Surface magnetization of hydrolyzed Luffa Cylindrica biowaste with cobalt ferrite nanoparticles for facile Ni2+ removal from wastewater

Hydrothermal and NaOH-treated rice straw fibre: A potential lignocellulosic biosorbent material for removal of textile dyes from contaminated industrial wastewater

This study assessed lignocellulosic rice straw fibres as a potential biosorbent for removing textile dyes from industrial effluents. Fibre extraction was performed via hydrothermal pre-treatment and pulping using dilute NaOH. The adsorption capacity of the biosorbent was tested on carcinogenic dyes, including malachite green (MG), methylene blue (MB), basic fuchsin (BF), and Congo red (CR). Characterization techniques included gravimetric composition analysis, Fourier-Transform Infrared (FTIR) Spectroscopy, High-Resolution X-ray diffraction (HR-XRD), Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (FESEM-EDS), Brunauer-Emmett-Teller (BET) analysis and determination of the point of zero charge (pzc). It was found that the maximum removal efficiencies for cationic dyes (MG, MB, and BF) were 88.7 %, 87.5 %, and 82.87 %, respectively, under optimal conditions with a biosorbent dosage of 2 g L-1, a temperature of 28 °C, an initial dye concentration of 25 mg L-1, and a contact time of 120 min, with an optimal pH range of 4-7. Adsorption data followed the Langmuir isotherm model and pseudo-second-order kinetics. For the anionic dye CR, adsorption efficiency was limited to 22.2 %, achieved at pH 1 with a biosorbent dosage of 1 g L-1, a temperature of 28 °C, and a contact time of 90 min, conforming to the Temkin isotherm and pseudo-second-order kinetics. These findings demonstrate that rice straw fibres can serve as a cost-effective and eco-friendly biosorbent for cationic dye removal, offering a sustainable approach to mitigate textile dye pollution while addressing environmental concerns associated with rice straw residue burning, thereby adding value to this abundant agricultural byproduct.

Enhancing fluoride ion removal from aqueous solutions and glass manufacturing wastewater using modified orange peel biochar magnetic composite with MIL-53

In this study, we developed new adsorbents derived from orange peel biochar (BCOP) and enhanced them with CoFe2O4 magnetic nanoparticles (BCOP/CoFe2O4) and MIL-53(Al) (BCOP/CoFe2O4/MIL-53(Al)). These adsorbents were utilized to remove fluoride (FL) ions from aqueous solutions. We analyzed the properties of these adsorbents using a range of techniques, including FTIR, XRD, SEM, EDX-Map, VSM, Raman spectroscopy, and BET. Our findings indicate that the components interact effectively with one another. Specifically, the BCOP/CoFe2O4/MIL-53(Al) sample exhibited a specific surface area of 196.430 m2/g and a magnetic saturation value of 9.704 emu/g. The maximum FL ion adsorption capacities for BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) were 7.618, 16.330, and 37.320 mg/g, respectively, indicating that the modifications significantly enhanced the adsorption capacity. The optimum fluoride ion removal rates using BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) were 97.88%, 98.23%, and 99.06%, respectively, at adsorbent doses of 2.5, 1.5, and 0.8 g/L, contact times of 90, 70, and 50 min, pH 4, temperature 50 °C, and a FL concentration of 10 mg/L. Thermodynamic studies revealed that the adsorption process was spontaneous and endothermic, with increased randomness between the adsorbent and fluoride ions. Kinetic analyses showed that fluoride ion adsorption by BCOP/CoFe2O4/MIL-53(Al) followed a pseudo-second-order (PSO) model, while BCOP and BCOP/CoFe2O4 followed a pseudo-first-order (PFO) model. Additionally, the equilibrium data for fluoride ion adsorption on BCOP/CoFe2O4/MIL-53(Al) adhered to the Freundlich model, whereas the other samples conformed to the Langmuir model. The study evaluates the effectiveness of BCOP, BCOP/CoFe2O4, and BCOP/CoFe2O4/MIL-53(Al) in removing FL ions from glass manufacturing wastewater, highlighting the superior performance of the magnetic composite due to its enhanced surface area and functional groups. Notably, the adsorbents demonstrated good regenerative capabilities, maintaining high performance over multiple adsorption cycles.

Efficiency of chemically activated raw and calcined waste fish bone for adsorption of Cd (II) and Pb (II) from polluted water

Bone biochar is used as an adsorbent in water pollution control because of its high surface area and pore volumes. This study is attempting to prepare a low-cost adsorbent from waste fish bones by chemical activation and use it for the removal of Cd2+ and Pb2+ from polluted water. The preparation of fish bone adsorbents involved two methods. The first method includes the chemical activation of waste fish bone using different chemical activators (0.001 M HNO3, 0.1 M NaOH, 0.5% H2O2, and ethanol) (FB), while the second one includes the calcination of waste fish bone after the chemical activation at 873 K (FB-Hy). The synthesized fish bone adsorbent (FB) was characterized by electron microscopy (SEM), X-ray diffractometer (XRD), X-ray fluorescence (XRF), Brunauer–Emmett–Teller (BET) surface area, and Fourier transform infrared (FT-IR). The effectiveness of the prepared adsorbent (FB) in removing Pb and Cd was evaluated based on contact time, solution pH, solution temperature, initial metal concentration, and adsorbent dose. Metal concentrations were measured by atomic absorption spectroscopy. The results show that 0.1 M NaOH activation of bone waste (FB) is suitable for higher adsorption of Cd2+ and Pb2+ compared with other activators. The maximum adsorption of Pb and Cd with the FB adsorbent was 99.74 and 99.35%, respectively, at optimum conditions (pH 6.0, contact time 30 min, initial metal concentration 10 ppm, adsorbent dosage 0.1 g, and temperature at 328 K). The results of kinetic adsorption obeyed a pseudo-second-order model. Freundlich and Langmuir isotherms were applied, and the adsorption was found to fit well with the Langmuir model. This study ended with the success of preparing an eco-friendly and low-cost fish bone adsorbent from the waste fish bone and using it for the removal of Cd2+ and Pb2+ from polluted water.

Removal of As(V) and Cr(VI) using quinoxaline chitosan schiff base: synthesis, characterization and adsorption mechanism

Elevated Arsenic and Chromium levels in surface and ground waters are a significant health concern in several parts of the world. Chitosan quinoxaline Schiff base (CsQ) and cross-linked chitosan quinoxaline Schiff base (CsQG) were prepared to adsorb both Arsenate [As(V)] and Chromium [Cr(VI)] ions. The thermo-gravimetric analysis (TGA), X-ray diffraction analysis (XRD), and Fourier-transform infrared spectroscopy (FTIR) were used to investigate the prepared Schiff bases (CsQ) and (CsQG). The UV-VIS spectra showed a shift in the wavelength area of the modified polymer, indicating the reaction occurrence, besides the variation of the shape and intensity of the peaks. The XRD patterns showed the incensement of the amorphous characteristic. On the other hand, the thermal stability of the modified polymers is better according to TGA studies; also, the morphology of the modified chitosan was investigated before and after crosslinking (CsQ and CsQG) using a scanning electron microscope (SEM) where the surface was fall of wrinkles and pores, which then were decreased after cross-linking. Contact time, temperature, pH, and initial metal ion concentration were all studied as factors influencing metal ion uptake behavior. The Langmuir, Temkin, Dubinin-Radushkevich, and Freundlich isotherm models were used to describe the equilibrium data using metal concentrations of 10-1000 mg/L at pH = 7 and 1 g of adsorbent. The pseudo-first-order and pseudo-second-order kinetic parameters were evaluated. The experimental data revealed that the adsorption kinetics follow the mechanism of the pseudo-second-order equation with R2 values (0.9969, 0.9061) in case of using CsQ and R2 values (0.9989, 0.9999) in case of using CsQG, demonstrating chemical sorption is the rate-limiting step of the adsorption mechanism. Comparing the adsorption efficiency of the synthesized Schiff base and the cross-linked one, it was found that CsQ is a better adsorbent than CsQG in both cases of As(V) and Cr(VI) removal. This means that cross-linking doesn't enhance the efficiency as expected, but on the contrary, in some cases, it decreases the removal. In addition, the newly modified chitosan polymers work better in As(V) removal than Cr(VI); the removal is 22.33% for Cr(VI) and 98.36% for As(V) using CsQ polymer, whereas using CsQG, the values are 6.20% and 91.75% respectively. On the other hand, the maximum adsorption capacity (Qm) for As(V) and Cr(VI) are 8.811 and 3.003 mg/g, respectively, using CsQ, while in the case of using CsQG, the Qm value reaches 31.95 mg/g for As(V), and 103.09 mg/g for Cr(VI).

Functionalization strategy of carboxymethyl cotton gauze fabrics with zeolitic imidazolate framework-67 (ZIF-67) as a recyclable material for biomedical applications

The accumulation of uremic toxins in the human body poses a deadly risk because it causes chronic kidney disease. To increase the effectiveness of hemodialysis and raise the survival rate, these toxins must be effectively removed from the bloodstream. Developing effective materials for removing these dangerous substances requires a thorough understanding of the interactions between an adsorbent and the uremic toxins. Thankfully, metal-organic frameworks (MOFs) have shown considerable promise for the identification and treatment of kidney disorders. Herein, cotton gauze fabrics (CGF) were carboxylated using monochloroacetic acid to produce carboxymethylated cotton gauze fabrics (CM-CGF). CM-CGF was subsequently decorated in situ with zeolitic imidazolate framework-67, resulting in carboxymethylated cotton gauze fabrics-zeolitic imidazolate framework-67 (CM-CGF-ZIF). The CGF, CM-CGF, and CM-CGF-ZIF were evaluated for potential kidney applications by removing uric acid and creatinine from mimic blood. The results showed that CM-CGF-ZIF had the highest adsorption of uric acid and creatinine. The maximum adsorption capacity of uric acid and creatinine was 164 and 222 mg/g for CM-CGF-ZIF, respectively, compared to 45 and 67 mg/g for CGF. CM-CGF-ZIF showed excellent antibacterial activity, good antifungal activity, low cytotoxicity, and a satisfactory level of blood compatibility.

Biosorption of cobalt and chromium from wastewater using manganese dioxide and iron oxide nanoparticles loaded on cellulose-based biochar: Modeling and optimization with machine learning (artificial neural network)

In this study, two nanomaterials with excellent adsorption capacities were developed to remove heavy metals efficiently from wastewater. Manganese dioxide MnO2 nanoparticles and iron oxide Fe2O3 nanoparticles were successfully synthesized using cassava peel carbon and characterized by different techniques. The experimental tests for the adsorption process were done in a batch system, and the influence of various parameters such as temperature (from 5 to 60 °C), initial concentration (from 10 to 60 mg/L), pH (2 to 8), and contact time (5 to 180 min) on the biosorption of cobalt (II) and chromium (VI) were fully investigated. Furthermore, the Qmax were 546.32 mg/g and 349.59 mg/g for chromium (VI) and cobalt (II) respectively. The results fitted Langmuir with the pseudo-second-order model, revealing that chemisorption controls heavy metals removal, while the thermodynamic sorption was an endothermic and spontaneous reaction. Artificial Neural Network (ANN) model was developed to predict as well as to simulate the experimental results, for this purpose, the proposed model was based on five independent inputs or variables and one output or response which is the predicted adsorbed amount, the proposed ANN model showed an appreciable prediction accuracy with high optimization ability for chromium (VI) and cobalt (II) removal.

Utilization of peanut hull hydrochar /beta cyclodextrin/Fe3O4 magnetic composite for lead ion removal from water solution

This study involves synthesizing peanut hull hydrochar (PHH) and a PHH/β-CD/Fe3O4 magnetic composite through hydrothermal and chemical precipitation methods, respectively, to use as effective adsorbents for Pb2+ removal. Vibrating-sample magnetometry (VSM) and Brunauer-Emmett-Teller (BET) analyses revealed that the magnetic saturation value and specific active surface area of PHH/β-CD/Fe3O4 are 31.543 emu/g and 32.123 m2/g, respectively. The impact of key variables on adsorption efficiency was evaluated using the response surface method - central composite design. ANOVA results (F-value: 166.22 and p-value: <0.05) demonstrated that the model effectively assesses the interaction of variables in the adsorption process. Additionally, R2, Adjusted R2, and Predicted R2 values were 0.999, 0.986, and 0.975, respectively, indicating the model's high adequacy in describing response changes. The maximum efficiency for Pb2+ adsorption was found to be 95.35% using PHH and 99.73% with the PHH/β-CD/Fe3O4 magnetic composite. These measurements were taken at a temperature of 25 °C, an adsorbent dose of 1 g/L, a pH of 6, and a Pb2+ concentration of 5 mg/L, with respective contact times of 130 min and 50 min. Thermodynamic analysis revealed negative enthalpy and Gibbs free energy values, indicating that the adsorption process is exothermic and spontaneous. The negative entropy parameter suggests a reduction in random interactions during the process. The Pb2+ adsorption data for both PHH (R2: 0.982) and PHH/β-CD/Fe3O4 (R2: 0.985) were best described by the Pseudo 2nd order kinetic model. Equilibrium data followed the Freundlich model, with R2 values of 0.981 for PHH and 0.990 for PHH/β-CD/Fe3O4, highlighting the importance of heterogeneous surfaces in the removal process. The maximum adsorption capacities for Pb2+ were 26.72 mg/g for PHH and 33.88 mg/g for PHH/β-CD/Fe3O4. Reuse and stability tests confirmed the structural stability and reusability of the adsorbents. Therefore, the PHH/β-CD/Fe3O4 magnetic composite is a promising option for removing Pb2+ from aqueous solutions.

Evaluation, optimization study, and life cycle assessment of novel eco-friendly PVA-based nanocomposite hydrogel adsorbents for methylene blue and paracetamol removal

In this study, an eco-friendly and novel hydrogel based on a crosslinked polyvinyl alcohol (PVA), iota carrageenan (IC) and polyvinylpyrrolidone (PVP) scaffold, containing a large amount (10-50 wt%) of nanoscale palm fronds (NPF) as additives, for water purification was demonstrated. A life cycle assessment (LCA) findings on NPF as biomass waste incorporated into PVA_PVP_IC polymer matrix was presented, and the results highlight the necessity of focused actions to reduce environmental impact and support the palm waste utilization in a sustainable manner. The multicomponent nanocomposite hydrogels were examined as adsorbents in a system work in batches for methylene blue (MB) and paracetamol (PCT) removal. The results show that, the presence of NPF, which dispersed in the hydrogel PVA_PVP_IC scaffolds containing both covalent and non-covalent cross-linking bonds, greatly enhanced the MB and PCT adsorption efficiency. A response surface methodology (RSM) model was used to find the best operating parameters of contaminant adsorption, including time, adsorbent dose, and starting concentration of pollutants. By using this statistical model, it was found that the optimal conditions for the adsorption reaction to achieve the complete removal of MB are 66.7 h adsorption time duration, 98.5 mg L-1 starting concentration, and an adsorbent dose of 5.9 mg, while for the complete removal of PCT, it is 57.6 h adsorption time duration, 80 mg L-1 starting concentration, and an adsorbent dose of 6 mg. The reusability of the nanocomposite hydrogels were tested for 5 cycles, all showed high adsorption capacity, indicating the potential for practical application of this nanocomposite hydrogel system. This study indicates that the prepared nanocomposite hydrogel raises the standard used for treatment of wastewater and also gives a solution to protect the environment and mitigate global warming.

Synthesis of a nitrogen-rich dendrimer grafted on magnetic nanoparticles for efficient removal of Pb(ii) and Cd(ii) ions

Rapid industrialization, urbanization, and human activities in catchments have presented a significant global challenge in removing heavy metal contaminants from wastewater. Here, a study was conducted to synthesize a nano-magnetic dendrimer based on a trimesoyl core that can be easily separated from the environment using an external magnet (Fe3O4@NR-TMD-G1, Fe3O4@NR-TMD-G2). The synthesized structure was characterized using various conventional techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), powder X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), and Brunauer-Emmett-Teller surface area analysis (BET). The prepared adsorbent showed good binding ability and excellent adsorption efficiency toward Pb(ii) and Cd(ii) metal ions from aqueous media (98.5%, 93.6%). The effect of different conditions including pH, adsorbate concentration, adsorbent dosage, isotherm, kinetics, and adsorption mechanism was considered. The highest adsorption efficiency was achieved at 25 °C and pH 4 using 0.08 g of Fe3O4@NR-TMD-G1, within 25 minutes for Pb(ii) and 120 minutes for Cd(ii), respectively. Batch adsorption experiments revealed that Fe3O4@NR-TMD-G1 was more effective in removing Pb(ii) and Cd(ii) compared to Fe3O4@NR-TMD-G2, with maximum capacities of 130.2 mg g-1 and 57 mg g-1, respectively. The adsorption process followed the Langmuir isotherm with a high correlation coefficient (R 2 = 0.9952, 0.9817) and non-linear pseudo-second-order kinetic model. Density functional theory (DFT) analysis indicated that the adsorbent transferred electrons to Pb(ii) and Cd(ii), forming stable chelates on the nanostructure surface. The heavy metal ions could be adsorbed by coordination to the heteroatoms of the nanostructure and also by electrostatic interactions. The recycled hybrid nanomaterial was dried and applied to different adsorption-desorption tests and the desorption efficiency was found to be 98%. So, the newly synthesized dendritic magnetic nanostructure demonstrated significant potential in efficient removal of metal ions from water and wastewater, highlighting its importance in addressing the global challenge of heavy metal contamination.

Magnetic hybrid spheres of glauconite/calcium alginate interface for methylene blue adsorption: Synthesis, characterization, and novel physicochemical insights through theoretical treatment

Fe3O4 nanoparticles were embedded within a glauconite‑calcium alginate (G/CA) matrix to create magnetic hybrid spheres (MNPs-G/CA), with the aim of purifying water from methylene blue (MB) at temperatures of 25, 40, and 50 °C. MNPs-G/CA adsorbent was characterized using numerous techniques, including elemental mapping, zeta potential, FTIR, FESEM, XRD, EDX, and TEM. The greatest amount of the removed MB was achieved under definite conditions of solution pH 8.0, MNPs-G/CA mass (25 mg), interaction time (2 h), and 200 mg/L of MB concentration. The MB uptake process kinetic followed a pseudo-second-order equation (R2 > 0.99) at all tested temperatures. The equilibrium data were fitted to a statistical physics multilayer model in conjunction with the Langmuir and Freundlich equations. The steric n parameter reveals that MNPs-G/CA adsorbent possesses a mixed adsorption orientation (i.e., ranging from 0.69 to 0.93) across various temperatures. The amount of MNPs-G/CA active positions (the NM parameter) was progressively increased from 245 mg/g to 419 mg/g. The measured adsorption capacities (Qsat) ranged from 466.49 to 664.37 mg/g, and the removal of MB molecules was consistent with an endothermic interaction. The interface between the MNPs-G/CA-MB was principally dictated by electrostatic attractions, as evidenced by the values of adsorption energies (∆E), which varied from 16.75 to 21.52 kJ/mol. The regenerated MNPs-G/CA offered over 80 % of its adsorption strength after the fourth adsorption-desorption cycle. This study contributes to our understanding of the physicochemical parameters controlling the MB adsorption mechanism on multifunctional hybrid adsorbents, like the interface between glauconite, alginate, and MNPs.

High removal of methylene blue and methyl violet dyes from aqueous solutions using efficient biomaterial byproduct

Dyes are among the toxic contaminants that significantly impact water ecosystems. A biomaterial prepared from Zizyphus Spina-Christi seed (ZSCS) to remove methylene blue (MB) and methyl violet (MV) from an aqueous solution was investigated. Several techniques have been used, including FTIR, SEM, EDX, XPS, and TGA, to characterize the physical and chemical properties of ZSCS. The effect of various parameters such as pH, adsorbent dosage, contact time, temperature, and initial dye concentration on the adsorption process were studied. The ZSCS adsorbent showed efficient MB and MV dye adsorption with Langmuir adsorption capacity of 666.66 and 476.19 mg/g, respectively, at experimental condition [(pH = 6; time = 30 min; T = 45 °C, dye concentration: 500 mg/L, and adsorbent dose = 0.6 g/L for MB and 1 g/L for MV dye)]. Kinetic and isotherm models were applied to fit the experimental outcomes. The result showed that ZSCS showed an ultrafast absorption process with a high removal efficiency of MB and MV within 5 min indicating its effective adsorption properties. The Langmuir isotherm model was the most suitable model for describing the adsorption of MB and MV dyes on ZSCS. The pseudo-second-order model kinetic fits better to MB and MV adsorption onto ZSCS than other models, suggesting that the adsorption mechanism followed chemisorption. Our results could offer an efficient cost-effective approach for dye removal from wastewater.

Sodium alginate-encapsulated nano-iron oxide coupled with copper-based MOFs (Cu-BTC@Alg/Fe3O4): Versatile composites for eco-friendly and effective elimination of Rhodamine B dye in wastewater purification

This study explores the effectiveness of Alginate-coated nano‑iron oxide combined with copper-based MOFs (Cu-BTC@Alg/Fe3O4) composites for the sustainable and efficient removal of Rhodamine B (RhB) dye from wastewater through adsorption and photocatalysis. Utilizing various characterization techniques such as FTIR, XRD, SEM, and TEM, we confirmed the optimal synthesis of this composite. The composites exhibit a significant surface area of approximately 160 m2 g-1, as revealed by BET analysis, resulting in an impressive adsorption capacity of 200 mg g-1 and a removal efficiency of 97 %. Moreover, their photocatalytic activity is highly effective, producing environmentally friendly degradation byproducts, thus underlining the sustainability of Cu-BTC@Alg/Fe3O4 composites in dye removal applications. Our investigation delves into kinetics and thermodynamics, revealing a complex adsorption mechanism influenced by both chemisorption and physisorption. Notably, the adsorption kinetics indicate equilibrium attainment within 100 min across all initial concentrations, with the pseudo-second-order kinetic model fitting the data best (R2 ≈ 0.999). Furthermore, adsorption isotherm models, including Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich, elucidate the adsorption behavior, with the Temkin and Dubinin-Radushkevich models showing superior accuracy compared to the Langmuir model (R2 ≈ 0.98 and R2 ≈ 0.96, respectively). Additionally, thermodynamic analysis reveals a negative Gibbs free energy value (-6.40 kJ mol-1), indicating the spontaneity of the adsorption process, along with positive enthalpy (+24.3 kJ mol-1) and entropy (+82.06 kJ mol-1 K) values, suggesting an endothermic and disorderly process at the interface. Our comprehensive investigation provides insights into the optimal conditions for RhB adsorption onto Cu-BTC@Alg/Fe3O4 composites, highlighting their potential in wastewater treatment applications.

Effectiveness of polyacrylamide-g-gelatin/ACL/Mg-Fe LDH composite hydrogel as an eliminator of crystal violet dye

Cationic synthetic dyes are one of the hazards in aqueous solutions that can affect the health of humans and living organisms. In the current work, polyacrylamide (PAM)-g-gelatin hydrogel and modified PAM-g-gelatin hydrogel using activated carbon of Luffa cylindrica (ACL) and ACL/Mg-Fe LDH were applied to eliminate crystal violet (CV), a cationic dye, from water media. The hydrogels were synthesized using free radical polymerization approach, and the hydrogels were characterized using FTIR, XRD, TGA-DTG, BET, SEM, and EDX-Map. The surface area of ACL, ACL/Mg-Fe LDH, PAM-g-gelatin, PAM-g-gelatin/ACL, and PAM-g-gelatin/ACL/Mg-Fe LDH were 99.71, 141.99, 0.74, 1.47, and 1.65 m2/g, respectively, which shows that the presence of ACL and ACL/Mg-Fe LDH improved the area of the hydrogels. The maximum abatement of CV using PAM-g-gelatin (92.81%), PAM-g-gelatin/ACL (95.71%), and PAM-g-gelatin/ACL/Mg-Fe LDH (98.25%) was obtained at pH=9, temperature 25 °C, 10 mg/L CV, 60 min time, and adsorber dose of 2 g/L (for PAM-g-gelatin) and 1.5 g/L (other samples). The value of thermodynamic factors confirmed that the abatement process is exothermic and spontaneous. The kinetics data followed the pseudo-second kinetic (PSO) model. The Langmuir isotherm model had a more remarkable ability to describe the equilibrium data. The maximum adsorption capacity for PAM-g-gelatin, PAM-g-gelatin/ACL, and PAM-g-gelatin/ACL/Mg-Fe LDH was determined 35.45, 39.865, and 44.952 mg/g, respectively. Generally, the studied hydrogels can eliminate dyes from wastewater and be used as effective adsorbers.

Preparation and characterization of CS/PAT/ MWCNT@MgAl-LDHs nanocomposite for Cd2+ removal and 4-nitrophenol reduction

The present study evaluated the performance of multiwalled carbon nanotube (MWCNT)@MgAl-layered double hydroxide (LDH) nanoparticles loaded on poly-2 aminothiazole (PAT)/chitosan (CS) matrix (CPML) to remove Cd2+ ions from aqueous solution. The removal efficiency of modified CS/PAT with MWCNT@MgAl-LDHs was increased significantly compared to pure CS/PAT. The influence of heavy metal ion concentration, pH, temperature, adsorbent dosage, and contact time on the adsorption was examined. The optimum conditions for the adsorption of Cd2+ ions were 25 0C with the adsorbent dosage of 0.06 g and initial concentration for adsorption of the Cd2+ 100 mg/L at pH = 8. The maximum adsorption capacity was measured to be 1106.19 mg/g. The values of thermodynamic parameters namely Gibbs free energy (ΔG°), entropy change (ΔS°), and enthalpy change (ΔH°) indicated the feasibility, spontaneity and the endothermic nature of the adsorption process, respectively. The pseudo-second-order kinetics and the Langmuir model were selected as the best models for the adsorption process. Also, CPML nanocomposite (NC) was successfully tested for p-nitrophenol (p-NP) reduction in the presence of NaBH4. The reaction was nearly completed in 6 min. The fabricated CPML-NC could be reused for three consecutive cycles.

Photocatalytic activity of ZnO doped Nano hydroxyapatite/GO derived from waste oyster shells for removal of Methylene blue

Hydroxyapatite (HAp) stands as an inorganic compound, recognized as a non-toxic, bioactive ceramic, and its composition closely resembles that of bone material. In this study, nHAp was prepared from waste oyster shells, which are biowaste rich in calcium carbonate. nHAp with its unique catalytic property can be used as an adsorbent in various fields, including wastewater treatment. nHAp with an exceptional surface adsorbent with excellent chemical stability, enabling its catalytic function. Nano hydroxyapatite doped with Zinc oxide (ZnO) by wet chemical precipitation and made into a composite with Graphene oxide (GO) by modified hummers method followed by grinding, which was taken as 9:1 ratio (nHAp/ZnO and GO) of weight, enhances its tensile and mechanical strength. The energy band gap of nHAp photocatalyst was evaluated as 3.39 eV and that of the in nHAp/ZnO/GO photocatalyst was narrowed to 1.77 eV. The ternary nanocomposites are very efficient in generating the photogenerated electrons and holes, thereby improving the degradation potential of dye effluents to by-products such as CO2 and H2O. The nanocomposites photocatalyst were characterized by FTIR, XRD, SEM, TEM, EDS, XPS, DRS, and BET techniques. The UV-visible study shows the complete dye degradation efficiency of the prepared nanocomposites photocatalyst. In this study, the prepared nanocomposites nHAp/ZnO/GO have studied their efficiency for the removal of MB dye in a batch process by varying the dosage from 0.1 to 0.5 g, and the effects of dosage variations, pH, kinetic, scavenger study were evaluated at a time interval of 30 min. The removal of dye was found to be 99% at 150 min of 0.3 g dosage and pH = 12 is most favorable as it reached the same percentage at 90 min. The as-prepared nanocomposite nHAp/ZnO/GO fits the kinetic rate constant equation and shows a pseudo-first-order reaction model. This study indicates the suitability for dye removal due to the synergistic effect and electrostatic interaction of the synthesized ternary nanocomposite, which shows the potential, socially active, low-cost-effective, eco-friendly, and safe for photocatalytic degradation of MB from wastewater.

Deciphering the mechanistic role of Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52) in bio-sorption and phyto-assimilation of Cadmium via Linum usitatissimum L. Seedlings

Three Cd2+ resistant bacterium's minimal inhibition concentrations were assessed and their percentages of Cd2+ accumulation were determined by measurements using an atomic absorption spectrophotometer (AAS). The results revealed that two isolates Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52), identified by 16S rDNA gene sequencing, showed a higher percentage of Cd2+ accumulation i.e., 83.78% and 81.79%, respectively. Moreover, both novel strains can tolerate Cd2+ levels up to 2000 mg/L isolated from district Chakwal. Amplification of the czcD, nifH, and acdS genes was also performed. Batch bio-sorption studies revealed that at pH 7.0, 1 g/L of biomass, and an initial 150 mg/L Cd2+ concentration were the ideal bio-sorption conditions for Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52). The experimental data were fit to Langmuir isotherm measurements and Freundlich isotherm model R2 values of 0.999 for each of these strains. Bio sorption processes showed pseudo-second-order kinetics. The intra-diffusion model showed Xi values for Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52) of 2.26 and 2.23, respectively. Different surface ligands, was investigated through Fourier-transformation infrared spectroscopy (FTIR). The scanning electron microscope SEM images revealed that after Cd2+ adsorption, the cells of both strains became thick, adherent, and deformed. Additionally, both enhanced Linum usitatissimum plant seed germination under varied concentrations of Cd2+ (0 mg/L, 250 mg/L,350 mg/L, and 500 mg/L). Current findings suggest that the selected strains can be used as a sustainable part of bioremediation techniques.

Polypyrrole-decorated bentonite magnetic nanocomposite: A green approach for adsorption of anionic methyl orange and cationic crystal violet dyes from contaminated water

In the presented study, a novel polypyrrole-decorated bentonite magnetic nanocomposite (MBnPPy) was synthesized for efficient removal of both anionic methyl orange (MO) and cationic crystal violet (CV) dyes from contaminated water. The synthesis of this novel adsorbent involved a two-step process: the magnetization of bentonite followed by its modification through in-situ chemical polymerization. The adsorbent was characterized by SEM/EDX, TEM/SAED, BET, TGA/DTA-DTG, FTIR, VSM, and XRD studies. The investigation of the adsorption properties of MBnPPy was focused on optimizing various parameters, such as dye concentration, medium pH, dosage, contact time, and temperature. The optimal conditions were established as follows: dye concentration of Co (CV/MO) at 100 mg/L, MBnPPy dosage at 2.0 g/L, equilibrium time set at 105 min for MO and 120 min for CV, medium pH adjusted to 5.0 for MO dye and 8.0 for CV dye, and a constant temperature of 303.15 K. The different kinetic and isotherm models were applied to fit the experimental results, and it was observed that the Pseudo-2nd-order kinetics and Langmuir adsorption isotherm were the best-fitted models. The maximal monolayer adsorption capacities of the adsorbent were found to be 78.74 mg/g and 98.04 mg/g (at 303.15 K) for CV and MO, respectively. The adsorption process for both dyes was exothermic and spontaneous. Furthermore, a reasonably good regeneration ability of MBnPPy (>83.45%/82.65% for CV/MO) was noted for up to 5 adsorption-desorption cycles with little degradation. The advantages of facile synthesis, cost-effectiveness, non-toxicity, strong adsorption capabilities for both anionic and cationic dyes, and easy separability with an external magnetic field make MBnPPy novel.

ZnO@ activated carbon derived from wood sawdust as adsorbent for removal of methyl red and methyl orange from aqueous solutions

Activated carbon (AC) and ZnO@AC composite derived from wood sawdust were prepared to be utilized as adsorbents for methyl red (MR) and methyl orange (MO) anionic dyes from the aqueous solutions. The maximum adsorption capacity of the AC and ZnO@AC composite toward both dyes was achieved in the strong acidic medium (pH = 3), and under stirring for 60 min. The kinetic studies revealed that the adsorption of MR and MO dyes onto the AC and ZnO@AC composite fitted well with the pseudo-second-order model. Furthermore, the intraparticle diffusion and Elovich kinetic models confirmed the adsorption is controlled by external surfaces, and the adsorption is chemisorption process. The isotherm results indicated that the MR and MO dye adsorption occurred via monolayer adsorption, and the estimated maximum adsorption capacities of both dyes onto the ZnO@AC composite were higher than those achieved by AC. Thermodynamic analysis suggested that the adsorption is endothermic and spontaneous. The mechanism for MR, and MO dyes adsorption onto the AC and ZnO@AC composite is proposed to be controlled by electrostatic bonding, π-π interactions, and ion exchange, while H-bonding and n-π interactions were minor contributors. This study reveals the potential use of carbon-based adsorbents derived from wood sawdust for the removal of anionic dyes from wastewater.

Chemical modification of Aloe vera leaf hydrogel for efficient cadmium-removal from spiked high-hardness groundwater

Herein, the hydrogel from the leaf of the Aloe vera plant (ALH) was succinylated (SALH) and saponified (NaSALH). The FTIR, solid-state CP/MAS 13C NMR, and SEM-EDX spectroscopic analyses witnessed the formation of SALH and NaSALH from ALH. The pHZPC for NaSALH was found to be 4.90, indicating the presence of -ve charge on its surface. The Cd2+ sorption efficiency of NaSALH was found to be dependent on pH, NaALH dose, Cd2+ concentration, contact time, and temperature. The maximum Cd2+ removal from DW and HGW was found to be 227.27 and 212.77 mg g-1 according to the Langmuir isothermal model (>0.99) at pH of 6, NaSALH dose of 40 mg g-1, Cd2+ concentration of 90 mg L-1, contact time of 30 min, and temperature of 298 K. The kinetic analysis of Cd2+ sorption data witnessed that the Cd2+ removal by chemisorption mechanism and followed pseudo-second-order kinetics (>0.99). The -ve values of ΔG° and ΔH° assessed the spontaneous and exothermic nature of sorption of Cd2+ by NaSALH. The regeneration and sorption/desorption studies indicated that the sorbent NaSALH is regenerable.

A novel ZIF-8@IL-MXene/poly (N-isopropylacrylamide) nanocomposite hydrogel toward multifunctional adsorption

Phenols, dyes, and metal ions present in industrial wastewater can adversely affect the environment and leach biological carcinogens. Given that the current research focuses only on the removal of one or two of those categories. Herein, this work reports a novel ZIF-8@IL-MXene/Poly(N-isopropylacrylamide) (NIPAM) nanocomposite hydrogel that can efficiently and conveniently absorb and separate multiple pollutants from industrial wastewater. Ionic liquid (IL) was grafted onto MXene surfaces using a one-step method, and then incorporated into NIPAM monomer solutions to obtain the IL-MXene/PNIPAM composite hydrogel via in-situ polymerization. ZIF-8@IL-MXene/PNIPAM nanocomposite hydrogels were obtained by in-situ growth of ZIF-8 on the pore walls of composite hydrogels. As-prepared nanocomposite hydrogel showed excellent mechanical properties and can withstand ten repeated compressions without any damage, the specific surface area increased by 100 times, and the maximum adsorption capacities for p-nitrophenol (4-NP), crystal violet (CV), and copper ion (Cu2+) were 198.40, 325.03, and 285.65 mg g-1, respectively, at room temperature. The VPTTs of all hydrogels ranged from 33 to 35 °C, so the desorption process can be achieved in deionized water at 35-40 °C, and its adsorption capacities after five adsorption-desorption cycles decreased to 79%, 91%, and 29% for 4-NP, CV, and Cu2+, respectively. The adsorption data fitting results follow pseudo-second-order kinetics and Freundlich models, which is based on multiple interactions between the functional groups contained in hydrogels and adsorbent molecules. The hydrogel is the first to realize the high-efficiency adsorption of phenols, dyes and metal ions in industrial wastewater simultaneously, and the preparation process of hydrogels is environmentally friendly. Also, giving hydrogel multifunctional adsorption is beneficial to promote the development of multifunctional adsorption materials.

Synergistic effect of adsorption and photo-catalysis on the removal of hazardous dyes using steam exploded banana fiber derived micro-cellulose

The utilization of banana fiber derived from micro-cellulose (MC) was exploited as a supporting material for advanced oxidation process (AOP) on the degradation of methylene blue and methyl violet dyes in the presence of H2O2-UV in aqueous medium for the first time using green chemistry protocols. Additionally, it was also effectively utilized for the adsorption of methylene blue dye using addition of H2O2 in the presence of sunlight. The MC powder was fabricated using an acid alkali process from the pseudo-stem of a banana tree. The as-fabricated MC powder was systematically characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectrometer (EDX), and zero point charge (pHzpc). The AOP assisted degradation of dye molecules was monitored by using calorimetric techniques as a function of dye concentration and pH in a batch reactor. In a short period of time, the maximum degradation efficiency of 98 % of methylene blue was achieved using MC powder assisted H2O2 under UV irradiation at a minimum irradiation time of 120 min at pH 7.0 using dosage of 0.2 g/L. However, in the absence of UV light, the degradation efficiency of MC powder assisted H2O2 was only about 5-10 % without UV light irradiation. The dye removal was studied as a function of various operational parameters such as pH (3-11), catalyst dose (0.2-0.6 g/L), and initial dye concentration (100-400 mg/L). In the presence of H2O2-sunlight and 0.2 g/L of dosage at pH 7.0 at a minimum contact time of 120 min, MC fiber showed maximum adsorption capacities of 98% and 85% for 100 mg/L and 400 mg/L of methylene blue concentrations. According to the obtained data, the adsorption of methylene blue dye on MC follows the Freundlich isotherm model (R2 = 0.9886) and pseudo-first-order kinetic model (R2 = 0.9596) due to the higher regression coefficients. This process of dye degradation and adsorption process is a novel one and environmentally benign for an effective removal of hazardous dyes.

Clay-moringa seedcake composite for removal of cationic and anionic dyes

The present study investigated the potential of a composite prepared from kaolinite clay and moringa seedcake in removing methylene blue (MB) and acid orange-7 (AO-7) dyes from aqueous solutions using batch and column tests. The composite was modified using different chemicals during the synthesis process, and the composites were characterised using different techniques such as FTIR, SEM-EDS and XRD. Characterisation showed the presence of actively charged functional groups and porous structure on the composites prepared. Batch tests were performed to assess the effect of operating conditions such as adsorbent dosage, pH, initial dye concentration and contact time. NaOH-modified and H2SO4/NaOH-modified composites demonstrated the highest adsorption capacities for AO-7 and MB, respectively, and were selected for subsequent studies. The adsorption process of dye was best fitted by the Freundlich isotherm and pseudo-second-order kinetic models suggesting that the sorption of MB and AO-7 onto the composites is a heterogeneous, multilayer chemical adsorption process. Long-term fixed-column tests were conducted with the composites to assess the impact of flow rate, bed depth and initial dye concentration on the dye removal efficiency. Optimum removals of 86 and 94%, respectively at pH 2 and pH 10 were obtained for AO-7 and MB in batch tests, along with adsorption capacities of 205.65 and 230.49 mg/g for AO-7 and MB. Results from the column tests were best explained by the Clark model and the Bed Depth-Service Time model. Competing ions impacted the removal of AO-7, while no significant effect was found for MB. The composites could be reused up to four cycles without significantly affecting the adsorption capacity. The present study thus shows the potential of the composite for removal of both the dyes.

Bio-based nanocomposite hydrogels derived from poly (glycerol tartrate) and cellulose: Thermally stable and green adsorbents for efficient adsorption of heavy metals

The eco-friendly polymeric nanocomposite hydrogels were prepared by incorporating dendritic fibrous nanosilica (DFNS) and apple peel (AP) as reinforcements into the crosslinked polymer produced by cellulose (CL) and poly (glycerol tartrate) (TAGL) via gelation method and used for efficient adsorption of Pb2+, Co2+, Ni2+, and Cu2+ metal ions. DFNS and DFNS/TAGL-CL/AP samples were characterized by FESEM, FTIR, TEM, TGA, and nitrogen adsorption/desorption methods. The results of TGA analysis showed that the thermal stability of the prepared hydrogels improved significantly in the presence of DFNS. Both synthetic and environmental parameters were investigated and the adsorption capacity reached 560.2 (pH = 4) and 473.12 (pH = 5) mg/g for Pb2+ and Cu2+ respectively, using initial ion concentration of 200 mg/L. Also, the maximum adsorption capacity was 340.9, and 350.3 mg/g for Co2+ and Ni2+, respectively under optimum conditions (pH = 6, initial ion concentration of 100 mg/L). These experiments indicated that the DFNS/TAGL-CL/AP nanocomposite hydrogel has an excellent performance in removal of Pb2+ and can adsorb this toxic metal in only 30 min while the optimum contact time for other metals was 60 min. Pseudo-second-order and Langmuir models were used to define the kinetic and adsorption isotherms, respectively and thermodynamic studies demonstrated that the adsorption was endothermic for Co2+, Ni2+ and Cu2+, exothermic for Pb2+, and spontaneous in nature for all metal ions. Furthermore, the reusability tests indicated that the hydrogels could maintain up to 93% of their initial adsorption capacity for all metal ions after four cycles. Therefore, the prepared nanocomposite hydrogels can be suggested as efficient adsorbents to remove the toxic metals from wastewater.

Efficacious adsorption of divalent nickel ions over sodium alginate-g-poly(acrylamide)/hydrolyzed Luffa cylindrica-CoFe2O4 bionanocomposite hydrogel

Existing Ni2+ heavy metal ions in an aqueous medium are highly hazardous for living organisms and humans. Therefore, designing low-cost adsorbents with enhanced effectiveness is essential for removing nickel ions to safeguard public health. In this study, a novel green nanocomposite hydrogel was synthesized through the free radical solution and bulk polymerization method, and its capability to remove divalent nickel ions from aqueous media was examined. The bionanocomposite hydrogel named as SA-g-poly(AAm)/HL-CoFe2O4 was produced by grafting polyacrylamide (AAm) onto sodium alginate (SA) in the presence of a magnetic composite recognized as HL-CoFe2O4, where HL represents hydrolyzed Luffa Cylindrica. By employing FT-IR, XRD, VSM, SEM, EDX-Map, BET, DLS, HPLC, and TGA techniques, morphological evaluation and characterization of the adsorbents were carried out. The performance of the adsorption process was studied under varying operational conditions including pH, temperature, contact duration, initial concentration of pollutant ions, and adsorbent dosage. HPLC analysis proved the non-toxic structure of the bionanocomposite hydrogel. The number of unreacted acrylamide monomers within the hydrogel matrix was measured at 20.82 mg/kg. The optimum conditions was discovered to be pH = 6, room temperature, adsorbent dosage of 1 of g.L-1, initial Ni2+ concentration of 10 mg.L-1, and contact time of 100 min, and the maximum adsorption efficiency at optimal state was calculated as 70.09, 90.25, and 93.83 % for SA-g-poly (AAm), SA-g-poly(AAm)/HL, and SA-g-poly(AAm)/HL-CoFe2O4 samples, respectively. Langmuir isotherm model was in good agreement with the experimental data and the maximum adsorption capacity of SA-g-poly(AAm), SA-g-poly(AAm)/HL, and SA-g-poly(AAm)/HL-CoFe2O4 samples was calculated to be 31.37, 43.15, and 45.19 mg.g-1, respectively. The adsorption process, according to kinetic studies, follows a pseudo-second-order kinetic model. Investigations on thermodynamics also demonstrated that the process is exothermic and spontaneous. Exploring the interference effect of co-existing ions showed that the adsorption efficiency has decreased with concentration enhancement of Ca2+ and Na+ cations in aqueous medium. Furthermore, the adsorption/desorption assessments revealed that after 8 consecutive cycles, there had been no noticeable decline in the adsorption effectiveness. Finally, actual wastewater treatment outcomes demonstrated that the bionanocomposite hydrogel successfully removes heavy metal pollutants from shipbuilding industry effluent. Therefore, the findings revealed that the newly fabricated bionanocomposite hydrogel is an efficient, cost-effective, easy-separable, and green adsorbent that could be potentially utilized to remove divalent nickel ions from wastewater.

A novel magnetic Fe3O4/cellulose nanofiber/polyethyleneimine/thiol-modified montmorillonite aerogel for efficient removal of heavy metal ions: Adsorption behavior and mechanism study

To efficiently remove heavy metals from wastewater, designing an adsorbent with high adsorption capacity and ease of recovery is necessary. This paper presents a novel magnetic hybridized aerogel, Fe3O4/cellulose nanofiber/polyethyleneimine/thiol-modified montmorillonite (Fe3O4/CNF/PEI/SHMMT), and explores its adsorption performance and mechanism for Pb2+, Cu2+, and Cd2+ in aqueous solutions. The hybrid aerogel has a slit-like porous structure and numerous exposed active sites, which facilitates the uptake of metal ions by adsorption. Pb2+, Cu2+, and Cd2+ adsorption by the hybridized aerogel followed the second-order kinetics and the Langmuir isotherm model, the maximum adsorption of Pb2+, Cu2+, and Cd2+ at 25 °C, pH = 6, 800 mg/L was 429.18, 381.68 and 299.40 mg/g, respectively. The adsorption process was primarily attributed to monolayer chemical adsorption, a spontaneous heat-absorption reaction. FTIR, XPS and DFT studies confirmed that the adsorption mechanisms of Fe3O4/CNF/PEI/SHMMT on Pb2+, Cu2+, and Cd2+ were mainly chelation, coordination, and ion exchange. The lowest adsorption energy of Pb2+ on the hybrid aerogel was calculated to be -2.37 Ha by DFT, which indicates that the sample has higher adsorption affinity and preferential selectivity for Pb2+. After 5 cycles, the adsorption efficiency of the aerogel was still >85 %. The incorporation of Fe3O4 improved the mechanical properties of the aerogel. The Fe3O4/CNF/PEI/SHMMT has fast magnetic responsiveness, and it is easy to be separated and recovered after adsorption, which is a promising potential for the treatment of heavy metal ions.

Green preparation of magnetic ferroferric oxide-polyvinyl alcohol-alginate coated UiO-67 nanospheres: Characterization, adsorption properties and adsorption mechanism of methylene blue

In this paper, a kind of magnetic ferric oxide/polyvinyl alcohol/calcium alginate/UiO-67 (Fe3O4/PVA/CA/UiO-67) nanospheres with homogeneous surface interconnecting structures was prepared by using macromolecular polymer polyvinyl alcohol and sodium alginate as carriers and zirconium organic skeleton as nanocrystals. The properties of magnetic nanospheres were studied by SEM, FT-IR, TGA, XRD, BET, VSM and Zeta potential. The impression of diverse temperatures, MB concentrations, interaction time, pH, and magnetic aerogel sphere dose on MB removal was studied. The optimum adsorption temperature and pH of magnetic nanospheres for MB were 298 K, and 10, respectively. Langmuir simulated that the maximum removal of MB by magnetic nanospheres at room temperature (298 K) was 1371.8 mg/g. The removal of MB by magnetic nanospheres complied with the pseudo-first-order kinetic model. The isotherm simulation can infer that the Langmuir model was more comply with MB adsorption on magnetic aerogel spheres. Thermodynamic studies have confirmed that the removal of MB by magnetic nanospheres was exothermic and spontaneous. The interaction mechanism of MB on magnetic nanospheres can be deduced by FT-IR and BET, including hydrogen bond, π-π bond, electrostatic interaction, and mesoporous pore flow. The removal rate of nanospheres for MB still reached 70.06 % after six cycles.

Cost-effective removal of toxic methylene blue dye from textile effluents by new integrated crosslinked chitosan/aspartic acid hydrogels

Chitosan/aspartic acid hydrogels were synthesized for MB dye removal from textile aqueous effluents with different ratios by gelation of chitosan with non-toxic gelling agent, crosslinker, glutaraldehyde (Glu). The obtained hydrogels were characterized by spectral and morphological techniques. The characterization techniques confirmed successful preparations and MB dye adsorption. Batch experiments were done to investigate the effects of adsorbent dose, pH, contact time, temperature, and initial MB dye concentration. The optimum conditions were: adsorbent dose 0.1 g, pH 5, contact time 30 min, and temperature 25 °C for Chitosan-Aspartic Acid Hydrogel 1 (CSAA-HG1) and adsorbent dose 0.4 g, pH 2, contact time 60 min, temperature 25 °C for Chitosan-Aspartic Acid Hydrogel 2 (CSAA-HG2). Adsorption capacity of newly hydrogels CSAA-HG1,2 was compared with each other. Adsorption efficiencies reached 99.85 % for CSAA-HG1 and 99.88 % for CSAA-HG2. MB dye adsorption on CSAA-HG1,2 followed Freundlich isotherm model (R2 = 0.94 and 0.92, respectively). Both adsorbents exhibited pseudo-second-order kinetics for MB dye adsorption (R2 = 1). The negative ΔHo indicated that the MB dye adsorption was exothermic, negative ΔGo confirmed that MB dye adsorption process was spontaneous and low values of ∆So indicated low degree of freedom, ordered MB dye molecules on CSAA-HG1,2 surfaces.

Bamboo cellulose-derived activated carbon aerogel with controllable mesoporous structure as an effective adsorbent for tetracycline hydrochloride

Activated carbon has been widespread applied in the removal of pollutants in wastewater. However, many biomass-derived activated carbon suffer from the challenge of controllable pore size regulation, hindering their efficient adsorption of pollutants. Herein, bamboo-derived activated carbon aerogel (BACA) has been successfully prepared through KOH high-temperature activation of cellulose aerogel which was prepared using cellulose extracted from bamboo. Bamboo cellulose aerogel provides sufficient reaction sites for KOH, which is conducive to the formation of a mass of mesoporous structures on the pore walls of the activated carbon aerogel. The optimal BACA adsorbent shows high specific surface area (2503.80 m²/g), and maximum adsorption capability for tetracycline hydrochloride (TCH) reaches 863.8 mg/g at 30 ℃. The removal efficiencies of TCH are 100% and 98.4% at 40 ℃ when the initial concentrations are 500 and 700 mg/L, respectively. Adsorption kinetics and isotherm indicate that the adsorption of BACA for TCH is monolayer adsorption based on chemical adsorption. Spontaneous and endothermic adsorption processes are proved by adsorption thermodynamic studies. Additionally, coexisting ions have insignificant effect on TCH adsorption, and the BACA sample displays excellent adsorption property for five reuse cycles with a removal efficiency of 80.95%, indicating the outstanding adsorption capacity of BACA in practical application. The excellent adsorption performance provides BACA with a promising perspective to remove TCH from wastewater, and the prepared method of BACA can be widely extended to other biomass materials.

Graphene oxide supported sulfidated nano zero-valent iron (S-nZVI@GO) for antimony removal: The role of active oxygen species and reaction mechanism

Sulfidated nano zero-valent iron (S-nZVI) was used to remove various pollutants from wastewater. However, the instability, poor dispersibility, and low electron transfer efficiency of S-nZVI limit its application. Herein, graphene oxide supported sulfidated nano zero-valent iron (S-nZVI@GO) was successfully synthesized using graphene oxide (GO) as a carrier. The properties of S-nZVI@GO were characterized by scanning electron microscopy coupled to X-ray photoelectron spectroscopy (SEM-EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) concerning the surface morphology, crystalline structure, and elemental components. S-nZVI@GO displayed an excellent capacity for antimony (Sb) removal under aerobic conditions (96.7%), with a high adsorption capacity (Q_max = 311.75 mg/g). It maintained a high removal rate (over 90%) during a wide pH range (3-9). More importantly, S-nZVI@GO activated the molecular oxygen in water via a single-electron pathway to produce •O₂－ and H₂O₂, and then oxidized trivalent antimony (Sb(III)) to pentavalent antimony (Sb(V)) and further separated it by synergistic adsorption and co-precipitation. Therefore, S-nZVI@GO shows excellent potential for Sb contamination remediation.

Fabrication and characterization of magnetic nanomaterials for the removal of toxic pollutants from water environment: A review

The success of any sustainable growth represents an advancement of novel approaches and new methodologies for managing any ecological concern. Magnetic nanoparticles have gained recent interest owing to their versatile properties such as controlled size, shape, quantum and surface effect, etc, and outcome in wastewater treatment and pollutant removal. Developments have progressed in synthesizing magnetic nanoparticles with the required size, shape and morphology, surface and chemical composition. Magnetic nanoparticles are target specific and inexpensive compared to conventional treatment techniques. This review insight into the synthesis of magnetic nanoparticles using physical, chemical, and biological methods. The biological method of synthesizing magnetic nanoparticles serves to be cost-effective, green process, and eco-friendly for various applications. Characterization studies of synthesized nanoparticles using TEM, XRD, SARS, SANS, DLS, etc are discussed in detail. Magnetic nanoparticles are widely utilized in recent research for removing organic and inorganic contaminants. It was found that the magnetic nanosorption approach together with redox reactions proves to be an effective and flexible mechanism for the removal of pollutants from waste effluents.