Conventional and Current Methods of Toxic Metals Removal from Water Using g-C3N4-Based Materials

The concentration of toxic metal ions in wastewater continues to increase as a result of the increasing number of industries, and the discharge of their heavy metal-containing wastes directly into water bodies without proper treatment. These heavy metals are highly toxic and difficult to degrade, which makes the treatment and re-use of the wastewater to be very challenging. Several methods have been explored for their removal from water in order to improve on water availability. However, these conventional methods cannot transform the heavy metal ions to a less toxic species, instead they are transferred from one phase to another, which may lead to secondary pollution. In this review, the conventional techniques that have been explored for the removal of heavy metal ions were examined and their merits and demerits were highlighted. Recent advancement involving the use of composites containing graphitic carbon nitride photocatalysts were discussed as viable alternative for the conventional methods. The mechanism of photocatalytic removal of heavy metal ions and methods of synthesizing the g-C 3 N 4 composites were discussed. Furthermore, the chemistry of heavy metal ion transformation, their toxicity and routes of exposure were studied. Finally, the problems associated with the fabrication of the composites were critically examined.