MINING CHEMICALS separation in two ways , either : n “ Using depressants such as sulphites , SO 2 , starch , dextrin , carboxymethyl cellulose or dichromate to depress lead and float copper , or ; n “ Using cyanide to depress copper and float lead .” Both options have drawbacks , according to Solvay . In the first scenario , depressant solutions must be carefully prepared daily in order to minimise variability in the process . Dichromate is effective but highly toxic in this case . In the second scenario , the use of cyanide presents several safety , health and environmental hazards , and typically results in copper concentrates with low grades ( circa-16-19 %).
AERO SR 7480 and AERO SR 7490 address the drawbacks of conventional Cu-Pb-Zn or Pb-Zn modifiers , according to Solvay .
“ Compared to cyanide and dichromate chemistries , SR series reagents are safer to handle and they do not require preparation , which results in less chemical handling exposure ,” it explains . “ Widely applicable to copper , lead and zinc , they offer low dosage variability for feed grade and can work over a wide pH range .”
These reagents can also reduce the consumption of hazardous cyanide in the Pb-Cu separation process , Solvay claims , and are also safer than dichromate , which is considered carcinogenic . Other advantages include cost competitiveness compared with cyanide , reduced reagent consumption and improved separation efficiency .
Solvay says it continues to see mines asking for support to fully transition away from NaSH and other hazardous depressants , with recent trials demonstrating promising results .
Laboratory data on various polymetallic ores show that AERO SR-7480 , when used with sulphites to modify pH , can boost the economics of Cu-Pb separation by improving the copper grade and recovery , maintaining lead recovery and improving lead grade . The reagent is set to be proven out in an upcoming plant trial in Mexico .
Clariant aims for full NaSH replacement
Clariant is also seeing industry support for a full transition away from the use of NaSH , recently coming up with a new , efficient solution for copper and molybdenum separation that , it says , fully replaces the reagent in the flotation process .
FLOTICOR™ DP sulphide depressants are proven in commercial production of molybdenum concentrate , allowing operators to eliminate the risk of NaSH exposure while maintaining molybdenum recovery and grade , according to Clariant . In addition , FLOTICOR DP sulphide depressants can prove effective at a lower dosage than NaSH , providing a cost-effective alternative to the chemical additive .
The main benefits that come with its application , Clariant says , include : n Eliminates the risk of NaSH exposure in all process conditions ; n Maintains the molybdenum recovery and grade ; n Is both odourless and water soluble , and can be used over a wide pH range ; n Enables complete replacement of NaSH , unlike competing alternatives ; and n Easy to implement , using existing plant equipment and flowsheets , and requiring minimal training . Francisco Garcia , North American Business Development Manager and Senior Metallurgist at Clariant Mining Solutions , says FLOTICOR DP sulphide depressants are unique in the sector , compared with all the chemistries out in the market which are only partial replacements for NaSH on an industrial scale .
“ They need NaSH to work because of the mechanism in the flotation process ,” he told IM . “ Our product , however , has already proven that it does not need NaSH .”
A project at a new molybdenum producer in Mexico is where the company has verified this , yet Clariant is also discussing trials with other clients that currently use NaSH as a flotation depressant in molybdenum production .