Exploring the differential effect of adsorption ingredients in three green sorption media for phosphorous removal from river water

Abstract

In this study, three specialty adsorbents (i.e., green sorption media), clay-perlite and sand (CPS), zero-valent iron and perlite-based green environmental media (ZIPGEM), and biochar, zero valent iron, and perlite-based green environmental media (BIPGEM), were studied for their maximum phosphate adsorption capacity (qm) and their performance under different water matrices (i.e., pH of 4, 7, or 10 and canal water spiked with nitrate). The ZIPGEM media mix outperforms BIPGEM and CPS media in terms of phosphate adsorption capacity. According to the Langmuir isotherm model, the qm of ZIPGEM is 1.83, 1.80, 0.947 and 1.78 mg·g−1 at a water matrix of pH at 4, 7, or 10 and when using canal water spiked with nitrate, respectively. Moreover, we observed PO43− removal rates up to 99 % by ZIPGEM and BIPGEM regardless of the nature of the initial water matrix (pH variance and concurrent elements). Given the equivalent performance of BIPGEM and ZIPGEM, we conducted two fixed-bed column studies with ZIPGEM and CPS for further comparison of dynamic adsorption capacity in which CPS was the control. The predicted maximum adsorption capacity of ZIPGEM by the fixed-column study was estimated as 7.56 mg·g−1 in accordance with the Thomas dynamic model, which is higher than that of CPS (3.73 mg·g−1). Our results suggested that the sustainable and scalable nature of the proposed specialty adsorbent ZIPGEM with high phosphate adsorption capacity can be integrated into various water treatment processes. The high adsorption capacity of ZIPGEM can be mainly attributed to higher porosity and BET surface area of ZIPGEM.