MINING CHEMICALS
Finding the formula
The mining sector ’ s ESG focus continues to lead mining companies down a new , cleaner path with the use of chemicals another area ripe for disruption . Dan Gleeson looks at some of the pioneers changing the status quo
Similar to the revolution taking place in the mobile mining equipment space with the replacement of diesel , the chemicals sector is undergoing a sea change that could see significant replacement of reagents once deemed irreplaceable in the flotation plant or leaching arena .
Catalysed by a remit of improving the working conditions of employees previously exposed to hazards while making their products as ethical as possible , mining companies are coming to chemical suppliers in need of sustainable solutions .
This is seeing chemical specialists re-evaluate their R & D portfolio , realising that the investment case for new reagents now includes more than just the straight-forward economic parameters that previously populated excel spreadsheets .
Depressants with a difference
Lower-grade ores usually contain penalty elements that negatively impact revenue because of high smelting costs .
Arsenic-bearing minerals such as arsenopyrite and tennantite are probably the most common impurities in copper deposits and , arguably , the hardest to remove as arsenopyrite floats in a similar fashion to chalcopyrite , according to Solvay . Arsenic in copper concentrates reduces product purity , increases cost in the smelting process and is harmful when released in the environment .
Recently , Guangxi University in China conducted a study on Solvay ’ s organic polymer AERO ® 7261A showing its high selectivity and excellent depression on both pyrite and arsenopyrite , the company reported . In this study , AERO 7261A replaced sodium sulphite ( Na 2SO 3 ) in the separation of Cu-S-As bulk concentrate from Yunnan Datun Mill during a batch flotation test in a pilot plant . AERO 7261A improved copper recovery by 9.73 % and reduced the arsenic content to 1.02 % in the copper concentrate .
Beyond China , AERO 7261A has also been used as pyrite and arsenopyrite depressants in various mines in Portugal , Australia and Mexico , Solvay says .
AERO 7261A is not only used as a pyrite and arsenopyrite depressant in Cu-S-As ores ; it is also used in Cu-Pb-Zn and Ni-Cu-Co ores .
In a recent application of AERO 7261A in China on a Cu-Pb-Zn ore with some silver , the lead and zinc recovery improved by about 5-6 %, while silver and copper increased by 10-25 %, Solvay reported . AERO 7261A depressed the pyrite and contributed to reducing high lime dosages , too .
In addition , the reagent enabled a reduction in pH from 12 to 10 , and a reduction of the copper sulphate dosage , allowing the system to operate
Solvay says the mining sector ’ s focus on addressing safety concerns is leading it to expand its line of sustainable depressants
with much lower reagent consumption and better recovery of value metals , the company says .
It is true most of the common depressants used in the mining industry are typically hazardous in their health and toxicity profile , detrimental to both humans and the environment . Yet , Solvay says addressing safety concerns is still the top priority for the mining industry , leading the company to expand its line of sustainable depressants .
The industry has become familiar with Solvay ’ s sodium hydrosulphide ( NaSH ) replacement technology , the AERO NR series ( NR 7260 , NR 7361 and NR 7370 ), which the company says is widely used in copper-molybdenum mines to replace up to 100 % of NaSH , Na 2S and Nokes usage .
Solvay has since introduced AERO SR 7480 and AERO SR 7490 , the company ’ s newest modifiers , to depress copper in Cu-Pb-Zn or Pb- Zn circuits .
“ The processing of polymetallic ores such as Cu-Pb-Zn or Pb-Zn with penalty amounts of copper is challenging due to the difficulty in separating the various sulphides ,” Solvay explains . “ Many plants implement Cu-Pb
26 International Mining | MAY 2023