Metals, particularly heavy metals (HM), are the leading source of marine pollution. They enter the marine environment by a variety of natural and anthropogenic processes, including rock weathering, volcanic eruptions, air deposition, domestic sewage, industrial effluents, agricultural discharge, mining, coastal construction activities, dredging, and so on. Aerogels, xerogels, and cryogels are sol-gel produced mesoporous materials with several exceptional features such as low density, high porosity, and variable surface chemistry that are of particular relevance in environmental remediation applications. This chapter provides an overview of the synthesis and applications of these materials in environmental applications.

Because of their huge specific surface area and high porosity, activated carbons are currently a viable adsorbent substrate for the removal of organic and inorganic chemicals from solutions. The chemical characterization of activated carbon, as well as the environmental load associated with its manufacture, is a critical point that challenges researchers all over the world to develop feasible absorbents at cheap cost and with minimal environmental impact. Thallium levels have been reported to rise dramatically in both water and aquatic biota after exposure to metal mine effluent, but little is known about its fate and impact in the aquatic environment.