Sorption of lead, cadmium, and zinc on sulfur-containing chemically modified wastes of fluted pumpkin (Telfairia occidentalis HOOK f.)

We have tested the applicability of regular as well as sulfanylacetic acid (SA) modified fluted pumpkin waste biomass as adsorbents for Pb2+, Cd2+, and Zn2+ aqueous solutions by means of the batch-sorption technique. The data revealed that SA modification produces a larger surface area, enhancing the metal-ion binding capacity of the biomass. The sorption process was examined by means of Freundlich and Langmuir models. The kinetic study showed that the sorption rates can be described by a pseudo-second-order process. The rate constants for the control biomass (CB) were 2.2 x 10(-2), 4.4 x 10(-2), and 1.6 x 10(-1) mg g(-1) min(-1) for Pb2+, Cd2+, and Zn2+, respectively; and the corresponding rate constants for the SA-modified biomass were 4.0 x 10(-2), 4.7 x 10(-2), and 1.7 x 10(-1) mg g(-1) min(-1), respectively. Thermodynamic considerations indicated a spontaneous exothermic process, which implies that physisorption is the main mechanism in the sorption process.