Re ECF Project : 2005-06

Project Title : Environmentally-friendly nanosorbents for recovery of precious metals from waste effluents
Applicant : Hong Kong University of Science & Technology

Project Proponent : Professor KL Yeung & Professor Gordon McKay
Total Approved Grant : $148,784 (ECF&WWGF: 50/50)
Duration : 1/2/2006 to 30/11/2006
Project Status/Remarks : Completed
Scope :
The purposes of the project are:

  1. To produce and characterize 2-to-3 selective nanosorbents from mesoporous silica;
  2. To test their ability to remove and recover low concentrations of precious metals including gold and silver from waste effluents - microelectronics, metal plating, jewellery wastewater;
  3. To perform precious metal recovery and nanosorbent regeneration studies; and
  4. To undertake a preliminary process design and technical/industrial investigation for full-scale commercial development.

Summary of Findings/Outcomes:
This work established a rational approach in the design and preparation of selective nanosorbents for removal and recovery of precious metals (i.e., silver, gold and palladium) for recycle and reuse.

  1. Nanosorbents that adsorb only gold enabled the recovery of high purity gold (> 90 %) from electroplating wastewater containing high COD (60,000) and TOC (25,000) as well as a myriad of other metals including Co, Mn, Ni, Zn and Cr.
  2. High purity silver (i.e., 99 %) was recovered using a nanosorbent from an electroplating wastewater that has TOC content of 25,000 along with Pb, Fe, Co and Zn.
  3. High purity gold (i.e., up to 99 %) was recovered from simulated gold mining solutions prepared according to the composition provided by Mr. van de Linde of Invid Technologies.
  4. The study showed that the nanosorbents could be regenerated and reused without loss of performance.
  5. Calculation showed that the use of nanosorbents for precious metal recovery is both technically and economically feasible.