Insights into the efficient elimination of veterinary drug from water by adsorption on activated carbon: optimization study

Abstract

This study aims to investigate the optimal conditions for the elimination of albendazole (veterinary drug) by adsorption on activated carbon, prepared from a plant waste (pericarp of cork oak acorns). This low cost adsorbent was characterized by determining the Brunauer–Emmett–Teller surface area, morphology by using scanning electron microscope and surface chemical properties with Fourier transformed infrared spectroscopy. The pH of solution does not highly affect the adsorption of albendazole, a neutral environment (6.0–7.5) was more favorable. Responses surface methodology, namely Doehlert design was applied to model and optimize the adsorption process. The studied parameters are the pollutant concentration, activated carbon dose and temperature. Two responses were considered, albendazole elimination yield and adsorption capacity. The maximum elimination yield and adsorption capacity were 99.97% and 137.2 mg g−1, respectively. Analysis of variances and Mallows statistic criteria were applied to validate both predictive regression models. Multi-objective methodology using desirability approach was utilized to determine the optimal conditions, which are 50 mg L −1 of pollutant concentration; 1.6 g L −1 of adsorbent dose and 20 °C of temperature, corresponding to elimination yield of 88.8% and adsorption capacity of 82.0 mg g−1. The albendazole adsorption followed pseudo-second order kinetics. All isotherm models applied, namely, Freundlich, Langmuir, Temkin and Dubinin–Radushkevich fitted the experimental data with regression coefficient exceeding 0.930. The albendazole adsorption on the activated carbon was thermodynamically favorable. The application of Boyd’s model showed that the intraparticle diffusion was not the rate limiting step, and the adsorption process may involve several mechanisms.