A cost–effective and eco-friendly treatment technology to remove realistic levels of mercury by means of the unmodified rice husk

Department of Chemistry/CESAM, University of Aveiro, 3810-193 Aveiro, Portugal

^a lrocha@ua.pt
^b claudia.b.lopes@ua.pt
^c aduarte@ua.pt
^d eduper@ua.pt

Abstract

In the present work the removal of mercury from aqueous solutions media and for realistic concentrations of this metal was evaluated, by using an inexpensive and highly available agricultural waste, rice husk. An economical method was developed based on the use of the natural/unmodified form of rice husk and on the amount of material required, which was minimized to produce the lowest amount of biological slurry. In order to study the kinetics of the process, batch stirred experiments were performed for initial concentrations of Hg²⁺ of: 50 μg L^–1, representing the actual maximum value for Hg discharges from industrial sectors, and 500 μg L^–1, to simulate a situation of an accidental spill. The kinetic curves were described by a rapid removal of Hg²⁺ by rice husk, in the first hours of contact, followed by a slower removal of Hg²⁺, until it reaches equilibrium. The removal of Hg²⁺ using a rice husk dose of 0.50 g L^–1 was ca. 83% for an initial concentration of 50 μg L^–1 and 92% for 500 μg L^–1. Furthermore, the results show that is possible the reuse the rice husk in additional cleaning treatments, maintaining the efficiency of the removal process.