Modelling of the elution process

Abstract

The inffuariCa of'temperature on the equilibrium adsorption of gold and hydroxide ion at elution conditions was examined. Experiments. wercr"C(mduct~d for .R21!1 siQgle and mUltiple' solute adsorption of gold and OH' ion at the temperatures between 80 and 120°C. For gold concentration levels of betv/een 0 and 600ppm were treated while the hydrQxide ion CQi1~~ntr.at1M!a\iel, was '? .... " .. . . tr . -e-, betwesn 0 and a.arvl., \\ "0;, ! o· Three (nodeIS'We(~ emp\byed tOlmodel the equilibriuty1 ~dsorp~on of each solute at the single ~~Y'i,lJe level. These consis,t oHhetreundlioh isotherm1fF1)dhe Modifieq Freundlich isotherm (MFI) arltIJhe " Linearized for~ of the MFr(L.MFI). The Modified Freundlich isotherm allowed 'the asnr.1ation of the Q change in the fte,at of reaction of adsorptrQn, &H, and for gold L\H of ·42.63kJ/mal was estimafed while -14.86kJ/mol was.estimated forOH', These figures,'obtained confirmed that the. adsorptionD process is significantly a physlcal.on~, In the case of the multipt~ solute~adsorptkm, the Freundlichtype mode! and a General empirical multi-solute model yl{as Used for the modelling. :, \ \ 'l '___- _ ___ I '}~\' _ _ _ ____ _ _-= Rigorous statlsticalmethods were employed to discdmiriate betNeen the models. It was foundtnat forthe single-solute adsorption, thE!"Modified Freundlich isotherm is tha best modelANhile Jorthe multiple-$~Iute adsorption, the ~enG\fal empirical model was better than the Freundlich-tYpe model. ~ 0 Kinetics of elution data were also generated with models depending upon surface diffusion and film transfer also developed. A plu~ flow model was also ,developed and shnplifled using the method of ,characteristics. These models were solved simultaneously coupled?;ao the Modif.~·;d Fr,eundlich isotherm to simulate the exgerimental data obtained. It was obselVed that the mod!~1was less sensitive to the diffusion cq"gtficient bence~Gt1t1ace diffusion was eliminated. Thi~ rnodifiootion Jmplies, that only film. trans~r affects the process:~jThe fiI~'transfer contralled.,n)odel was fOU~ to represent the expenmental data very ,well.,