Adsorption of Heavy Metals and Biocides from Building Runoff onto Granular Activated Carbon—The Influence of Different Fractions of Dissolved Organic Matter

Abstract

Building runoff presents a good opportunity for water reuse in urban infrastructures; however, it is often polluted by biocides and heavy metals. In order to mitigate the pollution and improve water quality, we analysed the adsorption of heavy metals and biocides onto granular activated carbon (GAC) and investigated the influence of dissolved organic matter (DOM) fractions (>100 kDa, 10–30 kDa, and 3–10 kDa). In addition to our experimental work, we also studied the adsorption process by applying the Langmuir and Freundlich models. The results showed that ≥50% of DOM was adsorbed at low concentrations (5 mgC/L). We also observed that DOM at a small molecular size exhibits improved adsorption. The adsorption capacity estimated by the Langmuir equation for Cu2+ and Zn2+ in the absence of DOM influence was 157 and 85.7 μmol/g, respectively. The presence of DOM at 5 mgC/L improved the adsorption of Cu2+. Zn2+ adsorption was less sensitive to the presence of DOM than Cu2+. Interestingly, without the influence of DOM, diuron-related compounds have a higher affinity toward GAC than terbutryn-related compounds. DOM affected the adsorption of diuron slightly. For terbutryn, the adsorption was enhanced, whereas mecoprop-p exhibited a strong competition with DOM. The presence of Cu2+ and Zn2+ presented a similar effect on the adsorption of biocides like DOM. Overall, GAC is an ideal adsorbent material for use in retaining building runoff pollutants.