Amine-grafted Walnut Shell for Efficient Removal Phosphate and Nitrate from Aqueous Solution

Abstract

The presence of emerging pollutants such as PO43− and NO3− in water bodies has attracted worldwide concern about their severe effects on water bodies and the health of humankind in general. Therefore, to preserve the health of humankind and environmental safety, it is of the essence that industrial effluents are treated before they are discharged into water bodies. To accomplish this, the walnut shell was functionalized (ACWNS) with amine for effective removal of PO43− and NO3−. Characterization studies of ACWNS were conducted using FTIR, XRD, XPS and BET techniques. Removal of both ions was enhanced at lower temperature (293 K). The maximum uptake capacity of phosphate and nitrate, at 293 K, was 82.2 and 35.7 mg g− 1, respectively. The primary mechanism by which these ions were uptaken onto ACWNS could be electrostatic interactions and hydrogen bonding.Pseudo-second-order kinetics fitted the PO43̶ and NO3− adsorption, while Freundlich and Langmuir models best fitted the PO43̶ and NO3̶ adsorption, respectively. Furthermore, in the binary system, the uptake capacity of phosphate decreased by 14.4% while nitrate witnessed a reduction in its uptake capacity by 10.4 %. So ACWNS has a higher attraction towards both ions and this could be attributed to the existence of a variety of active areas on ACWNS that exhibit a degree of specificity for the individual anions. Results obtained from real water samples analysis confirmed ACWNS as highly efficient to be utilized for practical remediation processes.