Valorization of Opuntia ficus-Indica Pads and Steel Industry FeCl3-Rich Rejection for Removing Surfactant and Phenol from Oil Refinery Wastewater Through Coagulation-Flocculation

Abstract

Background. Refinement of crude vegetable oil generates a large amount of wastewater and is a source of water pollution due to the presence of surfactants and phenols. Phenols are toxic aromatic compounds that can be lethal to fauna and flora, entraining the deceleration or blocking of the self-purification of biological treatments. In addition, surfactants can limit biological processes by inhibiting microorganisms that degrade organic matter. Objectives. The aim of the present study was to evaluate the treatment of refinery rejects loaded with phenols and detergents by coagulation flocculation using cactus pads (genus Opuntia) as a bio-flocculant and 30% iron(III) chloride (FeCl3) for surfactant and phenol removal. In addition, operating costs were evaluated for these pollution mitigation methods. Methods. The effectiveness of cactus pads as a bio-flocculant and 30% FeCl3 for surfactant and phenol removal were studied using a jar test. The study was conducted on vegetable oil refinery wastewater from a refinery company in Casablanca, Morocco. Results. The pollution load in wastewater varied widely from day to day. We evaluated the effect of cactus juice and 30% FeCl3 on high and low pollution loads. Opuntia pads showed a favorable potential for the treatment of low pollution load wastewater, with 78% and 90% of surfactant and phenol removed, respectively. However, the removal of high pollution load was less effective (42% and 41% removal of surfactant and phenol, respectively). The turbidity of low and high pollution load was reduced by 98.85% and 86%, respectively. The results demonstrate that 30% FeCl3 can effectively treat both low and high pollution loads (90% and 89% phenol removal, respectively, and 90% and 70% surfactant removal, respectively (optimal concentration 1.48 g/l). The turbidity was reduced by over 96% for both high and low pollutants. Conclusions. The results of the present study indicate that cactus as a natural flocculant and reject rich in FeCl3 could be effectively used for the low-cost effective treatment of crude vegetable oil refinery rejects. Competing Interests. The authors declare no competing financial interests