Preparation and Application of Cow Dung Biochar Adsorbent in Removal of Pesticide Residues and Polycyclic Aromatic Hydrocarbons (PAHs) From Water

Abstract

This study aimed at preparing and assessing the potential of cow dung biochar (CDB) in adsorption of selected pesticides (tebuconazole, λ-cyhalothrin and α-cypermethrin) and polycyclic aromatic hydrocarbons (PAHs) (naphthalene, phenanthrene and anthracene) from water. CDB was prepared by low temperature pyrolysis (300–350 ℃) and characterized for surface morphology, composition, crystallinity, phases and thermal properties before assessing its adsorption efficacy at different conditions, isotherm models and regeneration capacity for the target pesticides and PAHs. The morphologies of the samples indicated an amorphous structurewith –OH groups. The composite char had four phases of amorphous, transition, compos- ite and turbostratic char phase while depicting high thermally stability. The adsorption capacities ranged between 78 and 91%. The optimal adsorption conditions were 20 ℃ at a pH range of 4.0–8.0 for 30 min. Temkins adsorption was the most favored model. Chemisorption was exhibited for all sorbates except λ-cyhalothrin while following both pseudo-first order and Akrami-Erovich models. The adsorption processes were spontaneous under room temperature conditions. The adsorbents had an adsorption capacity of 63–80% for the third adsorption cycle indicating they would be regenerated successfully. As a matter of fact, the prepared CBD showed potential for removal of the chemical pollutants’ removal. Keywords Pesticides · PAHs · Cow dung biochar · Adsorption.