Abstract
Carbon-based catalysts can assist the oxidative leaching of sulfide minerals. Recently, we presented that AF 5 Lewatit® is among the catalysts with superior enargite oxidation capacity and capability to collect elemental sulfur on its surface. Herein, the effect of acid pre-treatment of the AF 5 catalyst was studied on the AF 5 surface, to further enhance the catalytic properties of AF 5. The AF 5 catalyst was pretreated by hydrochloric acid, nitric acid and sulfuric acid. The results showed that the acid treatment drastically changes the surface properties of AF 5. For instance, the concentration of quinone-like functional groups, which are ascribed to the catalytic properties of AF 5, is 45.4% in the sulfuric acid pre-treatment AF 5 and only 29.8% in the hydrochloric acid-treated AF 5. Based on the C 1s X-ray photoelectron spectroscopy (XPS) results the oxygenated carbon is 30.6% in the sulfuric acid-treated AF 5, 29.2% in the nitric acid-treated AF 5 and 28.3% in the hydrochloric acid-treated AF 5. The nitric acid pre-treated AF 5 resulted in the highest copper recovery during the oxidative enargite leaching process, recovering 98.8% of the copper. The sulfuric acid-treated AF 5 recovered 97.1% of the enargite copper into the leach solution. Among different leaching media and pre-treatment the lowest copper recovery was achieved with the HCl pre-treated AF 5 which was 88.6%. The pre-treatment of AF 5 with acids also had modified its elemental sulfur adsorption capacity, where the sulfur adsorption on AF 5 was increased from 30.9% for the HCl treated AF 5 to 51.1% for the sulfuric acid-treated AF 5.
Highlights
Carbon-based catalysts (CBCs), such as activated carbon (AC) and AF 5, are porous catalysts with high surface area and high chemical resistance
The catalytic effect of carbon-based catalysts such as AF 5 in leaching processes is attributed to their surface functional groups, and chemical pre-treatment is a viable method to alter the functional groups on the surface of catalysts
The oxygen functional groups that form with the oxidative pre-treatment results in the formation of more oxygen double bonds such as quinone groups which can significantly increase the catalytic capability of AF 5 for oxidation reactions
Summary
Carbon-based catalysts (CBCs), such as activated carbon (AC) and AF 5, are porous catalysts with high surface area and high chemical resistance. The catalytic properties of the CBC in the oxidative leach processes is resulted from to the functional groups on its surface [3,4,5]. Through chemical pre-treatment processes it is possible to increase the density of the functional groups on the CBC surface and improve its catalytic proppeerrttieess. This is of high interest for chemiccaall pprroocceessssiinnggaannddeexxtrtraacctitviveemmeetatalllulurgrygyinidnudsutsrtyryasatshtehcehcehmemicaiclaplrpe-rter-etartematemntenptropcreoscseesssceasncabne lboewlocwosct opsrtopcersosceessstoesimtopilmempleenmt;eonft;eonfthene pthre-ptrreea-ttmreeantmt pernotcpesrsocinevssolivnevsoolvnelsy orenalyctirnegactthinegCtBhCe CwBitCh awnitohxyagnenoaxtyedgeancaidteidc soacluidtiiocns, osulucthioans,susulfcuhricasacsidulsfoulruictioanc.idInsaodludtitioionn. The aim of the present study was to investigate the effect of different acidic chemical pre-treatment and leaching environments on the surface functional groups and oxidation capability of AF 5. The AF 5 efficiency in the leach tests was studied by the analysis of the leach test solutions to evaluate the copper dissolution efficiency, and the speciation of copper, iron, arsenic, and the sulfur adsorption by the AF 5 catalyst
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