A review on conventional and novel adsorbents to boost the sorption capacity of heavy metals : current status, challenges and future outlook

Abstract

ABSTRACT Heavy metal contamination in aquatic environments has attracted global concern due to its detrimental impact on living organisms, including toxicity and carcinogenicity. Therefore, initiatives to remove these contaminants from wastewater to protect both the environment and the well-being of humans is imperative. Materials utilized for wastewater treatment in the developing world needs to satisfy the main criterion of being locally available, inexpensive and that do not require additional energy input or modifications. Adsorption is the foremost used technique to eliminate heavy metals due to its attractive features including flexible design, operation, and cost-effectiveness. This review article potentially focusses on the use of novel and conventional adsorbents such as g-C3N4, graphene, cellulosic aerogel, natural occurring soil and minerals, aquatic and terrestrial biomass-based adsorbents for heavy metal adsorption, whilst focusing the discussion on the context of the developing world. This heightened interest in g-C3N4, and graphene-based adsorbents owes their unique properties such as great surface area, impressive chemical and thermal stability, three-dimensional structure, and functionalized derivatives which have shown great adsorption capabilities for heavy metals elimination. Additionally, cellulosic aerogel, natural occurring soil and minerals, aquatic and terrestrial biomass is low cost, easily available and effectively removes heavy metals. Finally, current progress, major challenges and future outlook of novel and conventional adsorbent materials for heavy metal removal are discussed. Herein a roadmap is presented together with recommendations for future research to enhance the successful utilization of bio-sorbents in water purification systems such as wastewater treatment plants.