A DFT study of the adsorption of fouling molecules (metal sulfides and hydroxides) onto TiZrO4 ceramic membranes

Abstract

Ceramic membrane fouling is a constraint in the treatment of acid mine drainage (AMD), leading to a decrease in efficiency over time. Here, it is described via first-principles calculations the physical and chemical phenomena occurring on the surface of TiZrO4 filtration membranes due to the adsorption of eight potential fouling compounds [CuS, FeS, Fe2S3, CaS, Al(OH)3, Fe(OH)3, Fe(OH)2, and Cu(OH)2]. The interaction of these fouling molecules was performed onto nanostructured TiZrO4 surfaces with several pores representing the filtration membranes employed in the treatment of AMD. The adsorption energies reveal that the adsorption is feasible with all the fouling molecules studied, and it is strongly related to the molecular polarity of the adsorbate. Consequently, the adsorption of metal sulfides is more feasible than hydroxides with adsorption orders of CaS>FeS>CuS>Fe2S3, and Al(OH)3>Fe-hydroxides>Cu(OH)2. The outcomes suggest that the metal sulfide adsorption depends on the adsorbate intrinsic polarity, solvent effects, adsorbate van der Waals radius, and membrane surface topology, while the adsorption of hydroxides is less influenced by the last two factors. Density-based binding and energy decomposition analyses indicate strong electrostatic attractions and covalent bonds at the adsorbate-membrane interface supporting the chemical fouling onto ceramic filtration membranes. According to our theoretical results and the elevated concentration of Cu and Fe in AMD, we propose that FeS and CuS are mainly responsible for the fouling onto TiZrO4 membrane surfaces. These results offer valuable information on the adsorption phenomena at TiZrO4 membrane surfaces, which can be useful for metallurgy, industrial water treatment, food industry, biotechnology, and pharmaceutical applications.