Removal of Pb from Aqueous Solution Using Sepiolite Clay, Corn Biochar, and Clay-biochar Complex

Increasing population and water consumption in agriculture and industry sectors enhanced the entry of various pollutants into the environment and water resources. In this study, the removal of lead from water by three adsorbents, sepiolite clay, corn biochar, and corn biochar-clay complex were investigated. For this purpose, the adsorption isotherms and kinetics were performed by the three studied adsorbents. By increasing the concentration in lead from 50 to 1500 mg L-1, the absorption capacity of the adsorbents increased, but the absorption percentage decreased. The results showed that the lead highest absorption capacity is related to the corn biochar adsorbent, while the clay-biochar complex had a higher absorption capacity than the clay adsorbent. To study the absorption process, Langmuir and Freundlich's isotherms were checked for each adsorbent and it was found that the absorption of lead follows both models, but the Langmuir model with the highest coefficient of explanation (R2) and the lowest sum of squared standard error (SSE) has the best fit. The effect of contact time with the adsorbent on the absorption rate was investigated and it was found that the absorption efficiency increased with increasing contact time. The pseudo-first-order, pseudo-second-order, Elovich and intraparticle diffusion kinetic models were fitted for lead at concentrations of 600, 1000 and 1500 mg L-1 in 30 to 1440 min. The Elovich model at the concentration of 500 mg/L and the pseudo-second order model at the concentrations of 1000 and 1500 mg/L showed the best fit with the laboratory data. At low concentrations, the clay-biochar complex showed better absorption performance, but biochar was a better absorber with increasing lead concentration than the other two adsorbents.