Researchers from Kanazawa University have found that palladium and silver can be recovered from industrial waste, which will save our world by reducing emissions and mitigating demand for dwindling natural resources.
Many metals are becoming increasingly scarce, but there is still a market for their use in electronics, medical equipment, and the manufacture of other products.
Major metals like these contaminate the ecosystem and damage human health.
Ideally, the metals should be recycled and reused from the waste. Recycling approaches are technically complex, costly, harmful, inefficient, and ultimately ineffective.
Researchers at Kanazawa University announce that their new separation technique greatly improves the recovery of silver and palladium ions from aqueous acidic waste. Recovering the metals in elemental, metallic form is easy, just burn the extraction material and collect the remaining metals after further heating.
A team of researchers researched the ability of cellulose fibers to catalyze the reduction of silver and palladium ions.
Adsorption was nearly complete for the pH spectrum from acidic to just below the acidic.
This is an acceptable experimental design.
“The adsorbent selectively chelated the soft acid silver and palladium cations,” states one of the researchers. “Of the 11 competing base metals we tested, only copper and lead ions also adsorbed, but we removed them with ease.”
The most metal-ion adsorption occurred rapidly, such as within one hour. In other methods, full adsorption requires a considerable amount of time.
“Intraparticle diffusion did not hinder adsorption, which is an endothermic, spontaneous chemical process,” said Hiroshi Hasegawa. “The maximum adsorption capacities for metals – e.g., 11 mmol/g for silver – are much higher than those reported in previous studies.”
After adsorption, the researchers were able to extract elemental silver or palladium through a simple method of combustion. The extract was then heated to a higher temperature and converted into smaller crystals.
Alternatives to cyanide or other toxic extracts were not necessary. The lab concluded that the final metals are in metallic form, not oxide.
We extracted much of the silver and palladium from actual industrial waste samples.” After the extraction, the precipitation of all of the pure and elemental metals was as smooth as in our experiments.
Both palladium and silver are essential metals, yet their natural reserves are diminishing rapidly.
Increasing demand demands that we use metals we have already by seeking new applications for them.
The research discussed is a significant advancement that will lead to more reliable supplies and lower delivery costs down the road.
Reference: “Selective recovery of silver and palladium from acidic waste solutions using dithiocarbamate-functionalized cellulose”, by Foni B.
Ismail M. M. Rahman, Keisuke Nakakubo, Koki Yunoshita, Masaru Endo, Kanji Nagai, Asami S. Mashio, Tsuyoshi Taniguchi, Katsuhiro Maeda and Hiroshi Hasegawa. Chemical Engineering Journal. DOI: 10.1016/j.cej.2020.127225.