Visible light driven metals (Gd and Tl) doped TiO₂ nanoparticles (NPs) were prepared using low cost and facile liquid impregnation method. The prepared NPs were characterized using XRD, SEM/EDX, BET surface area analysis, particle size distribution analyzer, UV–Vis DRS and pH of point of zero charge (pH_PZC) analyses. The crystalline phases observed were purely anatase with the particles size ranged between 24 and 30 nm possessing large surface area (74 m²/g) and pore size (12 nm). The reductions in the band gap energy for both the dopant systems were observed and absorption edges were extended to the visible region. The prepared NPs exhibited good photo-induced adsorption affinity for the As(III) from aqueous solution under natural pH of As(III) solution, ambient temperature and normal household compact fluorescent light. The metals-doped NPs showed high removal efficiency (up to 99%) towards As(III) compared to pure TiO₂ NPs (68%). In addition, the glass beads immobilized photocatalyst not only enhanced the efficiencies by increasing the active surface area of NPs, but also overcome the post-reaction separation steps. The regeneration study indicated that the physical regeneration is more significant for the reutilization of photocatalysts.

Agricultural waste based low cost oxidized activated carbon (OSD) and un-oxidized activated carbon (USD) samples were prepared from saw dust of Ziziphus jujube by chemical activation with phosphoric acid (H₃PO₄). The activated carbon was used for the removal of toxic metal ions such as cadmium(II) and lead(II) from aqueous solutions. The effect of pH (2–9), initial concentration (70–100 mg/L), contact time (5–700 min), activated carbon dose (0.1–1.0 g) and temperature (298–328 K) was investigated. In addition, the kinetic study was performed at pH 6, while the carbon dose of 0.1 g was used for 40 mL solution of 70 mg/L at four different temperatures (298, 308, 318 and 328 K). The adsorption efficiency of USD was found higher than OSD. Comparatively higher uptake of Pb(II) ions was observed by each carbon sample. Pseudo-second order equation best fitted the experimental data. As such, both activated carbon samples (USD and OSD) exhibited higher adsorption capacities and faster kinetics which revealed their commercial usefulness.