Superior adsorptive removal of eco-toxic drug diclofenac sodium by Zn–Al LDH⋅xBi2O3 layer double hydroxide composites

Abstract Recently, efficient removal of eco-toxic pollutant diclophenac sodium (DCF) from wastewater is emerging as crucial problem. However, low adsorption capacity, high cost of conventional adsorbents limits their utility. In this context, Bi2O3 loaded Zn–Al layer double hydroxide (LDH) heterostructures (Zn–Al LDH⋅xBi2O3, x = 0 to 3) have been investigated as a potential adsorbent for DCF removal. These materials are prepared by solvothermal-solvent evaporation method, and systematically characterized by several techniques e.g. XRD, SEM, EDS, HRTEM, XPS, BET and DLS etc. The XRD patterns confirms formation of both LDH and α-Bi2O3 phases. The flower-like morphology is evident by SEM. XPS and EDS confirm Bi2O3-LDH composite. Higher Bi2O3 loading leads to increase in the hydrodynamic sizes of the composite structure. The BET surface area and zeta potential also varies significantly with extent of loading. DCF adsorption of these composites obey the Langmuir adsorption isotherm model suggesting monolayer adsorption process whereas the intra-particle diffusion model indicates that the adsorption of DCF primarily occurs on the exterior surface. The heterostructure with x = 1 exhibited ~10 times higher adsorption capacity compared to bare LDH owing to its highest surface area and positive zeta potential. Due to high adsorption capacities, low cost and easy DCF removal process, these materials could act as efficient adsorbents for removal of DCF and other pollutants from waste water.