Cadmium removal from wastewater using carbonaceous adsorbents prepared from sunflower waste

This study reports the removal of cadmium from wastewater in batch mode, using two carbonaceous adsorbents viz. Sunflower Head Carbon (SHC) and Sunflower Stem Carbon (SSC) prepared from waste biomass of sunflower. The adsorbents were characterized by Fourier Transform Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX). The results of batch experiment showed that the cadmium removal was dependent on pH, Cd(II) ion concentration, adsorbent dose, contact time and temperature. The highest cadmium adsorption was found at pH = 6.0, initial Cd(II) concentration = 100 mg/L adsorbent dose = 20 g/L, contact time = 120 min at temperature = 25±1°C and at 180 rpm. Langmuir and Freundlich isotherm models were applied and Freundlich model was found to fit the data well. The Freundlich adsorption capacity was 1.22 and 1.48 mg/g by SHC and SSC. The kinetic data was well described by pseudo-second-order model with coefficient of correlation 0.9978 for SHC and 0.9981 for SSC. The adsorption process was found to be endothermic in nature. The adsorbents were desorbed using different strengths of HCl ranging from 12.5 mM to 200 mM. The highest desorption efficiency i.e. 55.6 and 52.6% from SHC and SSC was found at 125 mM.