Equilibrium Studies and Optimization of Phosphate Adsorption from Synthetic Effluent Using Acid Modified Bio-Sorbent

Abstract

Adsorption potential of periwinkle shell (PRW), an agricultural waste, for the removal of phosphate from aqueous solution was investigated through equilibrium studies at various experimental conditions. PRW was carbonized and chemically activated with 1MH₂SO₄ before it was subjected to characterization using Fourier Transform Infrared (FT-IR), Energy Dispersive X-ray (EDX) and Scanning Electron Microscopy (SEM). Adsorption data were analyzed using various kinetic and isotherm models. Statistical modeling through Central Composite Design (CCD) was also employed. The results showed that, FT-IR spectrum of the activated PRW shows many absorption peaks and a variety of functional groups such as –OH, -NH, C = O, C-H, C-N, CH₃ and CH₂ which explains its improved adsorption behavior on the colloidal particles. SEM shows the morphological changes with respect to the shape and sizes of the adsorption sites.EDX indicates the higher percentage composition of carbon (11.66%), Oxygen (63.18%) as important constituent elements for adsorption. Equilibrium data were well fitted to pseudo second order kinetic model and were best described by Langmuir Isotherm model at the temperature of 303K. Removal efficiency of 95.90% was obtained. A statistical model equation was developed for the adsorption process which reveals contact time as the most significant main effect for performance of the adsorbent.