Determination and Removal of Phosphate and Nitrate from the Ground and Surface Water at the Three Counties of Guyana

Abstract

Standard analytical procedures that are based on colourimetry facilitated the determination of PO43- and NO3- in the ground and surface waters from the three (3) counties of Guyana. Phosphates and nitrates beyond their permissible levels in natural waters can pose significant threats to the aquatic environment, its inhabitants, and the health of humans and terrestrial animals. For this reason, this study aims to investigate the use of metal (nickel, cadmium, cobalt) ferrocyanides (octahedral complexes that facilitate adsorption of anions primarily on its two divalent transitional metals) as adsorbents to facilitate the removal of the aforementioned anions. Results revealed that nickel ferrocyanide is the most effective adsorbent for treating ground and surface waters that contain high levels of PO43-, while it was also the most effective adsorbent for treating surface waters that contained NO3-. Fixed volumes of water samples were treated with 50 mg, 100 mg, and 150 mg of the adsorbent. The correlation coefficient computations revealed that they were instances of both positive and negative correlations, which implied that increasing adsorbent dosage resulted in increased adsorption and other instances decreased adsorption, respectively. This occurrence went against literature, possible reasons for this are explained in detail within the discussion portion of the manuscript. Adsorption isotherms and Langmuir plots were used to facilitate adsorption studies, in various instances, the generic appearance of these isotherms was not observed, possible reasons for this occurrence are also explained in more detail within the article. Based on observations within the article, the use of cobalt ferrocyanide for treating groundwater and removing PO43- is not recommended, while cadmium ferrocyanide is not recommended to be used to facilitate the removal of NO3-, due to the possible formation of Co3(PO4)2 and Cd(NO3)2, respectively, which consequently affected the results. Technologies like those studied in this research project should be explored and studied more in-depth (particularly with regards to the stability of the adsorbents) with regards to the treating of ground and surface water supplies, to facilitate the removal of PO43- and NO3-, since the results observed, though on a small scale, can be seen to move us closer towards a green and sustainable environment, inclusive of safeguarding the health of the Worlds’ people and expanding the scope of cost-effective and simple methods that aid in the removal of anions from natural waters.