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The presence of dyes in waterbodies poses severe problems in human and aquatic creatures, and the development of treatment methods for the removal of these pollutants is of utmost importance. This research study investigates the elimination of methylene blue (MB) from an aqueous solution using zero-valent iron nanoparticles synthesized from sweet lime pulp waste (nZVISLP). The purity, chemical composition, and crystalline size of nZVISLP were investigated using microscopic and spectroscopic studies. A maximum MB removal efficiency of 98.9% was obtained at the following optimal conditions: C0: 10 mg/L, dosage: 1.2 g/L, and temperature: 25 °C. To understand the adsorptive removal characteristics of nZVISLP, the investigational adsorption data were tested with conventional kinetic and isotherm models. Furthermore, a differential evolution optimization (DEO) technique was used to estimate the optimal intrinsic parameters in the isotherm and kinetic models. For the various evaluated isotherms, the correlation coefficient (R2) values for the Freundlich and Sips isotherm models were ~0.98, thus confirming the aptness of these isotherms to represent MB adsorption onto nZVISLP. The robustness of non-linear models was verified by statistical metrics, thus validating the performance of the optimization technique. The results derived from this study affirm the potential of an ecofriendly biogenic nanomaterial, nZVISLP, for MB adsorptive removal.

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The present study investigated the adsorption efficiency of magnetic activated carbon was synthesized by waste biomass of Pisum sativum (peel) and pyrolysis at 500˚C temperature (MPPAC-500). Derived activated carbon was applied for removal of fluoride from aqueous solution. The MPPAC-500 was characterized by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), zeta potential, X-ray Diffraction (XRD) and Particle Size Analyser. The fluoride sequestration study was performed in both batch and column systems. The batch adsorption study was focused on parameter like, adsorbent dose, contact time, pH and initial fluoride concentrations. The maximum capacity of fluoride removal was qo = 4.71 (mg/g). Freundlich isotherm model (R2 -0.995) obeyed better than Langmuir (R² -0.979) model. The RL values observed between 0-1 (RL-0.057) inferred the favourable adsorption. Pseudo-second-order model favoured well than pseudo-first-order in the whole experimental data. In case of column study was performed at two different bed height 5 cm and 10 cm having flow rate of 5 mL/min as well as 10 mL/min. The breakthrough curve and column data were interpreted by Thomas, Adams-Bohart, Yoon-Nelson and Clark model. These finding showed that MPPAC-500 has potential adsorptive capacity for fluoride removal from aqueous solutions in batch and column systems.

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