A novel adsorbent poly (methyl methacrylate)-grafted alginate/Fe₃O₄ nanocomposite was synthesized by oxidative-free radical-graft copolymerization reaction. The nanocomposite was characterized using FT-IR, X-ray diffraction, SEM, TEM, TGA and DSC techniques. The potential of nanocomposite material was explored towards the adsorption of Pb(II) and Cu II) from aqueous media under varying operating conditions such as pH, concentration of metal ions, contact time, adsorbent dose and temperature. The optimum pH recorded for metal ions adsorption was 5. The experimental data were tested using Langmuir, Freundlich, Sips and Temkin models, and the data were best followed by Freundlich model at 50°C. The maximum sorption capacity was found to be 62.5 mg g⁻¹ for Pb(II) and 35.71 mg g⁻¹ for Cu(II), respectively. The concentration and temperature dependent rate constants were evaluated using various kinetic models, and the data were best followed by pseudo-second-order kinetic model. The thermodynamic parameters such as enthalpy, entropy and free energy of activation were calculated to explain the nature of adsorption process.

In this study, L-cystein-modified montmorillonite (MMT)-immobilized sodium alginate biopolymer-based nanocomposite was synthesized using solution casting method. The synthesized material was characterized by X-ray diffraction, FTIR, TGA-DTG, scanning electron microscopy and transmission electron microscopy techniques. The material was further evaluated for the removal of heavy metal ions like (Pb²⁺, Ni²⁺ and Cu²⁺) from aqueous solutions. The effect of various parameters such as pH, agitation time, initial metal ion concentration, temperature and adsorbent dose on the extent of adsorption was investigated. The equilibrium data obtained by experiments were well analysed by four isotherm models, and the results are well fitted with Langmuir model at 50°C, and a maximum adsorption capacity (q_m) 100.00, 111.11 and 125.00 (mg g⁻¹) was obtained for Cu²⁺, Pb²⁺ and Ni²⁺, respectively. Various kinetic equations were applied to kinetic data, and the results are best found to follow pseudo-second-order kinetic model. Thermodynamic parameters of the adsorption process such as the standard Gibbs free energy change (∆G°), standard enthalpy change (∆H°), standard entropy change (∆S°) were calculated, and the result showed that adsorption of heavy metals onto Alg-Cys-MMT is spontaneous and endothermic in nature.

The green mechanism for the synthesis of nanoparticles and their application to the wastewater treatment is of inordinate curiosity to the research community. Herein we outline a novel method for the synthesis of silver nanoparticles via a green route using alginate-guar gum blend (GG-Alg@Ag) and their application to degrade methylene blue (MB) dye. The synthesized material was characterized by FTIR, XRD, SEM-EDX, TEM, TGA-DTG, AFM, and UV-vis techniques. A combination of RSM and CCD was employed to compute the system and optimized values of various interacting parameters such as exposure time (120 min), pH (4.98), dye concentration (194 mg L⁻¹), and catalyst dose (0.07 g) with a photodegradation capacity of 92.33% and desirability 1.0. The mechanism of degradation reaction was best elucidated by the pseudo-second-order model suggesting chemical deposition of MB on the GG-Alg@Ag surface through followed by the reduction mechanism in the occupancy of visible light. The optical studies indicated a value of 2.5 eV by Tauc's plot for bandgap energy (E_g) for GG-Alg@Ag bionanocomposite.

In the present study, ecofriendly green synthesized ZnO/CuO nanorods were prepared by using the stabilizing and reducing characteristics of the alginate biopolymer. The bionanocomposite (BNC) material was characterized by various sophisticated analytical tools such as Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy–energy dispersive X-ray spectroscopy, transmission electron microscopy, UV–visible spectroscopy, differential scanning calorimetry, and the Brunauer–Emmett–Teller (BET) method. The composition of ZnO/[email protected] BNC was found to be C (16.16 ± 0.42%), O (42.26 ± 1.87%), Cu (31.96 ± 1.05%), and Zn (9.62 ± 0.48%), which also supports the approximate 3:1 ratio of Cu²⁺ and Zn²⁺ taken as the precursor. The nanocrystalline spinel ferrite was found to have a BET specific surface area of 19.24 m² g^–1 with a total pore volume of 0.075 cm³ g^–1 and 1.45 eV as the band gap energy (E_g). Further, the material was applied for the photodegradation of p-nitrophenol (PNP) under the advanced oxidative process (AOP) under visible sunlight irradiation. The visible light radiation was used for the degradation of PNP under pH 2 conditions and resulted in 98.38% of the photocatalytic efficiency of the ZnO/[email protected] catalyst within 137 min of irradiation time. The photocatalytic reaction was best defined by the pseudo-first-order kinetics which involves the adsorption of the PNP molecule on the surface of the catalyst, thereby demineralizing it in the presence of advanced active ^•OH radicals. The values of rate constant for the pseudo-first-order model (k₁) were calculated as 0.013, 0.016, 0.019, 0.021, and 0.023 min^–1 with half-life periods of 53.31, 43.31, 36.47, 33.00, and 30.13 min for 10–50 mg L^–1 PNP concentrations. The presence of t-butyl alcohol decreases the photocatalytic efficiency, which suggests that the degradation of PNP was accomplished by the ^•OH oxidative radical.

Statistics show that more than 700 thousand tons of dye are produced annually across the globe. Around 10–20% of this is used in industrial processes such as printing and dyeing, while about 50% of the dye produced is discharged into the environment without proper physicochemical treatment. Even trace amounts of dye in water can reduce oxygen solubility and have carcinogenic, mutagenic, and toxic effects on aquatic organisms. Therefore, before dye-containing wastewater is discharged into the environment, it must be properly treated. The present study investigates the green synthesis of nickel ferrite NiFe₂O₄ (NIFE) spinel magnetic nanoparticles (MNPs) via chemical coprecipitation of a solution of Ni²⁺/Fe³⁺ in the presence of a biopolymer blend of chitosan (CT) and ascorbic acid (AS). The magnetic nanomaterial was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy–energy dispersive X-ray analysis (SEM-EDX), transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), differential scanning calorimetry (DSC), and vibrating-sample magnetometry (VSM). The material was further explored as a catalyst for the photocatalytic degradation of malachite green (MG) under visible light irradiation coupled with ultrasonic waves. The combination of 90 min of visible solar light irradiation with 6.35 W·mL⁻¹ ultrasonic power at pH 8 resulted in 99% of the photocatalytic efficiency of chitosan-ascorbic acid@NIFE (CTAS@NIFE) catalyst for 70 mg·L⁻¹ MG. The quenching of the photocatalytic efficiency from 98% to 64% in the presence of isopropyl alcohol (IPA) suggested the involvement of hydroxy (^•OH) radicals in the mineralization process of MG. The high regression coefficients (R²) of 0.99 for 35, 55, and 70 mg·L⁻¹ MG indicated the sonophotocatalysis of MG by CTAS@NIFE was best defined by a pseudo first-order kinetic model. The mechanism involves the adsorption of MG on the catalyst surface in the first step and thereby mineralization of the MG by the generated hydroxyl radicals (^•OH) under the influence of visible radiation coupled with 6.34 W·mL⁻¹ ultrasonic power. In the present study the application of photodegradation process with sonochemistry results in 99% of MG mineralization without effecting the material structure unlike happens in the case adsorption process. So, the secondary pollution (generally happens in case of adsorption) can be avoided by reusing the spent material for another application instead of disposing it. Thus, the ecofriendly synthesis protocol, ease in design of experimentation like use of solar irradiation instead of electric power lamps, reusability and high efficiency of the material suggested the study to be potentially economical for industrial development at pilot scale towards wastewater remediation.