Harnessing low-cost adsorbents for removal of heavy metals and metalloids in contaminated water: Progress in the past decade and future perspectives

Heavy metals and metalloids have been a major environmental concern due to their adverse effects on the environmental and human health. Consequently, more cost-effective technologies have been sought for decades to remove the contaminants from contaminated water. As metals and metalloids are nondegradable, adsorption based on low-cost materials has garnered broad interest for its cost-effectiveness, easy operation, and lower environmental impact, especially in developing countries or underserved communities. This review encapsulates the latest progress and the state of the technology on the type, preparation and applications of low-cost adsorbents ranging from natural minerals, biosorbents, materials, agricultural wastes, and modified natural materials to synthetic composite adsorbents. The focus was placed on the technical feasibility, economic effectiveness, pros and cons, as well as influencing factors for treating a range of heavy metals (e.g., lead, zinc, and copper) and metalloids (e.g., arsenic, selenium, tellurium, and antimony) in water. In addition, the underlying adsorption mechanisms were discussed and the technical practicality and economic viability are analyzed by considering the pros and cons as well as relevant environmental factors. Overall, low-cost adsorbents may offer an effective alternative for remediation of water contaminated with metal(loid)s, especially for underdeveloped communities and for non-potable water treatment. Modified or composite adsorbents composed of multiple low-cost materials have shown great promise. This review also identified some critical research needs and knowledge gaps, including eight action items, which may guide the future material and technology development.