Preliminary study on zeolite materials used to control of heavy metal pollution during the culture of mud clam Tegillarca granosa L.

To control heavy metal pollution during the culture of the mud clam, Tegillarca granosa L., the isothermal static adsorption capacities of three adsorption materials [natural zeolites, zeolites synthesized from kaolin and zeolites synthesized from coal fly ash (ZFA)] towards Cu²⁺, Cd²⁺, Cr⁶⁺, Zn²⁺, Pb²⁺ and Hg²⁺ in seawater were investigated. The adsorption capacity of the best material was investigated during the culture of mud clam in an artificially polluted environment. Results showed that the ZFA adsorption capacity was the highest and conformed to the Freundlich model. The theoretical maximum adsorption capacities of the adsorbent towards Cu²⁺, Cd²⁺, Cr⁶⁺, Zn²⁺, Pb²⁺ and Hg²⁺ in seawater were 3.057, 1.123, 0.325, 13.101, 6.116 mg g^?1 and 6.527 μg g^?1 respectively. For seawater artificially polluted by six heavy metals, heavy metal adsorption by ZFA followed the order Zn²⁺ > Cd²⁺ > Hg²⁺ > Cu²⁺ > Pb²⁺ > Cr⁶⁺. For the mud clam culturing experiment that simulated a continuously polluted water source, the Cu²⁺, Cd²⁺, Cr⁶⁺, Zn²⁺, Pb²⁺ and Hg²⁺ contents of mud clam tissues decreased by 40.9%, 25.8%, 9.6%, 28.2%, ?27.8% and 25.7%, respectively, after 21 days of culturing compared with the contents before the experiment.