The sorption of highly toxic Cr(VI) ions by cassava waste biomass was quantitatively investigated. The sorption was found to be influenced by several physico-chemical factors such as agitation speed, temperature, contact time, pH, and sorbent/sorbate ratio. The adsorption data at equilibrium were fitted to Freundlich and Langmuir isotherms. The monolayer sorption capacity was found to be 61.79 mg of Cr(VI) per gram of biomass. The kinetics of Cr(VI) adsorption to pure cassava-tuber-bark wastes were determined based on a pseudo-second-order-rate model using the batch-sorption technique at a temperature of 30 degrees. The kinetics data suggest that the adsorption process is exothermic, and that the rate-limiting step is physisorption. Negative DeltaG(ads) values indicate that the adsorption is spontaneous and exothermic in nature. Also, under optimal conditions (in agitated 1M H(2)SO(4) at 30 degrees), the cassava waste biomass appears to be recyclable.
The processing waste of the aerial roots of Rhizophora mangle was used in both its unmodified or mercaptoacetic acid (MAA) modified form for the sorption of Pb2+ from aqueous solution. The biomass rapidly and strongly sorbed Pb2+ at pH 5.0, which indicated chemisorption. A significant increase in Pb2+ sorption resulted from MAA treatment of the biomass, indicating that sorption occurs through an ion-exchange process. From sorption-capacity experiments, the unmodified and modified materials extracted, at pH 5, 31.3 and 85.5 mg of Pb2+ per gram of biomass, respectively, from aqueous solutions. Our studies may contribute to an innovative method for the economical and ecologically save removal and recovery of heavy-atom metal ions from contaminated waters through biosorption.
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