SINGLE AND COMPETITIVE ADSORPTION OF CD AND ZN ONTO A GRANULAR ACTIVATED CARBON

Single and competitive adsorption of cadmium and zinc onto granular ac tivated carbon DARCO 12-20 mesh has been investigated. This activated carbon has been shown as an effective adsorbent for both metals. Cadmi um and zinc removals increased with pH and decreased with molar metal/ carbon ratio. Surface precipitation phenomena have been detected for t he higher pHs and molar ratios. The adsorption process has been modell ed on the surface complexation Triple Layer Model (TLM). For this purp ose, the amphoteric nature of the activated carbon has been studied. S ingle metal adsorption data have been used to calibrate TLM parameters . A dependence of the adsorption constants on pH and molar metal/carbo n ratio has been observed, and a correlation for log K-ads has been de termined. In the competitive system, the removal efficiency of the act ivated carbon decreased for both metals. The TLM model, using surface complexation constants determined from single adsorption experiments, successfully predicted cadmium and zinc removal from the two metal sol utions. Copyright (C) 1996 Elsevier Science Ltd