Removal of Lead from Aqueous Solution on Activated Carbon and Modified Activated Carbon Prepared from Dried Water Hyacinth Plant

Abstract

In this work, the potential of activated carbon stems and leaves (ACS, ACL) prepared from dried water hyacinth stems and leaves (DS, DL) by chemical activation with phosphoric acid (1:3) and modified activated carbon stems and leaves (MACS, MACL) with nitric acid (1:1) for the removal of lead from aqueous solution was investigated. Carbon samples were produced with a reasonable yield about 75% and have a remarkable surface area (57.46, 71.83, 864.52, 493.78, 381.22, and 265.22 m2/g for DS, DL, ACS, and ACL, MACS and MACL, respectively and well developed pore structure. Batch adsorption experiments were conducted to study the effect of various operating parameters, pH of the solution (1 to 6), initial concentration of lead ions (50 to 400 mg /l), contact time (2-250 min), and temperature (298-323 K). It is obvious that the maximum adsorption of lead at pH 5 is in the order: MACS (175.63 mg/g) > MACL (164.56 mg/g) > DS (90.50 mg/g) > DL (66.60 mg/g) > ACS (36.00 mg/g) > ACL (33.40 mg/g). This may be attributed to the increase in the number of active sites on the modified activated carbon. The equilibrium data were analyzed using Langmuir and Freundlich isotherms. The results showed that the experimental data were fitted well by the Langmuir model. Kinetic results revealed that the adsorption process obeyed a pseudo-second order model and intra-particle diffusion was the rate controlling step. The thermodynamic studies revealed that the adsorption was spontaneous and endothermic process. Desorption of about 90% of the sorbed lead from carbon was achieved using about 0.6 M HCl.