Title page for ETD etd-10212005-123010


Type of Document Dissertation
Author Kim, DongSu
URN etd-10212005-123010
Title Studies on the reactivity of thiophosphate/thiophosphinate and ethyl xanthate with precious metals
Degree PhD
Department Materials Engineering Science
Advisory Committee
Advisor Name Title
Yoon, Roe-Hoan Committee Chair
Adel, Gregory T. Committee Member
Luttrell, Gerald H. Committee Member
Nagaraj, D. R. Committee Member
Reifsnider, Kenneth L. Committee Member
Richardson, P. E. Committee Member
Keywords
  • Precious metals.
  • Ethyl xanthate.
  • Thiols.
  • Thiophosphates.
  • Adsorption.
Date of Defense 1992-12-05
Availability restricted
Abstract

Adsorption mechanisms of modified thiol collectors on gold, silver, and gold-silver alloys have been studied and compared with those of ethyl xanthate (EX). The modified thiol collectors include dicresyl monothiophosphate (DCMTP), dialkyl dithiophosphinate (DTPI) and monothiophosphinate (MTPI). In general, the adsorption mechanisms on silver and gold-sil ver alloys can be explained by the EC-mechanism involving an electron transfer step and a chemical reaction step. Thus, the adsorption should be controlled by the Eh of the electrochemical oxidation of the electrode involved and the pK of the metal collector complex. According to this mechanism, DCMTP should adsorb on silver and gold-silver alloys at a lower potential than DTPI and MTPI since the pK of sil ver-DCMTP complex is larger than those of silver-DTPI and silver-MTPI. This has been verified to be the case by voltammetry, FTIR and contact angle studies. Likewise, EX adsorbs on silver at a lower potential than the modified thiol collectors because the pK of silver-EX is larger than those of the silvermodified thiol collectors.

Both EX and the modified thiol collectors adsorb on silver at lower potentials than on the gold-silver alloys, which can be attributed to the lower activity of silver on the alloy surface. For the same reason, the potential for the onset of collector adsorption on alloys decreases with increasing silver content.

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