Existing and emerging technologies for the removal of orthophosphate from wastewater by agricultural waste adsorbents: a review

Abstract

The presence of orthophosphate in water can lead to eutrophication. Eutrophication has become a global environmental issue due to the increasing discharge of orthophosphate into water bodies as a result of increases in agricultural and industrial activities around the globe. Orthophosphate is among the limiting nutrients governing the growth of algae, and excessive release of phosphorus into the aquatic environment has contributed significantly to the eutrophication process. A rational shift is ongoing in wastewater treatment technology due to the need for cheap adsorbents to reduce wastewater treatment costs. The fact that some agricultural waste adsorbents (AWA) show promise in removing orthophosphate from the wastewater lends support to a hypothesis that they can be of a broad-spectrum for industrial applications. As shown in many studies, the affinity of AWA towards orthophosphate water contaminants can be enhanced through physical and chemical treatment, and few studies were performed on the potential of AWA towards the removal of orthophosphate from waste effluent. This article summarizes progress in transforming diverse agricultural wastage (AW) as potential adsorbent candidates for efficacious orthophosphate removal from wastewater over the last few decades. The production methods and the results obtained were discussed comprehensively. Surface modification through physical and chemical treatment, metal loading, and grafting has been proposed to improve the orthophosphate removal efficiency. The adsorption and desorption options’ challenges that need to be considered more in future research include continuous and dynamic mode of adsorption, leaching, and loss of adsorbent material during regeneration and development of suitable models to describe the full range of adsorption with a high concentration of orthophosphate. The AW materials are always available, eco-friendly, and cheap to be used as an adsorbent.