Energy Extraction From Heavy Metals And Pollutants Removal

Heavy metal is a kind of common environmental pollutant.It is a great threat to theecological environment and human health.On the other hand,heavy metals,especially gold andsilver has a high economic value,so the recovery of heavy metals from the pollutants havebroad prospects.Current technologies for heavy metal treatment and recovery are oftenenergy-intensive and may cause secondary pollution.To find an effective way to directlyconvert the chemical energy to electricity and recover precious metals/heavy metals in thesame time will become a hot topic.In this paper,heavy metal coupled redox fuel cell(HMCRFC)was designed,typicallyselecting urea-Cu(?),ethanol-Au(?)/Cu(?)and ethanol-Ag(?)/Cu(?)redox,to convertchemical energy in fuel and oxidant directly into electricity and simultaneously achieverecovery of heavy metals.The basic research on no energy-consuming treatment and recovery ofpollutants was carried out.Ni/C and Pd-Ni/C catalysts were prepared and characterized by using electron microscopy,X-ray diffraction,X-ray photoelectron spectroscopy and electrochemical measurements.Aunique photoelectrolytic cell was newly designed combining with Raman spectroscopy andelectrochemical information detection to verify the catalytic mechanism of Ni-based catalyst.Urea-Cu(?)CRFC was succesfuly assembled.When copper ion used as the oxidant in thecatholyte with the fuel of urea in NaOH,it can produce an open circuit voltage of 1.06 V,meanwhile,elemental copper formed on the cathode.Applying 400 mg L-1 in catholoyte,itwould produce energy that is equivalent to ca.6.1 kWh kg-1 copper.At this situation,90%removal of Cu(?)was achieved after 24 h running.Au(?)/Cu(?)and Ag(?)/Cu(?)mixed solution were used as the catholyte to investigatethe deposition and removal of heavy metals in the cathode.The results show that the two kindsof heavy metals with different reduction potential can be effectively separated and recoveredand generate the electricity simultaneously.Thus,Cu(?),Au(?)/Cu(?)and Ag(I)/Cu(?)in the CRFC can directly produce electricity,and heavy metals can be simultaneously removed.In addition,this system achieves separation recovery of multiple metals when two or more metals coexist to be oxidants in the catholyte of CRFCs.This approach is expected to become a new technology for heavy metal treatment.