Equilibrium and Kinetic Studies on Sorption of Boron on Industrial Wastes

Abstract

Boron in the forms of boric acid or borate salts are found widely in the environment, either in natural or anthropogenic sources. A variety of technologies can be used to remove boron from drinking water, but not all of them are cost-effective. An analysis and comparison were made of two different industrial solid wastes—red mud (RM) and fly ash (FA)—that are used to remove boron from the aqueous solution. Sorption equilibrium and kinetic studies were carried out using batch mode. The effect of pH (2–11), sorbent dosage (4–75 g/L), shaking period (10–210 min), shaking speed (80–180 rpm), and sorbate concentration (10–200 mg/L) on the sorption for both the sorbents were studied in experiments conducted in batch mode. At a pH value of 8 for RM and 10 for FA, a sorbate dose of 30 g/L and shaking speed of 150 min, the percentage boron removal was maximum for both the sorbents. Out of various sorption isotherm models, the Langmuir isotherm appeared to be the best fit (R2 > 0.99). It was found that the sorption kinetics were in agreement with the pseudo second-order model for boron on RM and FA, as it gave the highest R2 value as compared with the pseudo first-order and intraparticle diffusion models. According to the findings, these industrial wastes could be used to remove boron at a much lower cost than commercial sorbents.