Kinetics and Thermodynamic Study of Balsalazide Adsorption by Unsaturated Polyester Resin (UPR): A Non-carbon Adsorbent

The presence of human pharmaceutical compounds in surface waters is an emerging issue in environmental science. While water purification techniques such as granular activated carbon could potentially remove these pollutants from wastewater streams, the high cost involved suggests that more attention should be given to the potential for the optimization of current treatment processes and reduction at source in order to reduce environmental contamination. Unsaturated Polyester Resin (UPR) was used in the adsorptive removal of Balsalazide, anti-inflammatory drug, from an aqueous solution. It was found that UPR with a higher specific surface area adsorbed and removed more Balsalazide from an aqueous solution. Factorial design of experiments is employed to study the effect of four factors pH (7-12), temperature (30, 40 and 50 degrees C), adsorbent dosage (30 mg L-1) and initial concentration of the BSZ (1.0x 10(-4) mol dm(-3)). The kinetic adsorption studies demonstrate adsorption is usually complete within 10-15 min. The estimated values for Delta G(o) were -5.98x10(3) over UPR at 303 K (30 degrees C), which indicate toward a spontaneous nature of the process, and the positive heats of enthalpy suggest the endothermic nature of the process. Adsorption kinetics and isotherms were determined from the experimental data, and the results revealed that the adsorption followed pseudo-first-order kinetics with good correlation coefficients. In addition, it was found that the adsorption of Balsalazide occurred in two consecutive steps, including the slow intra-particle diffusion of Balsalazide molecules through the UPR.