Elimination of fluoride, arsenic, and nitrate from water through adsorption onto nano-adsorbent: A review

Fluoride, arsenic, and nitrate are considered as major pollutants of water around the world, affecting millions of people mainly through the potable groundwater. Presence of these contaminants in drinking water can cause health issues like dental fluorosis, skeletal fluorosis, blackfoot disease, blue-baby syndrome, reproductive disorders, skin cancer, thyroid dysfunction, hypertension etc. The removal of fluoride, arsenic, and nitrate is mainly carried out through ion-exchange, membrane, adsorption, and other chemical treatments. Owing to the cost competitiveness, energy consumption and customized operating procedure, adsorption has been a popular choice for the removal of these contaminants. The adsorbent based on natural material either in native form or modified at the surface, have gained the momentum to be utilized for fluoride, arsenic, and nitrate free drinking water because of their adequate disposability. Recently, adsorbent of nanomaterial has shown the significant potential for water treatment because of their higher surface area and tailored selectivity. Nanoadsorbents prepared by wet-chemical precipitation, co-precipitation, sol-gel, electro-coextrusion, hydrothermal, thermal refluxing methods etc. can be effectively employed at comparatively lower concentration for water treatment. The adsorption capacity, durability, recyclability, and toxicity of nano-adsorbent are further explored particularly, at commercial scale. The present article is mainly aimed to provide a comprehensive review about the applicability and challenges associated with the use of nano-adsorbents for the removal of fluoride, arsenic, and nitrate with a brief discussion on options and future perspective to meet the challenges of complexity for the selection of environment-friendly adsorbents.