Critical review on lanthanum-based materials used for water purification through adsorption of inorganic contaminants
Kok Yuen Koh, Yi Yang, J. Paul Chen
Abstract
Water pollution is a serious global environmental problem as many pollutants are highly carcinogenic to humans (e.g., arsenic) and cause disruption in the ecosystem (e.g., phosphorus for eutrophication). Therefore, development and application of cost-effective technologies are of great importance to meet the increasing stringent regulations and the greater challenges in the water contamination. This article provides a comprehensive review of publications in lanthanum (La)-based adsorbents that are exceptionally effective for the removal of several common inorganic contaminants from aqueous solutions. The abilities of lanthanum compounds (e.g., La2(CO3)3) as standalone adsorbents or La-incorporated adsorbents (e.g., with activated carbons) were summarized and discussed in detail. The reported studies have demonstrated that the lanthanum compounds particularly work well in the adsorption of inorganic anions (e.g., arsenic and fluoride). In addition, the incorporation of lanthanum onto some supporting materials would result in better adsorption with a lower material cost, due to better dispersion of lanthanum and well distributed active functional groups. The mechanisms of adsorption mainly include ligand exchange, surface complexation and electrostatic attraction. Various evidences given in the literatures demonstrate that, the La-based adsorbents are commercially viable and well outperform the commercial materials (e.g., ion exchange resins, activated carbons and iron oxides) for the water and wastewater treatment, in particular for the removal of anionic pollutants.