Synthesis,structural characterization and Cu(ii) adsorption behavior of manganite (γ-MnOOH) nanorods

New alternatives for the removal of transition metal ions that present an environmental risk are required. The chemical adsorption of these ions on surfaces with chemisorbent properties represents a promising area of research. In this work, manganite (γ-MnOOH) nanorods were synthesized, with a surface area of 20.22 m² g⁻¹, pore size of 32.18 nm and pore volume of 0.1627 cm³ g⁻¹. After chemical and structural characterization of the manganite sample, it was evaluated as an adsorbent of Cu(ii) from aqueous solution. The equilibrium adsorption data were well fitted by the Langmuir isotherm, and the results indicated that the maximum adsorption capacity of Cu(ii) was 11.926 mg g⁻¹. Cu(ii) ion adsorption on the manganite surface is a spontaneous and exothermic process (ΔG°< 0 and ΔH°< 0). The negative value of ΔS° suggests the stability of the adsorption process without structural change at the manganite–aqueous solution interface. A scheme for chemisorption of Cu(ii) ions on the hydroxylated surface of manganite is proposed.

Manganite (γ-MnOOH) nanorods were synthesized and Cu(ii) adsorption on their hydroxylated surface was a spontaneous process (ΔG° < 0).     

Comparative study of Hg(ii) biosorption performance of xanthated and charred sugarcane bagasse from aqueous solutions

The main target of this study was to evaluate the efficiency of charred xanthated sugarcane bagasse (CXSB) and charred sugarcane bagasse (CSB) in the removal of Hg(ii) ions from aqueous media. Batch experiments were performed to study the experimental parameters such as effects of pH, concentration, contact time and temperature. The adsorption velocity of Hg(ii) onto CSB and CXSB was fast and reached equilibrium within 60 minutes. Isotherm and kinetic studies showed that Hg(ii) uptake using both the biosorbents followed Langmuir isotherm and pseudo second order kinetics. The maximum adsorption capacity of Hg(ii) at optimum pH 4.5 onto CSB and CXSB was found to be 125 mg g⁻¹ and 333.34 mg g⁻¹, respectively. A negative value of ΔG° and positive ΔS° value (0.24 kJ mol⁻¹ for CSB and 0.18 kJ mol⁻¹ for CXSB) for both the biosorbents confirm the spontaneous nature of Hg(ii) adsorption. A positive value of ΔH° (52.06 kJ mol⁻¹ for CSB and 30.82 kJ mol⁻¹ for CXSB) suggests the endothermic nature of biosorption. The investigated results shows that CXSB compared to CSB can be used as a low cost and environmentally benign bio-adsorbent for the removal of Hg(ii) ions from aqueous solutions.

Ion exchange adsorption mechanism of Hg(ii) onto the monomeric unit of charred xanthated sugarcane bagasse (CXSB).     

Ion-imprinted guanidine-functionalized zeolite molecular sieves enhance the adsorption selectivity and antibacterial properties for uranium extraction

The important properties in the development of adsorbents for uranium extraction from seawater include specific selectivity to uranium ions and anti-biofouling ability in the ocean environment. In this paper, we report a novel strategy for efficient selective extraction of uranium from aqueous solutions and good anti-bacterial properties by surface ion-imprinted zeolite molecular sieves. Guanidine-modified zeolite molecular sieves 13X (ZMS-G) were synthesized and used as the support for the preparation of uranium(vi) ion-imprinted adsorbents (IIZMS-G) by ligands with phosphonic groups. The prepared IIZMS-G adsorbent was characterized via Fourier transform infrared spectroscopy (FT-IR), scanning electronic microscopy (SEM), X-ray diffraction (XRD), and energy dispersive spectroscopy (EDS). The results showed that guanidine groups have been successfully introduced onto the support while its morphology structure was maintained. The adsorption performance and selectivity to U(vi) ions, antibacterial property, and reusability of IIZMS-G were evaluated. The results showed that the maximum adsorption capacity reached 141.09 mg g⁻¹ when the initial concentration of metal ions was 50 mg L⁻¹ at pH 6 and 20 °C. The adsorption process followed the pseudo-second-order kinetic model and Langmuir adsorption isotherm model. The IIZMS-G exhibits an efficient selective adsorption of U(vi) ions from aqueous solutions with competing ions. In addition, the IIZMS-G exhibited excellent inhibitory effects on Escherichia coli and Staphylococcus aureus, and the inhibitory rate was 99.99% and 98.96% respectively. These results suggest that the prepared IIZMS-G adsorbent may promote the development strategy of novel high selectivity and antifouling adsorbents for uranium recovery from seawater.

The important properties in the development of adsorbents for uranium extraction from seawater include specific selectivity to uranium ions and anti-biofouling ability in the ocean environment.     

Facile synthesis of graphene oxide from graphite rods of recycled batteries by solution plasma exfoliation for removing Pb from water

We herein present a simple, fast, efficient and environmentally friendly technique to prepare graphene oxide (GO) from graphite rods of recycled batteries by using solution plasma exfoliated techniques at atmospheric pressure. The prepared GO with an average 3 nm-thickness and 1.5 μm-length, having large surface area and high porosity, has been used to remove Pb(ii) ions from the water. The obtained results indicated that the adsorption of Pb(ii) onto GO depends on pH, contact time, temperature and initial concentration of Pb(ii). The maximum adsorption capacity of Pb(ii) onto GO determined from the Langmuir model (with a high R² value of 0.9913) was 180.1 mg g⁻¹ at room temperature. A removal efficiency of ∼96.6% was obtained after 40 min. Calculations of thermodynamic parameters (ΔG°, ΔH° và ΔS°) show the adsorption of Pb(ii) ions on the GO surface is spontaneous and intrinsically heat-absorbing. The potential mechanism can be suggested here to be the interaction of the π–π* bonding electrons and Pb(ii) as well as the electrostatic attraction between Pb(ii) and the oxygen-containing functional groups on GO.

Facile synthesis of graphene oxide from graphite rods of recycled batteries by solution plasma exfoliation for removing Pb from water.     

A pH-sensitive and sustained-release oral drug delivery system: the synthesis,characterization, adsorption and release of the xanthan gum-graft-poly(acrylic acid)/GO–DCFP composite hydrogel

In this study, graphene oxide (GO) was successfully prepared using the improved Hummers method, and the prepared GO powder was dissolved in distilled water and subjected to ultrasonic stripping. Diclofenac potassium (DCFP) was selected as a model drug to systematically evaluate the adsorption mechanism of DCFP by GO. Different reaction models were constructed to fit the adsorption kinetics and adsorption isotherms of DCFP on GO, in order to further explore the underlying adsorption mechanism. The results demonstrated that the pseudo-second-order kinetic model and Freundlich model could better delineate the adsorption process of DCFP by GO. Both π–π stacking and hydrophobic interaction were mainly involved in the adsorption process, and there were electrostatic interaction and hydrogen bonding at the same time. Then, the xanthan gum-graft-poly(acrylic acid)/GO (XG-g-PAA/GO) composite hydrogel was synthesized by in situ polymerization as a slow-release drug carrier. For this reason, a XG-g-PAA/GO–DCFP composite hydrogel was synthesized, and its in vitro drug release and pharmacokinetic data were assessed. The results showed that the synthesized XG-g-PAA/GO composite hydrogel had a certain mechanical strength and uniform color, indicating that GO is evenly distributed in this composite hydrogel. Moreover, the results of a swelling ratio test demonstrated that the swelling ratios of the XG-g-PAA/GO composite hydrogel were significantly increased with increasing pH values, implying that this material is sensitive to pH. The in vitro drug release experiment showed that the cumulative release of DCFP after 96 h was significantly higher in artificial intestinal fluid than in artificial gastric fluid. These findings indicate that the XG-g-PAA/GO–DCFP composite hydrogel exhibits pH sensitivity under physiological conditions. Besides, the results of in vivo pharmacokinetic analysis revealed that the t_1/2 of DCFP group was 2.03 ± 0.35 h, while that of the XG-g-PAA/GO–DCFP composite hydrogel group was 10.71 ± 2.04 h, indicating that the synthesized hydrogel could effectively prolong the drug action time. Furthermore, the AUC_(0–t) of the DCFP group was 53.99 ± 3.18 mg L⁻¹ h⁻¹, while that of the XG-g-PAA/GO–DCFP composite hydrogel group was 116.79 ± 14.72 mg L⁻¹ h⁻¹, suggesting that the bioavailability of DCFP is greatly enhanced by this composite hydrogel. In conclusion, this study highlights that the XG-g-PAA/GO–DCFP composite hydrogel can be applied as a sustained-release drug carrier.

In this study, graphene oxide (GO) was successfully prepared using the improved Hummers method, and the prepared GO powder was dissolved in distilled water and subjected to ultrasonic stripping.     

Matrix-dispersed magnetic molecularly-imprinted polyaniline for the effective removal of chlorpyrifos pesticide from contaminated water

We report a new adsorbent nanocomposite material based on matrix-dispersed superparamagnetic iron oxide nanoparticles (SPIONs) in molecularly-imprinted polyaniline for the removal of chlorpyrifos (CPF), a hazardous organophosphate pesticide, from water. The synthesized magnetic molecularly-imprinted polymer (MMIP) was characterized by FTIR spectroscopy, XRD, magnetic susceptibility, DLS, zeta potential measurement, SEM and high-resolution TEM imaging. The average size of the naked SPIONs ranges from 15 to 30 nm according to the high-resolution TEM analysis. Moreover, the adsorption kinetics, thermodynamic parameters (ΔG, ΔH and ΔS), adsorption isotherms and rebinding conditions were investigated in detail. The proposed MMIP has an imprinting factor of 1.64. In addition, it showed a high experimental adsorption capacity of 1.77 mg g⁻¹ and a removal efficiency of nearly 80%. The fabricated MMIP material demonstrated excellent magnetic susceptibility allowing for easy separation using an external magnetic field. The adsorption mechanism of CPF onto the MMIP adsorbent followed the second-order kinetics model and fitted to the Temkin adsorption isotherm. By studying the adsorption thermodynamics, negative ΔG values (−1.955 kJ mol⁻¹ at room temperature) were obtained revealing that the adsorption process is spontaneous. Furthermore, the maximum adsorption capacity was obtained at room temperature (ca. 303 K), neutral pH and using a high CPF concentration.

An efficient magnetic molecularly-imprinted polymer adsorbent for removal of chlorpyrifos organophosphate pesticide from water is reported.     

A novel ion-imprinted amidoxime-functionalized UHMWPE fiber based on radiation-induced crosslinking for selective adsorption of uranium

A novel uranium-imprinted adsorbent (AO-Imp fiber) was prepared by radiation-induced crosslinking of amidoxime-functionalized ultra-high molecular weight polyethylene fiber (AO fiber). The porous structure was characterized by scanning electron microscopy (SEM) and positron annihilation lifetime (PAL) spectroscopy after ion imprinting. This ion-imprinted fiber exhibited enhanced adsorption selectivity for uranium in the form of both UO₂²⁻ and [UO₂(CO₃)₃]⁴⁻ in batch experiments. Compared with AO fiber, the adsorption capacity of the AO-Imp(250) fiber for uranium increased from 0.36 mg g⁻¹ to 1.00 mg g⁻¹ in simulated seawater and from 5.02 mg g⁻¹ to 12.03 mg g⁻¹ in simulated acid effluent, while its adsorption capacities for other co-existing metal ions were particularly low. This study provides an approach to prepare ion-imprinted adsorbents without introducing crosslinking reagents, which may be a promising method for uranium extraction.

A novel uranium-imprinted adsorbent (AO-Imp fiber) was prepared by radiation-induced crosslinking of amidoxime-functionalized ultra-high molecular weight polyethylene fiber (AO fiber).     

Adsorption capacity of kelp-like electrospun nanofibers immobilized with bayberry tannin for uranium(vi) extraction from seawater

The extraction of uranium(vi) from seawater is of paramount interest to meet the rapid expansion of global energy needs. A novel gelatin/PVA composite nanofiber band loaded with bayberry tannin (GPNB-BT) was used to extract uranium(vi) from simulated seawater in this study. It was fabricated by electrostatic spinning and crosslinking, and characterized by SEM, EDX, FTIR, and XPS. Batch experiments were carried out to investigate the adsorption of uranium(vi) onto GPNB-BT. Simultaneously, the regeneration–reuse process of the GPNB-BT was determined and illustrated here. The GPNB-BT exhibited excellent adsorption and regeneration performance, and a maximum adsorption capacity of 254.8 mg g⁻¹ toward uranium(vi) was obtained at 298.15 K, pH = 5.5. Further, the regeneration rate for uranium did not decrease significantly after five cycles. Moreover, even at an extremely low initial concentration of 3 μg L⁻¹ in the simulated seawater for 24 h, GPNB-BT showed an ultrahigh adsorption rate of more than 90% and adsorption capacity of 7.2 μg g⁻¹ for uranium. The high density of adjacent phenolic hydroxyl groups and the specific surface area of GPNB-BT improved the adsorption ability of GPNB-BT for uranium. Therefore, the GPNB-BT was shown to have an application prospect for the effective extraction of uranium(vi) from seawater.

A novel kelp-like gelatin/PVA composite nanofiber band loaded with bayberry tannin was fabricated for the extraction of uranium(vi) from seawater.     

Synthesis of hierarchical MgO based on a cotton template and its adsorption properties for efficient treatment of oilfield wastewater

A biomorphic MgO nanomaterial was fabricated via a facile and low-cost immersion method using cotton as the template. The obtained materials were characterized via X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and N₂ adsorption–desorption analysis. The as-prepared MgO retained the structure of cotton, with a porous hierarchical structure and a high specific surface area, which endowed it with great potential due to its excellent adsorption properties for the adsorption of additives in oil field wastewater. It also exhibited the maximum adsorption capacity of 391.36 mg g⁻¹ for sulfonated lignite. The adsorption process of sulfonated lignite on biomorphic MgO was systematically investigated and was found to obey the pseudo-second-order rate equation and the Langmuir adsorption model. The negative values of Gibbs free energy change (ΔG) showed that the adsorption process was feasible and spontaneous. The endothermic process was depicted with a positive value for ΔH.

A biomorphic MgO nanomaterial was fabricated via a facile and low-cost immersion method using cotton as the template.     

Efficient removal of chromate ions from aqueous solution using a highly cost-effective ferric coordinated [3-(2-aminoethylamino)propyl]trimethoxysilane–MCM-41 adsorbent

The present investigation involves synthesis and characterization of MCM-41–AEAPTMS–Fe(iii)Cl using coordinated Fe(iii) on MCM-41–AEAPTMS for efficient removal of hazardous Cr(vi) ions from aqueous solution. The adsorbent MCM-41–AEAPTMS–Fe(iii)Cl was characterized using small-angle X-ray diffraction (SAX), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), Fourier-transform infrared (FT-IR) and Brunauer–Emmett–Teller (BET) surface analyzer techniques. The BET surface area was found to be 87.598 m² g⁻¹. The MCM-41–AEAPTMS–Fe(iii)Cl effectively adsorbs Cr(vi) with an adsorption capacity acquiring the maximum value of 84.9 mg g⁻¹ at pH 3 at 298 K. The data followed pseudo-second-order kinetics and obeyed the Langmuir isotherm model. The thermodynamic data proved the exothermic and spontaneous nature of Cr(vi) ion adsorption on MCM-41–AEAPTMS–Fe(iii). Further, the higher value of ΔH° (−64.339 kJ mol⁻¹) indicated that the adsorption was chemisorption in nature.

The present investigation involves synthesis and characterization of MCM-41–AEAPTMS–Fe(iii)Cl using coordinated Fe(iii) on MCM-41–AEAPTMS for efficient removal of hazardous Cr(vi) ions from aqueous solution.     

Removal of brilliant green dye from synthetic wastewater under batch mode using chemically activated date pit carbon

In this research, a single-stage batch adsorber was designed for removal of brilliant green dye (BG) from aqueous solutions using activated carbon derived from date pits (ADPC) based on the Freundlich isotherm which was the best-fitted isotherm model. Experimental work was carried out within the range of 10–50 ppm initial dye concentration to determine the optimum operating conditions which were 55 min contact time, 0.06 g adsorbent mass, 25 °C, and pH = 8. Process kinetics was best-fitted with the pseudo-second order model, which revealed that the intra-particle diffusion stage is the rate-controlling stage for the process. The process efficiency was assessed by infrared spectroscopy (FTIR), scanning microscopy (SEM), X-ray spectroscopy (EDXS), and Brunauer–Emmett–Teller (BET) where the latter showed that the specific surface area of the adsorbent is 311.38 m² g⁻¹, which gives a favorable maximum monolayer adsorption capacity (77.8 mg g⁻¹). The thermodynamic study proved that BG adsorption on ADPC was physiosorptive (ΔG = −5.86 kJ mol⁻¹) and spontaneous at low temperature (ΔH = −17.7 kJ mol⁻¹, ΔS = −0.04 kJ mol⁻¹ K⁻¹).

In this research, a single-stage batch adsorber was designed for removal of brilliant green dye from aqueous solutions using activated carbon derived from date pits based on the Freundlich isotherm which was the best-fitted isotherm model.     

Synthesis of nano-octahedral MgO via a solvothermal-solid-decomposition method for the removal of methyl orange from aqueous solutions

Nano magnesium oxide has wide applications, and MgO with (111) facets has wider potential applications than MgO with (100) facets (e.g., in catalysis and adsorption). However, nano MgO with (111) polar faces has not been studied throughly, so the preparation of nano-octahedral MgO (N-O-MgO) with eight exposed (111) facets remains a great challenge. Herein, we successfully synthesised N-O-MgO via an effective solvothermal-solid-decomposition method and studied its adsorption performance. The obtained N-O-MgO showed excellent performance (229.36 mg g⁻¹) for methyl orange (MO). The adsorption follows the pseudo-second-order kinetic equation and the Langmuir isotherm model. The dimensionless parameter R_L (0.042) and Gibbs free energy ΔG (−6.538 kJ mol⁻¹) revealed that the adsorption of MO on N-O-MgO was a spontaneous and feasible process. The adsorption of MO and methyl blue (MB) on N-O-MgO were studied to determine the adsorption sites. Based on these experiments and analysis, it was determined that the adsorption sites were magnesium ions and the adsorption mechanism was proposed to describe the adsorption process.

This article reports a facile nano-octahedral MgO synthetic method and its adsorption performance for methyl orange.     

Removal of lithium and uranium from seawater using fly ash and slag generated in the CFBC technology

Fly ash and slag were produced as a result of the incineration of municipal sewage sludge using the circulating fluidized bed combustion (CFBC) technology and were examined for the simultaneous recovery of lithium and uranium from seawater in batch adsorption experiments. These waste materials have been characterized in terms of their physicochemical properties using several research methods including particle size distribution, bulk density, SEM-EDS analysis, thermogravimetry, SEM and TEM morphology, BET, specific surface area, pore volume distribution by the BJH method, ATR FT-IR, and zeta potential. The fly ash and slag waste materials showed the following research results for Li-ion recovery: adsorption efficiency 12.1% and 6.8%, adsorption capacity 0.55 mg g⁻¹ and 0.15 mg g⁻¹, respectively. Better results were reported for U ion recovery: adsorption efficiency 98.4% and 99.9%, adsorption capacity 21.3 mg g⁻¹ and 56.7 mg g⁻¹ for fly ash and slag, respectively. In conclusion, the conducted research revealed that CFBC fly ash and slag are promising low-cost adsorbents for the effective recovery of Li and U ions from seawater.

Fly ash and slag were produced as a result of the incineration of municipal sewage sludge using the circulating fluidized bed combustion (CFBC) technology and were examined for the simultaneous recovery of lithium and uranium from seawater in batch adsorption experiments.     

Thermodynamic study of the adsorption of acridinium derivatives on the clay surface

In this study, the adsorption behavior of mono-cationic acridinium derivatives on a synthetic clay mineral (Sumecton SA) was investigated. The acridinium derivatives were adsorbed on the clay surface without aggregation, as found from the changes in the absorption spectra of the acridinium derivatives with SSA and without SSA represented by two-component equilibrium systems of adsorbed and non-adsorbed components. Following the Langmuir isotherm analysis, the adsorption equilibrium constants and maximum adsorption amounts were determined for acridinium derivatives, and the Gibbs free energy change (ΔG) was calculated to be in the range of −33.8 to 40.0 kJ mol⁻¹ from the adsorption equilibrium constants. These results indicated that the adsorption of acridinium derivatives on the clay surface was an exergonic reaction. Moreover, thermodynamic parameters such as enthalpy change (ΔH) and entropy change (ΔS) were obtained from the temperature effect experiments. For all acridinium derivatives, ΔH (from −7.82 to −26.0 kJ mol⁻¹) and ΔS (0.047–0.088 kJ mol⁻¹ K⁻¹) were found to be negative and positive, respectively. It was suggested that not only electrostatic interactions, but also van der Waals forces and hydrophobic interactions played an important role in the adsorption of cationic aromatic molecules on the clay surface. Because these thermodynamic parameters showed a strong correlation with the molecular cross-sectional area of acridinium derivatives, it was suggested that the contribution of hydrophobic interactions became smaller as the molecular cross-sectional area became larger.

Thermodynamic studies indicate that van der Waals and hydrophobic interactions contribute to the adsorption of mono-cationic acridinium derivatives on the clay surface.     

Mesoporous-rich calcium and potassium-activated carbons prepared from degreased spent coffee grounds for efficient removal of MnO42− in aqueous media

Commercial ACs typically possess high surface areas and high microporosity. However, ACs with appreciable mesoporosity are growing in consideration and demand because they are beneficial for the adsorption of large species, such as heavy metal ions. Thus, in this study, degreased coffee grounds (DCG) were used as precursors for the production of ACs by means of chemical activation at 600 °C for the efficient removal of manganese in the form of MnO₄²⁻. One of the most common activating agents, ZnCl₂, is replaced by benign and sustainable CaCl₂ and K₂CO₃. Three ratios 1 : 1, 1 : 0.5 and 1 : 0.1 of precursor-to-activating agent (g g⁻¹) were investigated. Porosimetry indicates 1 : 1 CaCl₂ DCGAC is highly mesoporous (mesopore volume 0.469 cm³ g⁻¹). CaCl₂ DCGAC and K₂CO₃ DCGAC shows high adsorption capacities of 0.494 g g⁻¹ and 0.423 g g⁻¹, respectively for the uptake of MnO₄²⁻ in aqueous media. The adsorption process follows pseudo-second order kinetics inline with the Freundlich isotherm (R² > 0.9). Thermodynamic data revealed negative values of ΔG (approx −0.1751 kJ mol⁻¹) demonstrating that the adsorption process on 1 : 1 CaCl₂DCGAC was spontaneous.

Spent coffee grounds are an interesting high volume renewable resource for valorisation. Activation with CaCl₂ produces mesoporous carbons with high capacity for removal of MnO₄²⁻.     

Facile preparation of low-cost HKUST-1 with lattice vacancies and high-efficiency adsorption for uranium

In this work, we prepared HKUST-1 and HKUST-1 with lattice vacancies (HLV) using benzoic acid (BA) as a low-cost modulator to replace part of the traditional trimesic acid ligand (H₃BTC). The structure and morphology of the products were characterized by FTIR, XRD, SEM and XPS. The adsorption performance of the products for uranium from aqueous solutions was investigated. The results showed that the sorption of U(vi) on HKUST-1 and HLV agreed with the Langmuir isotherm model (R_HKUST-1² = 0.9867 and R_HLV² = 0.9828) and the maximum adsorption capacity was 430.98 mg g⁻¹ and 424.88 mg g⁻¹, respectively. According to kinetics studies, the adsorption fitted better with a pseudo-second-order model (R_HKUST-1² = 1.0000 and R_HLV² = 0.9978). The as-prepared adsorbents were used for the removal of uranium from real water samples as well. The results showed that HLV with lower cost is a promising adsorbent for uranium from aqueous solutions.

HLV was prepared using benzoic acid with lower cost as the modulator to replace part of the traditional ligand H₃BTC for uranium removal.     

Aqueous carbofuran removal using slow pyrolyzed sugarcane bagasse biochar: equilibrium and fixed-bed studies

Herein, biochar was produced by the slow pyrolysis of sugarcane bagasse at 500 °C in absence of oxygen. The resulting sugarcane bagasse biochar (SB500) was characterized and used for aqueous carbofuran sorptive removal. Batch carbofuran sorption studies were accomplished to ascertain the influence of solution pH, contact time, temperature (25, 35 and 45 °C) and adsorbate/adsorbent concentration. SB500 adsorbed more carbofuran at low pH values and less carbofuran at high pH values. The necessary sorption equilibrium, kinetic and thermodynamic parameters were determined. The equilibrium isotherm data were fitted to the Freundlich, Langmuir and Temkin models. The Langmuir equation best fitted the experimental sorption data. The maximum Langmuir adsorption capacity of 18.9 mg g⁻¹ was obtained at pH 6.0 and 45 °C. The enthalpy change (ΔH°), entropy change (ΔS°) and Gibbs free energy (ΔG°) were evaluated. The fixed-bed carbofuran sorption studies were carried out using the optimum parameters determined via the batch studies. The necessary fixed-bed design parameters were obtained. Carbofuran desorption and SB500 regeneration were successfully achieved. About 96% of the total carbofuran was successfully desorbed from the exhausted biochar using 20 mL ethanol in 10 mL increments. Moreover, a possible carbofuran adsorption mechanism has been proposed. A number of interactions including (1) hydrogen bonding of the protonated and neutral carbofuran to biochar, (2) carbofuran sorption onto biochar via π–π electron donor–acceptor interactions and (3) carbofuran diffusion into the biochar pores were considered to explain the sorption mechanism. The batch and fixed-bed sorption results demonstrate that the sugarcane bagasse biochar (SB500) can be effectively used for the sustainable removal and recovery of carbofuran from water.

Sugarcane bagasse biochar was prepared, characterized and used for aqueous carbofuran removal. Sorption equilibrium and dynamics studies were carried out. An adsorption capacity of 19 mg g⁻¹ was obtained at 45 °C. Carbofuran adsorption mechanism has been proposed.     

Zwitterionic superabsorbent polymer hydrogels for efficient and selective removal of organic dyes

A novel zwitterionic superabsorbent polymer hydrogel [ZI-SAH] was synthesized by free radical polymerization and used for the removal of crystal violet (CV) and congo red (CR) from an aqueous medium. ZI-SAH was composed of pH-sensitive monomers poly(3-acrylamidopropyl) trimethylammoniumchloride (APTMACl) and 2-acrylamido-2-methylpropanesulphonic acid (AAMPSA). The hydrogel was characterized by SEM and FT-IR spectroscopy, while the visco-elastic behavior was studied using rheological tests. The hydrogel showed a point of zero charge (PZC) at pH 7.2 and high swelling abilities of 3715% at pH 9 and 3112% at pH 5. The cationic crystal violet (CV) and anionic congo red (CR) dyes were employed to investigate the removal ability of ZI-SAH using the batch adsorption method. The materials became more selective towards oppositely charged dyes at pH 5 and 9. The effects of parameters such as contact time, initial concentration of dyes, pH, ZI-SAH dosage and ionic strength on the removal performance were investigated. A kinetic study was carried out via Lagergren pseudo first order and pseudo second order kinetics. The adsorption efficiencies of ZI-SAH were 13.6 mg g⁻¹ for CV and 9.07 mg g⁻¹ for CR with % removal values of 97 and 89, respectively. The thermodynamic parameters, namely, ΔG°, ΔH° and ΔS° were determined, and the negative value of free energy showed that the process of adsorption was spontaneous. ZI-SAH was recycled and reused in five consecutive cycles with removal efficiency > 75%.

A novel zwitterionic superabsorbent polymer hydrogel [ZI-SAH] was synthesized by free radical polymerization and used for the removal of crystal violet (CV) and congo red (CR) from an aqueous medium.     

Tinospora cordifolia derived biomass functionalized ZnO particles for effective removal of lead(ii), iron(iii), phosphate and arsenic(iii) from water

Owing to the vast diversity in functional groups and cost effectiveness, biomass can be used for various applications. In the present study, biomass from Tinospora cordifolia (TnC) was prepared and grafted onto the surface of ZnO particles following a simple method. The TnC functionalized ZnO particles (ZnO@TnC) were characterized and exhibited excellent adsorption properties towards Pb²⁺ (506 mg g⁻¹), Fe³⁺ (358 mg g⁻¹) and PO₄³⁻ (1606 mg g⁻¹) and the Fe³⁺ adsorbed ZnO@TnC adsorbs AsO₂¹⁻ (189 mg g⁻¹); the metal ions and anions were analyzed by ICP and IC. For reuse of ZnO@TnC, a desorption study was successfully carried out using NaOH and EDTA for PO₄³⁻ and Pb²⁺, respectively; Fe³⁺ was further used for adsorption of As(iii). The adsorption fits well with the Langmuir adsorption isotherm model and the adsorption kinetic data are best fitted with a pseudo-second-order equation. The system developed may be useful for treatment of waste water and industrial effluents.

Owing to the vast diversity in functional groups and cost effectiveness, biomass can be used for various applications.     

Selective preconcentration separation of Hg(ii) and Cd(ii) from water,fish muscles,and cucumber samples using recycled aluminum adsorbents

Modified aluminum scrap waste was used in the selective extraction of Hg(ii), and Cd(ii) ions. The aluminum scraps were modified with dibenzoylmethane, or isatoic anhydride, or 5-(2-chloroacetamide)-2-hydroxybenzoic acid. The modified aluminum sorbents were characterized by FT-IR, SEM, XRD, XPS, TGA, and elemental analysis. Modes of chelation between adsorbents and target metal ions were deduced via DFT. The highest adsorption capacity was observed for benzo-amino aluminum (BAA) toward Hg(ii), which reached 234.56 mg g⁻¹, while other modified sorbents ranged from 135.28 mg g⁻¹ to 229.3 mg g⁻¹. Under the optimized conditions, the BAA adsorbent showed a lower limit of detection (1.1 mg L⁻¹) and limit of quantification (3.66 mg L⁻¹) for mercury ions than other sorbents. The prepared aluminum adsorbents also exhibited significant selectivities for Hg(ii) and Cd(ii) ions in the presence of competing metal ions.

Modified aluminum scrap waste was used in the selective extraction of Hg(ii), and Cd(ii) ions.