Efficient phosphate adsorption in aqueous solution using nano-zirconia impregnated spent coffee grounds and preliminary application as a slow-release fertilizer

Abstract

ABSTRACT In this study, the development of a nano-biocomposite adsorbent based on spent coffee grounds (SCG) and nano-Zirconia (n-ZrO2) was presented to meet the increasing demand for effective and low-cost phosphate adsorbents and contribute to sustainable development goals (SDGs). The adsorption performance of raw SCG and SCG modified with n-ZrO2 (n-ZrO2-mSCG) was tested. The characterization of materials was performed by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET surface area analysis, thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), Dispersive X-ray spectroscopy (EDS), and Transmission electron microscopy (TEM). The n-ZrO2-mSCG exhibited superior adsorption capacity compared to SCG. The influences on the adsorption of factors such as initial concentration, pH, stirring time, temperature, and coexisting ions were evaluated. The results showed the maximal adsorption capacity of modified SCG was 15.8 mg/g at pH 2, using a stirring time of 150 mins. Among investigated coexisting anions, sulfate (SO4 2-) and bicarbonate (HCO3 −) affected the phosphate adsorption performance of n-ZrO2-mSCG, when they existed in aqueous solution at predominant levels. The n-ZrO2-mSCG displayed high selectivity toward phosphate and sustained efficacious phosphate adsorption after three successive cycles of adsorption/desorption, proposing a prospective low-cost and reusable adsorbent material for phosphate removal and a potential alternative to conventional fertilizers.