Abstract
— The depletion of the sulphide-bearing PGM ores has brought about significant interest in exploring the need to treat oxide-bearing PGM ores, which are discarded and stockpiled. This has led to alternative methods of processing oxide PGM ores as they are not easily recovered via conventional flotation processes. Leaching of oxide PGM ores has led to the study of adsorption techniques to recover PGMs from solutions. Preparation for a bio-adsorbent was conducted using an agricultural waste, macadamia nutshell biomass. Particular attention was paid to the characterization of the raw macadamia nutshells, with XRF, XRD, SEM, FTIR, BET and proximate analysis. Following preparation, macadamia nutshell biomass was subjected to pyrolysis to produce biochar that would be used as an adsorbent for adsorption studies. The XRF analysis of the raw macadamia nutshell showed the presence of the dominant elements such as Fe, Zn, K, Si, Ca, S, Al and Mg, indicating an abundance of inorganic material, which is typical of biomass material. The XRD analysis revealed that the macadamia nutshell had a predominantly amorphous structure, which is typical of the natural organic biomass components of cellulose and lignin. The SEM analysis displayed the surface topography of the raw macadamia nutshell, which is composed of irregular, angular particles with a compact, coarse texture and limited porosity. The EDS results showed that the surface was dominated by 59.86wt % carbon and 39.26 wt% oxygen. The determination of functional groups by FTIR analysis showed the presence of hydroxyl, carbonyl, and hydrocarbon chain groups. Furthermore, the proximate analysis showed the sample exhibited a high content of volatile matter, surpassing 80%, a moderate moisture content of 10-12%, a low fixed carbon content of 6-8% and extremely low ash content of 0.75%. The results obtained from characterization were used to understand the suitability of the biosorbent for PGM adsorption studies.