Oxidation of Cylindrospermopsin by Fenton Process: A Bench-Scale Study of the Effects of Dose and Ratio of H2O2 and Fe(II) and Kinetics

Abstract

The cyanotoxin cylindrospermopsin (CYN) has become a significant environmental and human health concern due to its high toxicological potential and widespread distribution. High concentrations of cyanotoxins may be produced during cyanobacterial blooms. Special attention is required when these blooms occur in sources of water intended for human consumption since extracellular cyanotoxins are not effectively removed by conventional water treatments, leading to the need for advanced water treatment technologies such as the Fenton process to produce safe water. Thus, the present study aimed to investigate the application of the Fenton process for the degradation of CYN at bench-scale. The oxidation of CYN was evaluated by Fenton reaction at H2O2/Fe(II) molar ratio in a range of 0.4 to 4.0, with the highest degradation of about 81% at molar ratio of 0.4. Doubling the concentrations of reactants for the optimized H2O2/Fe(II) molar ratio, the CYN degradation efficiency reached 91%. Under the conditions studied, CYN degradation by the Fenton process followed a pseudo-first-order kinetic model with an apparent constant rate ranging from 0.813 × 10−3 to 1.879 × 10−3 s−1.

Evaluation of the Removal and Effects of Cylindrospermopsin on Ripened Slow Sand Filters

“…TOC was measured on a Shimadzu 500 carbon analyzer. CYN was measured by LC-MS/MS using the same equipment and following the same procedure described by Ferreira et al [ 27 ].…”

“…Given the risk posed by the presence of CYN in water supply sources, the use of appropriate treatment techniques for its removal is essential. Several water treatment techniques are available, including chemical oxidation [ 27 ] and adsorption onto activated carbon [ 28 , 29 ]. In the context of appropriate technologies for decentralized water treatment, slow sand filtration effectively removes cyanotoxins from water [ 30 , 31 ], which is particularly important in areas with frequent cyanobacterial blooms.…”

Removal of Cyanobacteria and Cyanotoxins in Waters

“…Three other papers address different advanced oxidation processes used to remove cyanotoxins [7][8][9]. Advanced oxidation processes involve a set of oxidative water treatments, including treatment with UV-O 3 , UV-H 2 O 2 , the Fenton process, the photo-Fenton process, and nonthermal plasmas as well as sonolysis, photocatalysis, and radiolysis, all based on the production of powerful, highly reactive oxidants.…”

“…Among those oxidants, hydroxyl radicals are the most commonly used and are the strongest known oxidants after fluorine, and, similar to other highly reactive oxidants, can nonselectively destroy the majority of organic matter and can mineralize organic pollutants in water. Against that background, Ferreira et al [7] investigated the applicability of the Fenton process to mineralize cylindrosmpermopsin by analyzing how the dosage of Fenton reagents, namely H 2 O 2 and Fe(II), and the H 2 O 2 -to-Fe(II) molar ratio affected the removal of cylindrosmpermopsin in ultrapure water (i.e., unrealistic conditions that do not consider water matrix effects or real pH) [7]. Although the Fenton process is a promising advanced oxidation technique that can be easily implemented at full scale worldwide due to its simplicity and highly cost-effective technology, the water matrix effect and large-scale volumes need to be investigated to evaluate the process for application in treating cyanotoxins because the presence of scavengers and competing species identified in real water matrices may affect degradation kinetics.…”