Effects of different activation methods on the capacity of an agro-waste adsorbent in the removal of organochlorine pesticides and heavy metals contaminants from wastewater

Abstract

In the present study, the effects of different activation methods on the capacity of an agro-waste adsorbent in the removal
of multi-component contaminants from wastewater were investigated. The adsorbents were treated using sodium
hydroxide (NaOH), dichloromethane (DCM), distilled water, sulphuric acid (H2SO4), n-hexane, and nitric acid (HNO3),
and the eluted effluents were analyzed for the levels of organochlorine pesticides and heavy metals using Gas
Chromatography-Mass Spectrometer (GC-MS) and Atomic Absorption Spectrometer (AAS), respectively. The percentage
recoveries of the organochlorine pesticides (87 - 98%) indicated that the precision, reliability, and reproducibility of the
adopted procedure were acceptable. The results of the study showed that DCM-treated adsorbents exhibited the highest
removal efficiency for the organochlorine pesticides with 100%, 99.64%, and 91.89% of chlorinated benzenes,
dichlorodiphenylethanes, and cyclodienes respectively, being removed while distilled water-treated adsorbents exhibited
the lowest removal efficiency. In contrast, the H2SO4-, HNO3-, and NaOH-treated adsorbents exhibited significant
removal (>80%) of Cd, Cu, and Pb from the wastewater. The removal of pesticide congeners by organic solvents was
ascribed to the theory that similarities are easily solvable in each other while the removal of metal ions by inorganic acids
was attributed to the creation of more acidic functional groups on the adsorbent’s surface. The economic feasibility and
eco-friendliness of the process pave way for further research and development into the optimization of reaction conditions
for the complete removal of these contaminants.