Rhodochrosite Leaching Based On Surface-interface Enhancement

China played a dominant role in global electrolytic manganese metal(EMM)production.However,there is a shortage of manganese rich resources in China.Energy and material consumption of EMM production is high,and the emission of pollutants is also great.Therefore,it is of strategic significance to study a green,efficient and low-consumption method for enhanced extracting manganese to alleviate manganese ore shortage in China and thus to promote a healthy and sustainable development of electrolytic manganese industry.Electrolytic deposition with rhodochrosite as raw material is the main method to produce manganese metal,but rhodochrosite grade in China is low with poor quality,which is usually show a high vein content and co-exists with multiple mineral phases.Thus it is difficult to achieve efficient leaching of manganese by direct acid leaching.In this thesis,based on the analysis of the mineralogical characteristics of rhodochrosite before and after leaching,surface-interface enhanced rhodochrosite leaching is proposed by modulating CaSO₄·2H₂O passivation layer morphology and by reducing its crystallinity via surfactant.Meanwhile,the introduction of ultrasonic renews the solid-liquid interface,opens the mineral inclusions,and promotes the solid-liquid interface mass transfer to achieve enhanced leaching of manganese rhodochrosite.The main findings are as follows.(1)The mineralogical analysis of typical rhodochrosite shows that the structure of rhodochrosite in China is complex,and rhodochrosite is closely symbiotic with dolomite,calcium magnesium carbonate,calcium zeolite and clayey matter,forming multi-mineral inclusions.Among them,the symbiosis of dolomite,calcium magnesium carbonate and rhodochrosite leads to CaSO₄·2H₂O passivation layer in the leaching process.The mineral inclusions,clayey matter hinder the solid-liquid mass transfer process,and the leaching solution is difficult to act directly on the target minerals.(2)A surfactant interface-enhanced rhodochrosite leaching study was carried out.The results showed that the relationship between the effective thickness?(mm)of CaSO₄·2H₂O passivation layer at the interface of rhodochrosite leaching process and the dissolution of ore particles is?=(0.741-b)/S(S is the dissolved area;b is the dissolved mass).The surface-interface enhanced leaching revealed that the surfactant trisodium citrate(TC)could reduce the crystallinity of CaSO₄·2H₂O crystals 020,040 and 041 faces,decreasing the thickness of the crystal faces,and enhancing the solid-liquid mass transfer area.Under the conditions of 5mg/L TC,solid-liquid ratio of 1:5 g/L,acid-ore ratio of 0.5:1 g/g,3.5 h and 50?,the leaching efficiency of Mn was 91.23%,which is 13.82%higher than the leaching without TC under the same conditions.(3)The effect of ultrasonic enhanced interfacial mass transfer on the leaching of rhodochrosite was examined.In the ultrasonic external field enhanced interfacial mass transfer,comparing with conventional leaching,it was found that ultrasonic could open mineral inclusions,inhibit CaSO₄·2H₂O crystallization,and promote solid-liquid interface renewal to achieve enhanced leaching of rhodochrosite.When combined with Carman-Kozeny suspension percolation velocity analysis,it shows that the acoustic cavitation effect makes the rhodochrosite slurry in the ultrasonic field possess higher suspension,the mineral particles have richer pore structure and higher percolation efficiency at the solid-liquid interface.The leaching efficiency of Mn was 94.09%at a solid-to-liquid ratio of 1:5 g/L,an acid-ore ratio of 0.58:1 g/g,and an ultrasonic power of 60 W at 50°C for 2.5 h.The leaching efficiency of Mn was increased?7%compared with that of no ultrasonic leaching under the same conditions,which further shortened the leaching time and improved the leaching efficiency of Mn.(4)The synergistic ultrasonic leaching of manganese rhodochrosite with surfactants was investigated.Ultrasound combination with the surfactant sodium dodecyl sulfate(SDS)show a bubbling effect.Sodium oleate(SOL)was able to enhance the suspension of the pulp and shorten the leaching time of rhodochrosite to 2 h,and the leaching efficiency of Mn was increased?17%compared to the leaching with sulfuric acid under the same conditions,significantly improved the leaching efficiency.