abstract
Mercury and cadmium are considered by the water framework directive priority hazardous substances. In this work, the capacity of crab carapace and clam shell wastes to remove mercury and cadmium from water was evaluated under batch conditions, for realistic contamination scenarios in monometallic and binary solutions. The results evidenced that in monometallic solutions and under studied operational conditions, both biosorbents can achieve Hg2+ removal efficiencies higher than 80% and the kinetic process is well described by two of the most widely used equations, the pseudo-second order and the Elovich model. In terms of biosorption equilibrium, crab carapace and clam shell wastes displayed very distinct behaviours. While clam shells achieve the complete monolayer coverage and the isotherm is well described by the Langmuir model, crab carapace powder display a more unusual behaviour, that is well described by the BET isotherm, and is characterized by an almost convex shape to the concentration axis, with an infinite slope for an Hg2+ concentration in solution around 25 mu g/L. In binary solutions, both wastes are able to uptake simultaneously Hg2+ and Cd2+, however the uptake of Hg2+ was inhibited in some extent, attributed to the high kinetic and equilibrium selectivities of the bio-wastes for cadmium. (C) 2016 Elsevier Ltd. All rights reserved.
keywords
CRAB SHELL PARTICLES; AQUEOUS-SOLUTIONS; METAL-IONS; BIOSORPTION; MERCURY; EQUILIBRIUM; EFFLUENTS; ZINC(II); SOLIDS; GASES
subject category
Engineering
authors
Monteiro, RJR; Lopes, CB; Rocha, LS; Coelho, JP; Duarte, AC; Pereira, E
our authors
Cláudia Batista Lopes
Assistant Researcheracknowledgements
We would like to thank University of Aveiro, FCT/MEC for the financial support to CESAM, CICECO and CIIMAR (UID/AMB/50017/2013; UID/CTM/50011/2013; UID/Multi/04423/2013) through national funds and, where applicable, co-financed by the FEDER, within the PT2020 Partnership Agreement.; We also would like to thank the National Funds through the Portuguese Foundation for Science and Technology (FCT) through a FCT project (PTDC/MAR-BIO/3533/2012), postdoctoral grants to C. B. Lopes and J.P. Coelho (SFRH/BPD/99453/2014; SFRH/BPD/102870/2014), and a doctoral grant to R.J. Monteiro (SFRH/BD/108535/2015). L.S. Rocha also thanks FCT project FCTANR/AAG-MAA/0065/2012 for her grant.