Professor Yongjun Peng


School of Chemical Engineering
Faculty of Engineering, Architecture and Information Technology
+61 7 336 57156


Yongjun Peng is a Professor at School of Chemical Engineering, The University of Queensland. He obtained his PhD under the supervision of Profs Stephen Grano, John Ralston and Daniel Fornasiero from the Ian Wark Research Institute of the University of South Australia in 2002. This study was part of a large international project, AMIRA P260C regarding grinding and flotation chemistry in fine particle flotation with application of complementary solution and surface analytical techniques. He studied the galvanic interactions between grinding media and base metal sulphide minerals, mineral oxidation and dissolution, the activation of iron sulphide minerals, and surface contamination in improving mineral flotation. He was the 1st researcher developing the well-known Magotteaux Mill which allows the control of chemical reactions during grinding. His research work also guides the industry to use high chromium media in primary grinding mills and inert grinding media in regrinding mills to minimize the negative effect of galvanic interactions.

From 2002 to 2006, Yongjun Peng worked at the COREM Research Centre in Canada which is supported by the Canadian government and eleven international member mining companies. During his time there, he developed technologies for member mining companies to improve base metal, gold and niobium flotation. He was awarded an expert certificate for five years in Canada by the Quebec government, and also awarded NSERC (Natural Sciences and Engineering Research Council of Canada)-Industry Research Fellowship. From 2006 to 2009, Yongjun Peng worked at BHP Billiton Perth Technology Centre in Australia as a Senior Metallurgist/Engineer responsible for fine nickel flotation in saline water, gold and uranium processing. He won a major BHP Billiton internal prize in 2008.

Yongjun Peng’s current research at the University of Queensland focuses on froth flotation and the underlying solution chemistry, colloid/surface chemistry and electrochemistry. In addition to solving problems for individual companies, the underlying theme is the particle interaction taking place during the processing of low quality and complex energy and mineral resources with low quality water to address key challenges that face the resource industry today. His research is supported by the Australia Research Council, the Australian Coal Industry’s Research Program (ACARP) and the resource industry. In 2022, he was awarded the ACARP Research Excellent Award recognising research and leadership excellence through long term commitment and impact.

New technologies developed

Depressing hydrophobic gangue minerals in the flotation of sulphide ores. Traditional prefloat to float and remove hydrophobic gangue minerals also floats and removes sulphide minerals due to the collectorless flotation of sulphide minerals upon surface oxidation. This technology introduces a prefloat cleaner stage where sulphide minerals recovered to the prefloat concentrate are depressed and separated from other hydrophobic gangue minerals at a low pulp potential using innovative reducing agents which do not affect the natural floatability of sulphide minerals. The prefloat cleaner tailings are then fed back to the main sulphide flotation circuit. Traditional reducing agents applied in prefloat require high consumptions and also interfere with the downstream flotation. Flotation tests using chalcopyrite and organic carbon show that the new approach can reduce the loss of chalcopyrite in the prefloat by over 40% without affecting the rejection of naturally hydrophobic gangue. This technology is commercialized by ALS.

GoldRecover. This technology improves the gold flotation recovery from comminution circuit and flotation circuit in gold processing operations using innovative chemicals to remove iron contamination from gold surfaces. Iron contamination prevents the adsorption of collectors on mineral surfaces. Based on a copper-gold ore, this technology achieved a gold recovery up to 30% and a copper recovery up to 12% higher than the base line. Based on a pyrite-gold ore, this technology achieved a gold recovery up to 10% higher than the base line. This technology is commercialized by Kinetic Group Worldwide.

Counteracting the adverse effect of cyanide in flotation. Cyanide added to depress gangue minerals or existing in process water can depress the flotation of sulphide and precious minerals. Cyanide can also complex with metal ions and form metal cyanide which can depress or activate mineral flotation depending on the pulp chemistry. The new technology involves the modification of pulp chemistry to make metal cyanide activate sulphide and precious minerals in flotation. This technology has been applied in the sponsor’s flotation plant to improve gold and silver recoveries since 2012.

Regrinding-flotation pre-treatment prior to CIL leaching. This technology has been applied in the sponsor’s plant to improve copper and gold recoveries while reducing cyanide consumption since 2012.

New sulphidisation to improve the flotation of oxidized minerals. Traditional sulphidisation suffers from drawbacks such as low efficiency, low pulp potential with a high reagent consumption and difficulty to sulphidise some minerals. The new sulphidisation we developed from the ARC Linkage Project LP160100619 supported by Newmont and Newcrest is conducted at higher pulp potential. Based on a stockpile copper ore, the new sulphidisation improves the copper recovery from 76% (base line) to 93% with even higher copper grade. Based on a stockpile pyritic ore containing gold, the new sulphidisation improves the recovery of total S from 48% (base line) to 68% and the recovery of sulphide S from 84% (base line) to 92%.

De-aerating froth products (patented technologies). Persistent froth in flotation concentrates presents operational challenges in downstream processing such as pumping in sumps and dewatering in filters and thickeners. In sumps where flotation concentrates are pumped to the dewatering process, the liquid level sensors often fail to detect the persistent froth which may lead to flooding of the processing area or even the entire plant. In dewatering to separate the solids in the concentrate from water, persistent froth significantly reduces both thickening and filtration efficiencies. The accumulated persistent froth floating on top of thickeners can also limit the capacity of the plant. Two types of physical froth de-aerators have been developed, one based on physical forces and another based on pressure changes. The de-aerator using physical forces is suitable for destabilising froth in sumps and filters, while the de-aerator using pressure changes is suitable for destabilising froth in thickeners. These technologies are commercialized by DADI (AUSTRALIA) Engineering Company.

Rapid measurement of coal oxidation (patented technology). This technology can be used in the plant to determine the degree of coal oxidation in natural environments within 5 minutes. The solvens used are environmentally friendly. Based on the degree of coal oxidation, a ratio of non-polar collector to polar collector can be determined to maximise the coal flotation while minimizing reagent consumptions. At one coal preparation plant this technology demonstrates an improvement of 5%-26% increase in the recovery of coal (based on applying optimised ratios of oily and polar collectors for the measured degree of coal oxidation).This technology is commercialized by interchem.

Apparatus and method for emulsifying oily collectors for use in flotation (patented technology). Oily collectors are widely used in the flotation of various commodities. Due to their low solubility in water, a large amount of oily collectors has to be used with a long conditioning time. A number of studies has demonstrated that chemical emulsifiers can significantly improve the efficiency of oily collectors by reducing their droplets. However, the application of chemical emulsifiers in flotation plants is limited due to their strong frothing abilities which can cause various problems. We have developed apparatus to physically emulsify oily collectors to droplets with a size ranging from 12.2 µm to 0.7 µm and found that the flotation performance increases with the decrease of droplet size until an optimal droplet size. Droplets smaller than the optimal size is not beneficial to flotation. The apparatus has a low equipment cost and low maintenance. Based on the test work on five different coal samples from 3 Australian coal preparation plants, the emulsified diesel could increase the yield by 2.5 to 15.3% at the same product ash content while reducing the diesel consumption by 97,412 L to 304,941 L per annum. This technology is commercialized by DADI (AUSTRALIA) Engineering Company.

Research Interests

  • Regrinding Chemistry
    Yongjun Peng’s research addresses regrinding chemistry to identify how particle breakage mechanisms in tumbling mills and stirred mills affect pulp and surface chemistry and the redistribution of surface oxidation species, activation species and flotation reagents in improving mineral flotation and separation. He have developed a new regrinding-flotation process to improve copper and gold recoveries prior to CIL while reducing reagent consumption in flotation and cyanidation. Presently, his research focuses on mitigation of negative effects of pulp chemistry after fine regrinding on the adsorption of collectors on value minerals and the activation on gangue minerals.
  • Green Flotation Chemistry
    The research aims to overcome the drawbacks of natural products when applied in industry, i.e., low solubility and low selectivity, by designing modified macromolecules and understanding the role of their structure features in mineral flotation. His group has successfully modified lignosulphonates and wheat starches to produce macromolecules which vary in molecular weight distribution and functional group content. The group discovered that a chelating type bond centred on mineral surfaces determines the adsorption of modified polymers and the conformation of supramolecular and molecular structures of the polymers are more influential than functional groups for depressing minerals. At the same time, his group had an initiative to develop a new type of green collector for gold flotation based on Eucalyptus oils extracted from Eucalyptus to replace toxic collectors used in gold flotation. The group found that the collecting power of Eucalyptus oils is correlated to the percentage of non-polar and weakly polar constituents which possess strong selectivity for free gold.
  • Particle and Reagent Interactions in Low Quality and Saline Water
    This work not only identifies the different particle interactions in saline water, but also addresses the different behaviour of flotation reagents (collector, frother, polymeric dispersant and flocculant) in saline water. Novel reagents have been developed to be used in saline water to mitigate slime coating, gangue entrapment and overly stable froth. Yongjun Peng is also working on cyanide chemistry and the interaction of free cyanide and WAD cyanide in recycle water with base metal sulphide and precious minerals. New technologies have been developed to counter the depression of cyanide species in process water on the flotation of pyritic gold. Cyanide speciation is also manipulated to enhance the depression or activation. In addition, his group discovers that the low dissolved oxygen content and the low electrochemical potential in saline water promote copper activation on pyrite, leading to a low grade of copper flotation concentrates. Based on this finding, a radical chain reaction involving the redox cycling of Cu(I/II) induced by sulphite has been developed to de-activate copper activation in saline water.
  • Ultra-fine Particle Flotation
    Yongjun Peng has been working on oxidation and dissolution of fine sulphide minerals and how these alter surface characteristics and affinity to other gangue minerals and colloids governing the bubble-particle attachment efficiency. He has also worked on strategies to control the oxidation of fine particles and their interactions with other gangue minerals and colloids in improving ultra-fine particle flotation. He has developed a simple chemical process to clean the surface contamination to improve copper and gold flotation. Presently, he starts a new research program to improve fine particle flotation by engineering the surface properties, and develops simple tools to measure surface oxidation in plants.
  • Gangue Chemistry
    This work explores slime coating of fine gangue minerals, the entrainment of normal gangue minerals through the water films of gas bubbles and the entrapment of anisotropic gangue minerals through network structures in flotation. Yongjun Peng’s research addresses how slimes coat mineral surfaces and how anisotropic minerals form network structures under flotation context and then affect pulp rheology and subsequent mineral flotation and gangue entrapment. He also works on strategies to mitigate slime coating and reduce particle entrainment and entrapment by modifying particle interactions and network structures through polymers and inorganic salts. Simple tools have been developed to characterize clay minerals.


  • Doctor of Philosophy, University of South Australia


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  • (2024) Master Philosophy

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  • Doctor Philosophy — Principal Advisor

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  • Doctor Philosophy — Principal Advisor

  • Doctor Philosophy — Principal Advisor

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