Studies of selective adsorption, desorption and reuse of chemically altered biomass produced from aquatic macrophytes for treatment of metal-containing wastewater

Abstract

The aquatic macrophytes Salvinia sp. and Pistia stratiotes have a natural capacity to adsorb various elements, including heavy metals. This capacity was enhanced with a chemical treatment using NaOH alkaline solution for Salvinia sp. and a mixture of both Salvinia sp. and Pistia stratiotes at a proportion of 1:1, whose respective biosorbents were called SSOH and MBOH. Adsorption tests were done in a ternary system containing the metals copper, lead and manganese; the parameters considered were: starting concentration, kinetics, pH and temperature. The adsorption isotherms for SSOH had a maximum adsorptive capacity of 50.20, 53.85 and 14.68 mg g-1 for Cu, Pb and Mn, respectively; for MBOH, maximum values were 44.62, 35.17 and 15.74 mg g-1 for Cu, Pb and Mn, respectively. The metals displayed different behaviors with pH variation. The results also showed an adsorption preference of Cu> Pb>Mn for SSOH. Desorption and readsorption studies were also carried out, showing 100% desorption and increased adsorption capacity in readsorption tests. Surface area and porosity analysis with the Brunauer-Emmett-Teller (BET) method indicate that after chemical modification, MBOH and SSOH biomasses had their surface increased in comparison to SS, with values of 165.5657 (MBOH), 157.4392 (SSOH) and 78.9432 m2 g-1 (SS).