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Herein, the green synthesis of TiO2 nanoparticles using Phyllanthus niruri leaf extract was accomplished by the sol‐gel method. The structure and particle size of the synthesised TiO2 nanoparticles were characterised by X‐ray diffraction (XRD) analysis and the size was found to be 20 nm. The Fourier‐transform infrared spectra determined the existence of carboxyl and hydroxyl functional groups. The images from SEM analysis recommended a porous and heterogeneous surface. The methyl orange (MO) dye removal was examined using different parameters such as pH, time, dose, temperature and dye concentration. Maximum dye elimination percentage was achieved at pH 6.0 and 0.02 g as the optimum adsorbent dose. The kinetic analysis suggested that the pseudo‐second‐order kinetic model finely defines adsorption dynamics. Langmuir adsorption isotherm studies revealed endothermic monolayer adsorption of the methyl Orange dye. The negative value of ∆G° and positive value of ∆H° showed the spontaneous and endothermic adsorption method. [ABSTRACT FROM AUTHOR]

Activated carbon was prepared from Citrus limettioides seed (CLSC), a novel waste material by chemical modification with sulfuric acid was applied for the adsorption Ni(II) from aqueous solutions. The effect of contact time, pH, adsorbent dose, initial metal ion concentration, and temperature were studied in batch experiments. According to the experimental results, the equilibrium time, optimum pH range, and adsorbent dosage were found to be 3 h, pH = 4.0-8.0 and 1 g L−1, respectively. In addition, raw Citrus limettioides seeds (CLS) were used as adsorbents at the same parameters. Ni(II) removal for CLSC and CLS were obtained 99.00% and 37.00% in turn. The equilibrium data agreed well with Langmuir model, which confirmed the monolayer coverage of Ni(II) ions onto CLS and CLSC. The Langmuir monolayer adsorption capacity of the CLSC was found to be 36.06 mg g−1 which was significantly about 3.5 times greater than that of CLS (10.23 mg g−1) at 300 K. The kinetic data followed pseudo-second order model and intra-particle diffusion was not the sole rate-controlling factor. Surface morphology and structural analysis of CLSC prior to and after adsorption were characterized by SEM and EDX. The presence of hydroxyl, carboxylic, and sulfonic acid groups are confirmed by FTIR spectra. The adsorbents were also tested for the removal of Ni(II) from electroplating wastewater in connection with the reuse and selectivity of the adsorbents. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1384-1395, 2015 [ABSTRACT FROM AUTHOR]