Adsorptive removal of phosphate using nano cobalt hydroxide as a sorbent from aqueous solution; multivariate optimization and adsorption characterization

Abstract

A unique application of Cobalt hydroxide nanoparticles is proposed in the current study. Particles were synthesized and used for removal of phosphate in a batch system. Here, the main variables e.g. pH, sorbent dosage (m), and initial concentration of phosphate (CP) were considered with an assumption that they were likely to be influential on both removal efficiency (R %) and capacity uptake (q). Response surface methodology (RSM) involving Box-Behnken design (BBD) was employed to optimize effective factors and subsequently to propose an appropriate regression model of adsorption system. Apart from that, the kinetic and thermodynamic studies of phosphate adsorption onto the nano-adsorbent were carried out. Second-order kinetic model shows more favorability for dynamic behavior of current adsorption process. The thermodynamic parameters such as ΔG, ΔH and ΔS were determined and results testified that the adsorption procedure is spontaneous and endothermic in its nature. FT-IR, energy dispersive X-ray microanalysis (EDX) for elemental analysis/composition, powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) were applied to characterize bare and adsorbed materials. FT-IR analysis imparted a confirmation that the surface of sorbent is involved in the adsorption process. Desirable potential of nano-sized cobalt hydroxide was reported for removal of phosphate from aqueous medium as an entire result.