Removal of Various Pollutants from Aquatic Environments with Cashew Processing Waste (a Literature Review)

Abstract

The paper summarizes literature data on the use of Cashew nut shells as a sorption material to remove metal ions (Cd2+, Co2+, Cr(III), Cr(VI), Cu2+, Mn(II), Ni2+, Pb2+, Zn2+), dyes, and phenol from simulated and wastewater. It provides brief information on the amount of Cashew nut shell generated, its chemical composition, and its methods used in various industries as a secondary raw material. The paper presents the Cashew nut shell adsorption process parameters for the pollutants. It is shown that Cashew nut shell treatment with various chemicals improves sorption characteristics for various pollutants. It was found that adsorption isotherms are described by various models, most often by those of Langmuir and Freundlich. In most cases, the process kinetics follows the pseudo-second-order model. It is also shown that Cashew nutshell is a good precursor for activated carbons and carbonizates production, which is also used to remove organic and inorganic pollutants from aquatic environments.