Systematic studies on the effect of structural modification of orange peel for remediation of phenol contaminated water.

Abstract

In the present study, orange peel biochar has been utilized as the adsorbent for the removal of phenol from contaminated water. The biochar was prepared by thermal activation process at three different temperature 300, 500 and 700°Cand are defined as B300, B500 and B700 respectively. The synthesized biochar has been characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), Fourier Transformation Infrared spectroscopy (FT-IR), RAMAN spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV-Vis Spectroscopy respectively. SEM analysis revealed a highly irregular and porous structure for B700 as compared with others. The parameters such as initial phenol concentration, pH, adsorption dosage, and contact time were optimized, and the maximum adsorption efficiency and capacity of about 99.2% and 31.0 mg/g was achieved for B700 for phenol adsorption. The BET surface area and BJH pore diameter obtained for B700 were about 67.5 m2 /g and 3.8 nm. The adsorption of phenol onto the biochar followed Langmuir isotherm showing linear fit with R2 =0.99, indicating monolayer adsorption. The kinetic data for adsorption is best fitted for pseudo-second-order. The thermodynamic parameters ΔG°, ΔH° and ΔS° values obtained are negative, which means that the adsorption process is spontaneous and exothermic. The adsorption efficiency of phenol marginally declined from 99.2 % to 50.12% after five consecutive reuse cycles. The study shows that the high-temperature activation increased the porosity and number of active sites over the orange peel biochar for efficient adsorption of phenol.