Adsorption of the Drug Chlorhexidine Using Organoclay

Organoclays have been used in drug adsorption processes due being cheap and environmentally friendly materials with a good cost benefit for the water treatment industry. The present work evaluated the adsorption of chlorhexidine, an antimicrobial agent, on the organophilic clay Cloisite 30B by using a 23 fractional factorial design. The main and interactive factors studied were the initial chlorhexidine concentration (0.4 and 0.6 mmol/L), adsorbent mass (0.3 and 0.5 g), and contact time (1 and 6 h). The organophilic clay Cloisite 30B was characterized by XRD and FTIR. To evaluate the impact of pH on the adsorption process, a range from 1 to 13 was used, in increments of one pH unit. The chlorhexidine adsorption parameters used the following adsorption conditions: an initial pH of 6, 200 rpm and a reaction temperature of 25 °C. Kinetic data followed the pseudo-second order model, while equilibrium data fit best to the Sips isotherm, suggesting high affinity and capacity. The maximum removal efficiency reached 95.77%, mainly influenced by the initial chlorhexidine concentration. These findings demonstrate the potential of organoclay for removing pharmaceutical contaminants from water pre-treatment of industrial effluents.