Maximum Adsorption Capacity Values Research Articles

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.

Kinetic and Equilibrium Function and Switchable Catalytic Activity of Some Thermo-Responsive Hydrogel Metal Absorbents Based on Modified PNIPAM

Synthesis and identification of some thermo-responsive hydrogel metal absorbents based on Schiff base modified PNIPAM is described. PNIPAM hydrogel is produced through conventional free-radical polymerization method. The hydrogel is amino modified with different amines and then treated with various aldehydes to make polymeric Schiff-bases supposing to utilize as an absorbent for Cu salt. Characterization of the as-prepared hydrogels was performed properly and confirmed the corresponding structures. Kinetic and equilibrium function of the absorbents and the effect of distinct variables like pH, adsorbent amount and contact time in the absorption process are investigated in detail. Kinetic and adsorption isotherm data agreed with pseudo-second order model and Langmuir isotherm, respectively. The maximum value of adsorption capacity of the prepared adsorbent was around 8550 mg g−1. In addition, the corresponding switchable catalytic activity using one of the thermo-responsive hydrogel metal absorbents in the reduction of 4-nitro phenol to 4-amino phenol in the role of model reaction is examined.

Isothermal adsorption characteristics of various phases of CO2 and CH4 in different rank coals

ABSTRACT Using the remaining coal seams of closed coal mines for CO2 geological storage can effectively slow down the greenhouse effect and realize the redevelopment and utilization of closed coal mines. The burial depth of coal seams in closed coal mines in China covers an extensive range, and CO2 and CH4 could exist in various phases in the coal. The existing experimental objects for CO2 adsorption in coal are mainly associated with the supercritical and gaseous phases, and a research gap comparison between the CO2 adsorption characteristics in the liquid phase and those of other phases is very obvious. Herein, the isotherm adsorption experiments of CO2 and CH4 in different phases on different rank coal samples are methodically conducted in the pressure range of 0-12MPa. The experimental results indicate that the excess adsorption capacity of gaseous CO2 and CH4 (gas pressure <4MPa) rapidly raises with the growth of the adsorption pressure; however, a significant difference for the case of the medium- and high-pressure stage (>4MPa) is detectable. With the growth of the adsorption pressure, the excess adsorption capacity of the supercritical CH4 gradually reaches the maximum value and then remains stable, where the maximum experimental value is 1.009 mmol/g. While the excess adsorption capacity of CO2 near the critical pressure of liquid and supercritical state rapidly reduces and then tends to be stable. The maximum adsorption capacity is capable of touching 2.096 mmol/g, which is stable around 0.5 mmol/g. The analysis indicates that the change in the excess adsorption amount of CO2 near the critical pressure corresponds to the change in its density. The absolute adsorption capacity of CO2 and CH4 monotonically grows in the pressure range of 0-12MPa, and the absolute adsorption capacity of the same coal sample follows the following order: liquid CO2 > supercritical CO2 > CH4. The maximum adsorption capacity values for these substances in order are 2.493, 2.345, and 1.296 mmol/g. With the growth of the coal rank, the Gibbs free energy, specific surface area, and adsorption capacity of the understudied coal samples exhibit a U-shape relationship as a function of their coal ranks.

Efficient removal of congo red dye using activated lychee peel biochar supported Ca-Cr layered double hydroxide

Congo red is a known carcinogenic and mutagenic dye, so its presence in bodies of water is dangerous. The present work aims to synthesize and characterize a layered double hydroxide (LDH)-biochar composite and evaluate its application in the adsorption of Congo red dye (CR). CaCr/LDH was anchored over lychee activated biochar through coprecipitation. The composite was characterized using scanning electronic mapping (SEM), energy-dispersive spectrometer SEM (EDS-SEM), Fourier transform infrared (FT-IR), X-ray powder diffractometry (XRD) and Brunauer-Emmet-Teller (BET). The effect of pH, adsorption kinetics, isotherms, ionic strength, and thermodynamic parameters were evaluated. The pH results show a stable adsorption capacity in a useful range of pH (pH 4–9). Adsorption kinetics fitted the Elovich model, suggesting a heterogeneous system. The maximum adsorption capacity value (qe) calculated was achieved by applying the Sips model, with 631.1 mg g−1 at 50 °C. Ionic strength experiments show that the capacity increased with increasing NaCl concentration, which is desirable for real use as other ions are commonly present in dye wastewater. π-π interactions and hydrogen bonding seems to be involved in the adsorption mechanisms. CaCr-LDH/lychee biochar has better structure stability over several adsorption–desorption cycles with anionic exchange regeneration (in comparison with thermal regeneration), wide operational pH and high adsorption capacity. Therefore, this new composite presents a very good potential for the adsorption of dye from waste- or ground- water.

3D graphene sponge biomass-derived with high surface area applied as adsorbent for nitrophenols

The present work used wood sawdust as a carbon precursor to produce 3D graphene sponge material, a carbon material with an added value, successfully used as an adsorbent for removing o-nitrophenol and p-nitrophenol from aqueous effluents. The resulting material’s structural, morphological, textural, and chemical characteristics (WS-Graphene) were evaluated. Textural analysis revealed a high surface area (∼3000 m2g−1) and high total pore volume (1.38 cm3 g−1). Raman, infrared and X-ray diffraction techniques evidenced the presence of a few layers of graphene, with some fraction of defects. Transmission electron microscopy confirmed the presence of a 3D-packed structure for the graphene. These WS-Graphene characteristics favored its application as an adsorbent for removing o-nitrophenol and p-nitrophenol pollutants. The adsorption process of both nitrophenols was extremely rapid and reached the equilibrium time in less than 5 min when the concentration of both adsorbates was fixed at 700 mg L−1. Furthermore, the maximum adsorption capacity (Qmax) values were 1842 mg g−1 (o-nitrophenol) and 879.6 mg g−1 (p-nitrophenol) at 30 °C. These results confirm that the WS-Graphene adsorbent acts as a 3D sponge. Langmuir’s isothermal was the best-fitted model for both nitrophenols in aqueous solution. The o-nitrophenol adsorption onto WS-Graphene might follow pseudo-second-order as well as general-order, while the adsorption of p-nitrophenol might follow only the general-order model. Thermodynamic studies revealed a spontaneous and endothermic adsorption process. The WS-Graphene adsorbent presents a high percentage (∼97 %) of removing the mixture of pollutants in effluents, showing an excellent adsorption capacity and making it a potential material to remove industrial wastewater.

Highly adsorptive removal of palladium and platinum ions from wastewater using novel ethylenediamine-glutaraldehyde-grafted metal organic framework

Herein, a metal–organic framework (MIL-101(Cr)) was synthesized and functionalized with ethylenediamine-glutaraldehyde (ED-GA for removal of palladium (Pd2+) and platinum (Pt4+) from wastewater. The chemical structure, surface properties, morphology, and adsorption energy of the prepared materials, MIL-101(Cr) and MIL-101(Cr)/ED-GA were analyzed using several analytical techniques and density functional theory (DFT). The prepared MIL-101(Cr)/ED-GA was efficient in removing Pd2+ and Pt4+ from aqueous solution with the percentage removal reaching 95% for Pd2+ and 85% for Pt4+. Furthermore, the adsorption data demonstrated a good fit to the Langmuir isotherm model and gave the maximum adsorption capacity values of 416.17 mg g−1 for Pt4+ and and 322.6 mg g−1 for Pd2+ ions. Kinetics data obeyed a pseudo-second-order model and revealed the rapid adsorption of Pd2+ and Pt4+ ions by MIL-101(Cr)/ED-GA which reached equilibrium within 10 and 40 min, respectively. Lastly, DFT studies revealed that the adsorption of Pd2+ ions by the composite forms a more thermodynamically stable compound than adsorption of Pt4+, suggesting that the material easily interacts with Pd and high selectivity is thus expected. This was indeed confirmed by experimental selectivity test results. Owing to their high affinity for PGMs, N atoms depicted large adsorption energy values compared to other adsorption sites. The MIL-101(Cr)/ED-GA could act as an efficient and cost effective adsorbent for removal of platinum group metals from wastewater.