Guixia Fan

This paper presents the development of an environmentally friendly, small molecular depressant citrus pectin for improving the recovery of cassiterite resources. Citrus pectin extracted from citrus peel was utilized as the depressant, and it demonstrated significant potential in separating calcite from cassiterite in micro-flotation tests. The molecular weight of the citrus pectin extracted in this paper decreased from 11,485,412 Da to 32,959 Da compared to commercial pectin, resulting in the depressant efficiency of the reagent. The results of a zeta potential and adsorption test indicated that citrus pectin had less and weaker adsorption on the cassiterite surface and could be replaced with NaOL. The chemical adsorption process of citrus pectin on the surface of calcite was determined through FTIR spectroscopy analysis. XPS analysis results indicated that the interaction between the carboxyl groups of citrus pectin and calcium atoms enables adsorption to occur. The AFM revealed that citrus pectin displayed a uniform and dense pattern of point-like adsorption on the surface of calcite. Micro-flotation experiments showed that cassiterite recovery of 80% can be obtained at a citrus pectin dosage of 10 mg/L. Citrus pectin has the advantages of being low-cost, highly selective, and environmentally suitable, making it a promising alternative to conventional reagents.

Collectors commonly have synergetic effects in ores flotation. In this work, a waste engine oil (WEO) was introduced as a collector to an ilmenite flotation system with sodium oleate (NaOL). The results show that the floatability of ilmenite was significantly improved by using WEO and NaOL as a combined collector. The recovery of ilmenite was enhanced from 71.26% (only NaOL) to 93.89% (WEO/NaOL combined collector) at the pH of 6.72. The optimum molar ratio of NaOL to WEO was about 2.08 to 1. The WEO and NaOL also have synergetic effects for the collection of ilmenite, because to obtain the ilmenite recovery of 53.96%, the dosage of 45 mg/L NaOL is equal to 38.56 mg/L WEO/NaOL combined collector (30 mg/L NaOL + 8.56 mg/L WEO). In other words, 15 mg/L of NaOL can be replaced by 8.56 mg/L of WEO. It is an effective way to reduce the dosage of the collector and reuse WEO. Therefore, it is a highly valuable and environmentally friendly approach for WEO reuse. WEO mainly consists of oxygen functional groups, aromatics, and long-chain hydrocarbons, especially for the RCONH₂ and RCOOH, thereby forming a strong interaction on the ilmenite surface. The adsorption mechanism of waste engine oil and sodium oleate on the ilmenite surface is mainly contributed by chemical adsorption. Therefore, WEO exhibits superior synergistic power with NaOL as a combined collector. Herein, this work provided an effective collector for ilmenite flotation and a feasible approach for reducing NaOL dosage and recycling WEO.

A series of impact compression tests were conducted to study the breakage characteristics of magnetite, as well as the impact pressure on its strain rate and dynamic compressive strength. The dynamic mechanical properties and fragmentation size distribution of magnetite under diverse impact loads and cyclic impact were investigated, with fractal theory as a basis and split Hopkinson pressure bar (SHPB). Breakage methods were also employed to analyze the fracture morphology of magnetite. According to the result, the fractal dimension can reflect the distribution of fragments in various sizes. If the strain rate increases, the fractal dimension will be larger, the fragment size will be finer, and the fragmentation degree will be more influential. A micro-analysis of SEM images demonstrates that the fracture morphology is determined by mineral properties. Under low load cyclic impact, intergranular fracture is the main fractography. Besides, the intergranular fracture will be changed to a transgranular one as the impact load increases.

In this work, the active sites and species involved in xanthate adsorption on sphalerite/marmatite surfaces were studied using adsorption capacity measurements, single mineral flotation, and time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis. The effects of Fe concentration on the xanthate adsorption capacity, Cu activation, and the flotation response of sphalerite/marmatite were determined. A discovery was that xanthate can interact with Fe atoms in the crystal of sphalerite/marmatite, as well as with Zn and Cu on the surface. We detected C₂S₂⁻ fragment ions from dixanthogen, and dixanthogen may have been adsorbed on the surface of marmatite. The amounts of Cu and copper xanthate adsorbed on the marmatite surface were lower than those on the sphalerite surface, because Fe occupies Cu and Zn exchange sites. These results help to address the long-standing controversy regarding the products and mechanisms of xanthate adsorption on Fe-bearing sphalerite surfaces.