Sustainable Water Treatment: Use of Agricultural and Industrial Wastes to Remove Mercury by Biosorption

Mercury is a potential contaminant of the aqueous systems that needs to be removed from wastewaters even in trace concentrations due to its hazardous effects on environment and human health. Agricultural and industrial wastes are produced in abundance in many agro-industrial activities and have no commercial costs associated with them. The Hg(II) ions can establish bonds with the functional groups present on lignocellulosic biomasses, making the use of these types of biosorbents excellent alternatives to remove mercury in water treatments, while promotes their recycling and valuation. In this work, six biosorbents (banana and potato peels, eggshells, Eucalyptus globulus bark, water hyacinth, and coffee waste) were tested and compared under the same batch conditions with an initial mercury concentration of 50 mu g dm(-3) in order to determine their removal performances. Several reaction- and diffusion-based models were adjusted to the experimental data to analyze the limiting sorption mechanisms. Sorption experiments and modelling results evidenced distinct affinities of those biosorbents to Hg(II), banana peels being the best alternative due to the fast removal kinetics and capacity. This biosorbent was able to remove more than 90 % of the Hg(II) initially in solution after 72 h of exposure, being more than 80 % removed in the first 10 h. Chemical and physical characteristics of the solids are involved in Hg(II) elimination, as reported by FTIR-ATR and SEM studies.