Microwave Activated LD Slag for Phenolic Wastewater Treatment: Multi-parameter Optimization, Isotherms, Kinetics and Thermodynamics

LD slag, a by-product of steel making industries, has been modified as low cost adsorbent for removing phenol through adsorption. The modified LD slag has been prepared by acid treatment followed by microwave heating activation. Box Behnken design (BBD) in response surface methodology has been applied to understand the effect of operating variables e.g. acid concentration (0.2-1 N of HCl), microwave radiation time (2-10 min) and power (240-1200 W), in the modification of adsorbent. Optimum conditions of the parameters are obtained with the help of Design Expert 7.0 (Stat-Ease Inc., USA) software. The adsorbent has been characterized by using XRF technique, BET apparatus and SEM images. The BET surface area of the modified LD slag is obtained as 81.18 m2/g. Batch experiments have been conducted at different temperatures (298 K, 308 K, 318 K). Langmuir model fits the experimental data with the maximum adsorption uptake of phenol, onto modified LD slag, as 3.4 mg/g at 298 K. The adsorption kinetics is fitted well to pseudo- second-order model. Thermodynamic analysis proves that the adsorption process is spontaneous in nature and it’s an enthalpy driven process.