Improving the effectiveness of safe cyanotoxin removal from drinking water using magnetic iron oxide nanoparticle-loaded carbon composites

Abstract

Climate change and eutrophication have increased cyanobacterial blooms, raising exposure to cyanotoxins in drinking water. This study investigates efficacy improvement of two magnetic nanostructured particles with different adsorbent materials, mesoporous carbon (P-Mes) and Merck activated carbon (P-MAC), for cyanotoxin removal. Safety of these materials is also investigated in extreme conditions of physical deterioration. Their efficacy was tested using pre-cleaning with organic solvents, different toxin concentrations, particle/volume ratios and toxin mixtures. Acetonitrile and ethanol pre-cleaning improved toxin adsorption in both particles. P-Mes particles demonstrated high adsorption for high-molecular-weight toxins, achieving 97 % removal of microcystin-LR at a particle-to-water ratio of 1:750 μL, and were also effective removing seven other microcystins and saxitoxin. P-MAC particles exhibited superior performance for low-molecular-weight toxins, achieving removal rates of 98 %, 91 % and 83 % for anatoxin-a, saxitoxin, and cylindrospermopsin respectively, at a particle-to-water ratio of 1:1.5 mL. Additionally, combination of particles or toxin mixtures did not inhibit their effectiveness. In vitro toxicity assessments using pulverized particles to increase possible release of toxic components indicated no cytotoxicity in SH-SY5Y, CACO-2, HepG2, and CAKI-1 lines, and no alteration of CACO-2 monolayers electrical resistance. Overall, materials preconditioning, particle-to-volume ratio adjustment, and selection of appropriate composite combination enhances removal of nine toxins.