in a perpendicular orientation. This indicates that the n2 values increased as the operating temperature was raised, demonstrating the endothermic accumulation of dye molecules on the treated clay mineral surface. Moreover, the temperature-dependent adsorption energies (E1 and E2) levels were less than 40 kJ mol−1, highlighting the primary physical interactions between AR-114 and MMTH2O2 clay mineral by electrostatic attraction and hydrogen bonding.

Fabrication of Nitrogen-Doped Carbon@Magnesium Silicate Composite by One-Step Hydrothermal Method and Its High-Efficiency Adsorption of As(V) and Tetracycline.

Tetracycline (TC) and arsenic contaminants are two main pollutants in aquaculture and livestock husbandry, and they have drawn worldwide attention. To address this issue, a novel N-doped carbon@magnesium silicate (CMS) was fabricated via a facile and low-cost hydrothermal route, adopting glucose and ammonia as C and N sources, respectively. The synergetic combination of carbon and magnesium silicate makes CMS possess a high surface area of 201 m2/g and abundant functional groups. Due to the abundant C- and N-containing functional groups and Mg-containing adsorptive sites, the maximum adsorption capacity values of CMS towards As(V) and TC are 498.75 mg/g and 1228.5 mg/g, respectively. The type of adsorption of As(V) and TC onto CMS is monolayer adsorption. An adsorption kinetic study revealed that the mass transfer and intraparticle process dominates the sorption rate of As(V) and TC adsorption onto CMS, respectively. Various functional groups synthetically participate in the adsorption process through complexion, π-π EDA interactions, and hydrogen bonds. This work provides a one-step, low-cost route to fabricate a N-doped carbonaceous adsorbent with a high surface area and abundant functional groups, which has great potential in the application of practical sewage treatment.

Synthesis of novel mesoporous selenium-doped biochar with high-performance sodium diclofenac and reactive orange 16 dye removals

In this study, for the first time, a selenium-doped mesoporous biochar was prepared and efficiently employed for sodium diclofenac and reactive orange 16 dye adsorption. The characterization results indicated that selenium doping had a remarkable impact on Biochar-Se morphological and physicochemical structures. The efficacy of developed biochar samples on reactive orange 16 (RO-16) and diclofenac (DCF) removals was fully investigated. For both molecules (DCF and RO-16), Liu's equilibrium model offered the best fitness with maximum adsorption capacity values of 355 mg g−1 for DCF and 538 mg g−1 for RO-16 for Biochar-Se. Multiple mechanisms including pore filling, π-π interaction, and hydrogen bonding between the Biochar-Se and DCF/RO-16 molecules were involved in the adsorption process. Se-nanoparticles formed metal–oxygen bonds, which boosted the adsorption of DCF and RO-16 molecules. The current work offered a feasible approach for the development of Se-doped biochar adsorbent that is incredibly effective in treating wastewater.

Activated carbon prepared from Brazil nut shells towards phenol removal from aqueous solutions.

The Brazil nut shell was used as a precursor material for preparing activated carbon by chemical activation with potassium hydroxide. The obtained material (BNSAC) was characterized, and the adsorptive features of phenol were investigated. The characterization showed that the activated carbon presented several rounded cavities along the surface, with a specific surface area of 332 m2g-1. Concerning phenol adsorption, it was favored using an adsorbent dosage of 0.75g L-1 and pH 6. The kinetic investigation revealed that the system approached the equilibrium in around 180min, and the Elovich model represented the kinetic curves. The Sips model well represented the equilibrium isotherms. In addition, the increase in temperature from 25 to 55°C favored the phenol adsorption, increasing the maximum adsorption capacity value (qs) from 83 to 99mgg-1. According to the estimated thermodynamic parameters, the adsorption was spontaneous, favorable, endothermic, and governed by physical interactions. Therefore, the Brazil nut shell proved a good precursor material for preparing efficient activated carbon for phenol removal.

Synthesis and Characterization of Novel Magnetic Nano-Biocomposite Hydrogels Based on Starch-g-poly(acrylic acid) Reinforced by Cellulose Nanofibers for Cu2+ Ion Removal.

One of the crucial challenges of the adsorption process is to recapture the adsorbent from the solution, especially for adsorbents in powder form. This study synthesized a novel magnetic nano-biocomposite hydrogel adsorbent to successfully remove Cu2+ ions, followed by convenient recovery and reusability of the adsorbent. The Cu2+ adsorption capacity of starch-g-poly(acrylic acid)/cellulose nanofibers (St-g-PAA/CNFs) composite hydrogel and magnetic composite hydrogel (M-St-g-PAA/CNFs) was investigated and compared in both bulk and powder forms. Results showed that Cu2+ removal kinetics and swelling rate were improved by grinding the bulk hydrogel into powder form. The kinetic data and adsorption isotherm were best correlated with the pseudo-second-order and Langmuir models, respectively. The maximum monolayer adsorption capacity values of M-St-g-PAA/CNFs hydrogels loaded with 2 and 8 wt % Fe3O4 nanoparticles in 600 mg/L Cu2+ solution were found to be 333.33 and 555.56 mg/g, respectively, compared to 322.58 mg/g for the St-g-PAA/CNFs hydrogel. Vibrating sample magnetometry (VSM) results demonstrate that the magnetic hydrogel that included 2 and 8 wt % magnetic nanoparticles exhibited paramagnetic behavior with the magnetization of 0.6-0.66 and 1-1.04 emu/g at the plateau, respectively, which showed a proper magnetic property and good magnetic attraction in the magnetic field for separating the adsorbent from the solution. Also, the synthesized compounds were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and Fourier transform infrared spectroscopy (FTIR). Finally, the magnetic bioadsorbent was successfully regenerated and reused for four treatment cycles.