(217dv) Selective Adsorption and Removal of Heavy Metals From Seawater By Nanosorbents

Sim, V., The Hong Kong University of Science and Technology
Chen, X., The Hong Kong University of Science and Technology
Ng, T. N., The Hong Kong University of Science and Technology
Yeung, K. L., The Hong Kong University of Science and Technology

Heavy metal pollution in seawater is an increasing concern due to the rapid growth in seawaters use from industrial oil extraction to district cooling installation and in production of potable waters to supplement the diminishing supply of fresh waters. Heavy metal can persist and accumulate with long-term and wide-ranging impact on marine ecosystem. It is therefore important to develop technology that can effectively remedy metal pollution in seawater. The sorption process remains the most economical means of removing heavy metals, but the high salt and organic content of seawater pose important challenges. This work investigates the design and preparation of functionalized nanosorbents for selective adsorption and removal of Cu2+, Zn2+, Ni2+, Co2+, Cd2+, As(V), Sb(III), Cr(VI) from seawater. 

Mono-/di- /tri- amino-organoalkoxysilanes were grafted on the walls of MCM-41 to capturing heavy metal cations (e.g. Cu2+, Zn2+, Ni2+, Co2+, Cd2+) and Fe3+ sorption to the amino groups to create adsorbents for removing heavy metal anions (e.g. As(V), Sb(III), Cr(VI)). The experimental results showed NH2-MCM-41 can selectively remove more than 99% copper with a Kd of 106 from seawater at pH 8, while the NNN-MCM-41 has good affinity for adsorption of cadmium from seawater. The Fe-NNN-MCM-41 nanosorbent on the other hand removes Cr(VI) from seawater (pH8) with a removal percentage of >99% and Kd of 106. Batch and fixed-bed column adsorption studies were carried out to obtain the adsorption kinetics and isotherm for potential practical application.