Runqing Liu

A review on in situ phytoremediation of mine tailings

Mine tailings are detrimental to natural plant growth due to their physicochemical characteristics, such as high pH, high salinity, low water retention capacity, high heavy metal concentrations, and deficiencies in soil organic matter and fertility. Thus, the remediation of mine tailings has become a key issue in environmental science and engineering. Phytoremediation, an in situ cost-effective technology, is emerging as the most promising remediation method for mine tailings by introducing tolerant plant species. It is particularly effective in dealing with large-area mine tailings with shallow contamination of organic, nutrient and metal pollutants. In this review, the background, concepts and applications of phytoremediation are comprehensively discussed. Furthermore, proper amendments used to improve the physical, chemical and biological properties of mine tailings are systematically reviewed and compared. Emphasis is placed on the types and characteristics of tolerant plants and their role in phytoremediation. Moreover, the role of microorganisms and their mechanism in phytoremediation are also discussed in-depth.

Flotation recovery of vanadium from low-grade stone coal

Abstract Pre-concentration of vanadium from low-grade stone coal by the method of desliming–flotation was investigated. The mineral composition and microstructure of stone coal were studied systematically by means of X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that selective separation of vanadium-bearing minerals can be achieved by flotation in acidic solution using melamine (EA). The final vanadium concentrate with V2O5 grade of 1.88% and recovery rate of 76.58% is obtained by desliming–flotation process and 72.51% of the raw ore is rejected as tailings. The pre-concentration of vanadium from low-grade stone coal can increase V2O5 grade and decrease the content of acid consuming minerals, which would enable economical utilization of metallurgical vanadium extraction technology.

Surface chemical study of the selective separation of chalcopyrite and marmatite

FCLS (Ferric Chromium Lignin Sulfonate) was used to aid the separation of chalcopyrite from marmatite. Flotation, adsorption and zeta-potential tests of treated marmatite and chalcopyrite were performed. The flotation of marmatite was strongly depressed, while that of chalcopyrite was only slightly depressed, over a wide range of pH values when FCLS was used as depressant in the presence of Butyl Xanthate (BX). The adsorption of BX onto chalcopyrite or marmatite takes place over a wide pH range. The adsorption density of BX on chalcopyrite and marmatite decreases as the pH increases. The adsorption density of FCLS onto marmatite is greater than the adsorption density onto chalcopyrite. The zeta potentials of chalcopyrite and marmatite become more negative due to the addition of xanthate and FCLS.

The utilization of waste by-products for removing silicate from mineral processing wastewater via chemical precipitation

This study investigates an environmentally friendly technology that utilizes waste by-products (waste acid and waste alkali liquids) to treat mineral processing wastewater. Chemical precipitation is used to remove silicate from scheelite (CaWO4) cleaning flotation wastewater and the waste by-products are used as a substitute for calcium chloride (CaCl2). A series of laboratory experiments is conducted to explain the removal of silicate and the characterization and formation mechanism of calcium silicate. The results show that silicate removal reaches 90% when the Ca:Si molar ratio exceeds 1.0. The X-ray diffraction (XRD) results confirm the characterization and formation of calcium silicate. The pH is the key factor for silicate removal, and the formation of polysilicic acid with a reduction of pH can effectively improve the silicate removal and reduce the usage of calcium. The economic analysis shows that the treatment costs with waste acid (0.63

Electrochemical behavior of galena and jamesonite flotation in high alkaline pulp

/m3) and waste alkali (1.54

pH effects on adsorption behavior and self-aggregation of dodecylamine at muscovite/aqueous interfaces

/m3) are lower than that of calcium chloride (2.38

Synergistic mechanism between SDBS and oleic acid in anionic flotation of rhodochrosite

/m3). The efficient removal of silicate is confirmed by industrial testing at a plant. The results show that silicate removal reaches 85% in the recycled water from tailings dam.

Efficient utilisation of flue gas desulfurization gypsum as a potential material for fluoride removal

In order to effectively separate galena and jamesonite and improve the recovery during the mixing flotation, the interaction mechanisms between the minerals and the collector of diethyl dithiocarbamate (DDTC) were investigated. Single mineral flotation test was organized to research the effect of pulp pH value on the flotation behavior of galena and jamesonite. Electrochemistry property of the interaction of these two minerals with DDTC was investigated by cyclic voltammetry and Tafel tests. Flotation test shows that the recovery of jamesonite in high alkaline pulp is strongly depressed by lime (Ca(OH)2). The cyclic voltammetry and Tafel tests results show that the interaction between galena and DDTC is an electrochemical process. High pH value has little influence on the interaction between galena and DDTC, while it has great effect on jamesonite due to self-oxidation and specific adsorption of OH− and CaOH+ on jamesonite surface. Non-electroactive hydroxyl compound and low-electroconductive calcium compounds cover the surface of jamesonite, which impedes electron transfer and DDTC adsorption, thus leads to very low floatability of jamesonite.

Selective depression mechanism of ferric chromium lignin sulfonate for chalcopyrite–galena flotation separation

In this work, molecular dynamics simulation was used to examine the effect of solution pH on the adsorption behavior and self-aggregation of dodecylamine hydrochloride (DDA) on the muscovite (0 0 1) surface. The properties of surfactants are assessed in terms of density profiles in the direction perpendicular to the muscovite surface. Results show that although DDA can adsorb at muscovite at all pH we discussed, the self-aggregation of DDA varies significantly at different pH values. At pH 10, a compact hydrophobic monolayer forms on the muscovite surface. At pH 3, hemi-micelle aggregated structure forms with several DDA cations far away from muscovite surface. At pH 12, it has been confirmed that adsorption of DDA neutral molecules occurs with only a few DDA molecules adsorbing on muscovite directly and acting as a bridge linking the rest DDA molecules, which exists nearby muscovite surface irregularly. Density profiles revealed that at pH 10, DDA cations play a dominant role in the interaction between DDA surfactants and muscovite. While DDA molecules have difficulty in forming a hydrogen bond with the oxygen atom on the muscovite surfaces, and they co-adsorb onto muscovite through the electrostatic interactions with muscovite and hydrophobic force with DDA cations. Therefore, the hydrophobization of muscovite in the presence of DDA are higher at pH 10 than that at pH 3 and pH 12. Our results indicate that molecular dynamics simulation can be a power tool in charactering adsorption behavior of surfactants onto mineral surfaces at different pH values.

An extensive review on restoration technologies for mining tailings

Pure mineral flotation experiments, zeta potential testing, and infrared spectroscopy were employed to investigate the interfacial reactions of oleic acid (collector), sodium dodecyl benzene sulfonate (SDBS, synergist), and rhodochrosite in an anionic system. The pure mineral test shows that oleic acid has a strong ability to collect products on rhodochrosite. Under neutral to moderately alkaline conditions, low temperature (e.g., 10°C) adversely affects the flotation performance of oleic acid; the addition of SDBS significantly improves the dispersion and solubility of oleic acid, enhancing its collecting ability and flotation recovery. The zeta potential test shows that rhodochrosite interacts with oleic acid and SDBS, resulting in a more negative zeta potential and the co-adsorption of the collector and synergist at the mineral surface. Infrared spectroscopy demonstrated that when oleic acid and SDBS are used as a mixed collector, oleates along with –COO– and –COOH functional groups are formed on the mineral surface, indicating chemical adsorption on rhodochrosite. The results demonstrate that oleic acid and SDBS co-adsorb chemically on the surface of rhodochrosite, thereby improving the flotation performance of the collector.