BioResources (Feb 2017)
Preparation of Activated Carbon from Herbal Residues and Kinetics of Cephalosporin Antibiotic Adsorption in Wastewater
Abstract
In order to utilize the leftover materials from traditional Chinese medicine production and to remove antibiotics from wastewater, extracted herbal residues were used as raw materials to produce activated carbon. To keep a constant quality and adsorption ability across cephalosporin antibiotic samples, all samples were divided into rhizomes, fruits, and leaves to make activated carbon by step-wise carbonization and overheated steam activation. The three kinds of carbon were mixed in the optimal ratio of 5:4:2, which had homogeneity in quality with a high adsorption capacity. Maximum adsorption of the mixture to cefalexin and cefradine were 7.1 mg/g, and the mixture removed 84% of the antibiotics from treated wastewater. Approximately 90% of the antibiotics was desorbed after ultrasonic treatment of the distilled water-carbon mixture for 10 min, and a re-adsorption capacity of 80% was maintained for next use. The adsorption process is dominated by a pseudo-second order kinetic reaction, with two active sites binding to one antibiotic molecule. The rate-limiting step is an intra-particle diffusion process. The isothermal adsorption process conforms to Langmuir and Tempkin isotherm models, showing multilayer and physical adsorption. The activated carbon from herbal residues can adsorb a low concentration of antibiotics in wastewater and be recycled after ultrasonic treatment.
