Adsorptive removal of lead(II) from an aqueous solution by chemically modified cottonseed cake

The present study explores the ability of activated carbon prepared from sulphuric acid-treated cottonseed cake (SCSC) by chemical activation with sulphuric acid for the removal of Pb(II) from an aqueous solution. Batch experiments were carried out by varying several conditions such as contact time, solution pH, adsorbent dose and temperature along with commercial activated carbon (CAC). According to the experimental results, the equilibrium time and optimal pH range were found to be 3 h and 4.0–6.0, respectively. The equilibrium data were analysed based on the Freundlich, Langmuir, Redlich–Peterson and Dubinin–Radushkevich isotherms using nonlinear regression analysis and fit well with the Langmuir model. Based on the Langmuir isotherm, the adsorption capacity was found to be 115.86 mg/g for SCSC, which was substantially (5.3 times) greater than that of CAC (21.69 mg/g) at 300 K. The thermodynamic investigations indicated that the adsorption reactions were spontaneous and exothermic in nature. The results of the kinetic study showed that the adsorption of Pb(II) could be described by the pseudo-second-order equation, suggesting that the adsorption process is presumably chemisorptions with film diffusion. A single-stage batch adsorber was designed for different adsorbent dose using the Langmuir equation.