Renewable Collector Research Articles

Cottonseed oil biodiesel used as a renewable collector for coking coal flotation

ABSTRACT Hydrocarbon oil collectors used in coking coal flotation are nonrenewable resources, and their collecting performance is difficult to meet current industry needs. In this study, cottonseed oil biodiesel (CSOB) was prepared from cottonseed oil by alkali-catalyzed transesterification, and experimental studies on flotation of 1/3 coking coal were carried out. The results showed that the clean coal yield was about 75% when the use of CSOB was 2000 g t−1. The results of contact angle, FTIR and XPS tests showed that the oxygen-containing groups of CSOB were adsorbed on the hydrophilic spots on the surface of coal particles, and the surface hydrophobicity of coal particles was increased. The ash level of the clean coal with the addition of CSOB during flotation was essentially the same as with the addition of an equivalent amount of diesel oil.

Preparation of renewable collector from waste engine oil for clean flotation of fine coal with different oxidation degree

High precision flotation of fine oxidized coal is difficult to achieve because of very low floatability. In this study, the influence of oxidation degree on floatability and functional group composition of coal was studied. In addition, the feasibility of renewable collector prepared from waste engine oil for fine coal flotation was also analyzed. FTIR analysis results showed that the oxidation degree had no significant effect on the types of functional groups. However, XPS analysis results illustrated that with the deepening of oxidation degree, the content of CC/CH groups decreased significantly, which caused notable decrease in floatability. For the unoxidized coal, the clean coal yield and recovery rate were 62.51 % and 73.77 % respectively, which provided evidence support that renewable collector could be used for the flotation of fine coal. Moreover, with the deepening of oxidation, the yield and combustible recovery were finally reduced to 12.39 % and 14.09 % respectively due to oxidation of the particle surface. Thus, grinding pretreatment was proved to improve floatability of oxidized coal significantly. The yield of clean coal and combustible recovery reached 47.78 % and 52.93 %, which was mainly due to the fact that the oxide layer on the particle surface was stripped off by grinding. The research also proved that the flotation temperature should not be lower than 20 °C. The flotation of fine oxidized coal was realized by using waste engine oil, which brought an alternative collector for flotation on the premise of eliminating environmental threat of waste engine oil.

A novel renewable collector from waste fried oil and its application in coal combustion residuals decarbonization

A novel renewable collector was prepared by transesterification of waste fried oil (WFO), which was used to remove the unburned carbon in the coal combustion residuals (CCRs). The specific preparation process included purification, filtration, alkali catalysis, and oxidation (ozonization). Coal gasification ash (CGA) and coal fly ash (CFA) are the two main CCRs, and their properties were analyzed by XRD, SEM, FTIR and XPS. The results showed that most of CGA and CFA particles had rough surface and strongly hydrophilic surfaces owing to the existence of abundant oxygen-containing functional groups (35.93% and 66.95%, respectively). Waste fried oil collector (WFOC) was rich in oxygen-containing groups, which could be adsorbed onto carbonaceous matter surfaces to achieve hydrophobization. Ozonization could increase the content of oxygen-containing functional groups (CO, -C-O-C-, etc) in O3-WFOC. As the oxidation time increased, CGA and CFA had the same increasing trend of the flotation rate (fastly-slowly-fastly-slowly), and the better ozonization time was 2 h. This work demonstrated that WFOC/O3-WFOC could reduce the dependence on traditional collectors, cut down the flotation cost and solve the environmental problems caused by large amounts of CCRs and WFO by “waste control through waste”.

Resource utilization of waste oil in kitchen waste: preparation of renewable collector for cleaner flotation of high-sulfur fluorite ore

ABSTRACT Waste oils from kitchen waste pose a significant environmental threat. Meanwhile, desulfurization treatment of high-sulfur fluorite ore is also a challenge due to the harmfulness of sulfur. Thus, this study focuses on the preparation of collector from waste oil for the separation of high-sulfur fluorite ore in order to eliminate the environmental threat of the two waste. The flotation kinetic characteristics of pyrite with renewable collectors were studied and the kinetics analysis shows that the rapid flotation of pyrite with different grain sizes could be achieved. Thus, the pre-desulfurization process of high sulfur fluorite ore was proposed. Subsequently, the flotation efficiency of renewable collector on desulfurized fluorite ore was verified. The flotation results illustrate that 83.85% of sulfur can be removed with xanthate dosage of 60 g/t. Further, the sulfur content in the fluorite concentrate can be reduced to 0.02% with 91.52% fluorite recovery by single flotation test with 1.7 kg/t renewable collector dosage. Moreover, the closed-circuit flotation process was designed, fluorite concentrate with CaF2 grade of 97.08% can be obtained, and the sulfur content is only 0.04%. An innovative flotation process of high-sulfur fluorite using renewable collectors prepared from waste oils is proposed, which realized the high-value utilization of waste oils and high-sulfur fluorite.

Clean flotation of fine coal assisted by renewable collector prepared from waste oils

ABSTRACT Two innovative collectors, i.e. ionic collectors and microemulsion collector were prepared from waste oil to achieve clean flotation of fine coal by gradient flotation, which helps to reduce dependence on traditional nonrenewable collectors. Ionic collectors were prepared and used for the removal of gangue particles from fine coal. Further, the biodiesel prepared from waste oil was emulsified to improve the dispersibility, and microemulsion collector was used for deep purification of fine coal. The effect of microemulsion collector dosage on flotation kinetics was also analyzed. The flotation results show that the ionic collector can effectively remove the gangue particles. When the ionic collector dosage is 1500 g/t, the ash removal reaches 43.63% with 9.17% combustible loss. Zeta analysis shows that the negative electricity on the particle surface hindered the adsorption of gangue particles and collectors in the neutral environment. The flotation kinetics test results of microemulsion collector show that the flotation rate of particles increases with the increase of collector dosage. The first-order model adopted in this study has good fitting accuracy. This study provides an environmentally friendly flotation process for fine coal and realizes the utilization of waste oil.

Recycling metals from -0.5 mm waste printed circuit boards by flotation technology assisted by ionic renewable collector

Metals in −0.5 mm waste printed circuit boards (WPCBs) are effectively recycled by flotation technology. Ionic renewable collector was prepared from waste oils and subsequently used in flotation of −0.5 mm WPCBs. Morphology of renewable collector and WPCBs powder was detected by scanning electron microscope (SEM). Laboratory flotation tests were conducted to analyze the flotation performance. The adsorption behavior of the collector was revealed by infrared spectroscopy (FT-IR). SEM results show that the particle size of collector is in the micron scale and the impurity particles in WPCBs are in strip shape. Organic matter is proved to exist on the glass fibers surface, which helps to enhance its hydrophobicity. FT-IR analysis results indicate that both the collector and WPCBs powder contain hydrophobic and hydrophilic groups, which help to increase the attachment point of collector to strengthen the flotation process. Laboratory flotation test results show that the concentrate yield decreases with the increase of collector dosage. When the collector dosage is 2 kg/t, copper and iron grade in concentrate reaches 31.32% and 37.28% with the recovery of 65.75% and 14.55%, respectively. The study has provided an alternative method for the recycling of metals in WPCBs.

Metal recovery from waste printed circuit boards by flotation technology with non-ionic renewable collector

Using waste oil as renewable collector, flotation method was proposed to recover metal from waste printed circuit boards (WPCBs). The flotation mechanism was revealed by functional group composition, which was analyzed by infrared spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS). Elemental analysis shows that Cu and Fe in WPCBs are mainly concentrated in 1–0.5 mm and −0.5 mm respectively with ideal dissociation, which is verified by SEM + EDS analysis. Waste oil from kitchen waste was purified and used as flotation collector to realize the separation of metal particles and non-metal particles. The effect of collector dosage on the flotation behavior of 1–0.5 mm and −0.5 mm was analyzed respectively. Flotation results show that metal content in concentrate increases with the increase of collector dosage, which is accompanied by recovery decrease. For 1–0.5 mm, concentrate with 47.77% Cu and 91.15% recovery was obtained with 8 kg/t collector. For −0.5 mm, Fe and Cu content achieved 40.01% and 8.03% respectively, with recovery of 71.99% and 91.61% when the collector dosage was 1 kg/t. The functional group composition was determined by FT-IR and the carbon-based functional group content was tested by XPS, which illustrates the adsorption of the collector on the particle surface. The physical methods proposed in this study contribute to the cleanliness of the metal recovery process and realize the resource utilization of two kinds of waste.

Cleaner approach to fine coal flotation by renewable collectors prepared by waste oil transesterification

Abstract In order to realize the cleaner flotation production of fine coal, renewable collector was prepared by transesterification of waste oil in kitchen waste, which can be used as alternatives to traditional collectors. The functional groups and components of renewable collectors were analyzed by FT-IR and GC-MS respectively. Further, the flotation effect of the synthesized collector on fine coal was verified by laboratory flotation test, and the adsorption of the collector on the coal surface was analyzed by XPS. Results of FT-IR showed that the renewable collector contains the functional groups of –CH3, –CH2, C O, and C–O bonds. The GC-MS results showed that small molecules were produced through transesterification of crude oils, which proved that the carbon chain was interrupted. The adsorption analysis showed that the collector can be adsorbed effectively and enhance the particle hydrophobicity. In addition, the flotation experiment results showed that the fine coal could be effectively cleaned through the application of renewable collector, and the low temperature resistance of the collector has also been verified. The study proves that the renewable collector prepared by transesterification of waste oil can reduce the dependence on traditional collectors, which promotes the cleanness of fine coal flotation process.

Clean utilization of waste oil: Soap collectors prepared by alkaline hydrolysis for fluorite flotation

Abstract An innovative approach of clean utilization of waste oil is proposed to reduce the risk of environmental pollution and achieve cleaner production of fluorite. The waste oil in kitchen waste was first separated from solid waste and waste water. Further, alkaline hydrolysis was succeeded in preparing soap collectors by saponification reaction. Further, the fluorite flotation was conducted to verify the applicability of the renewable collectors. The results of FT-IR show that the characteristic peaks of the renewable collector appear on the particle surface after the adsorption treatment, which indicates that the collector can be effectively adsorbed. Effect of renewable collector on the charge properties of fluorite surface was analyzed and results show that the electronegativity of particle surface is enhanced after adsorption, which indicates that chemisorption can occur under alkaline conditions. The flotation test results show that the renewable collector has excellent separation effect on fluorite. The flotation kinetic analysis indicates that the four kinetic models have ideal applicability for describing the flotation behavior of renewable collectors for fluorite. The research results reveal the optimistic prospect of harmful waste oil transformation into collectors, and have potential industrial application prospects.

Gutter oil, an alternative collector to traditional diesel collector for cleaner flotation of fine coal

ABSTRACT In order to realize cleaner production of coal flotation and reduce the dependence of traditional nonrenewable diesel collector, renewable collector was prepared from gutter oil and used for the flotation process. For contrast, flotation performance of gutter oil and traditional diesel collector was analyzed. The functional group composition of the two collectors was compared by infrared spectrum analysis (FTIR). In addition, the adsorption properties of collectors on the particle surface were analyzed by X-ray photoelectron spectroscopy (XPS). Then, flotation experiments were conducted to verify the applicability of renewable collector. FTIR results show that the main functional groups of diesel oil are C-C and C-H, while the gutter oil contains C = O and C-O besides hydrophobic groups, which results in higher ash content of clean coal. XPS results show that the hydrophobicity group content of coal increased significantly after the adsorption of collector. The flotation result show that the ash content of clean coal can be reduced to less than 10% and accompanied by more than 80% combustible matter recovery for both the gutter oil and diesel oil. This study demonstrates that the coal flotation process can become cleaner by using gutter oil as green collector.

Recovery of high-grade copper from waste printed circuit boards by mechanical-grinding assisted flotation

Mechanical grinding combined flotation technology with renewable collector has been proposed to recover high-grade copper from waste printed circuit boards (WPCBs). Surface morphology and element distribution of copper particle section were analyzed using scanning electron microscopy and energy dispersive spectrometry (SEM + EDS) technology. Results show that the copper particle is covered with a layer of micrometer-scale organic matter. Thermogravimetric analysis demonstrates the organic layer commonly existed on all of the particle surfaces, which prove that the pyrolysis method was not feasible for selectively removing the organic impurity. Mechanical grinding pretreatment was proposed to peel off the organic layer. Grinding experiment results show that impurity can be effectively separated from copper. Soap collector prepared from waste oil was used for flotation. The flotation results show that the copper grade of the concentrate first increased and then decreased with the increase of the grinding time, while the recovery gradually decreased from 78.7% to 21.7%. Concentrate with 79.1% copper grade and 71.5% recovery was obtained when the grinding time was 3 min. This study provides a physical approach to recover high-grade copper from WPCBs.

Recovery of metals in waste printed circuit boards by flotation technology with soap collector prepared by waste oil through saponification

Recycling metal from waste printed circuit boards (WPCBs) through green flotation technology has been concerned in this paper. For the sake of environmentally friendly of flotation process, a renewable collector was prepared from waste oil by saponification reaction. The collector composition was analyzed by GC-MS, and results show that the main compositions are n-Hexadecanoic acid, oleic acid and octadecanoic acid. XRD and XRF results show that copper is the main valuable element for recovery. Effects of collector dosage and pH on flotation behavior were analyzed. In addition, the feasibility of improving copper recovery by multiple sorting test processes was also verified. Flotation results show that the concentrate yield and metal recovery decreases with the increase of collector dosage, accompanied by the increase of copper grade. When the dosage of collector is 3 kg/t, concentrate with 22% yield, 66% copper grade, and 47% copper recovery is obtained. Furthermore, concentrate yield and metal recovery rate first decrease and then increase with the increase of pH, while copper content first increase and then decrease. The suitable pH of the separation process is neutral environment (pH = 6–8). The study provides an alternative process for the recovery of metals in WPCBs.

Waste colza oil used as renewable collector for low rank coal flotation

The high cost of low rank coal flotation using diesel as the collector significantly restricts the improvement in economic efficiency of the coal plant. Waste colza oil (WCO) from the catering industry was used as a renewable and alternative collector for ultrafine low rank coal flotation in this investigation. Scanning electron microscopy (SEM) test was carried out to check the surface morphologies of the coal sample. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) tests were performed to examine the coal chemical compositions. The flotation yield using WCO was always higher than that of using diesel, especially at a high dosage. When 6 kg/t dosage was used, 35.68% yield was obtained with WCO, 5.54% higher than that with diesel. The mechanism of WCO used as an alternative collector was discussed based on the induction time, FTIR, and XPS tests. The induction time of the low rank coal after conditioning with 6 kg/t diesel and WCO were 200 ms and 100 ms, respectively, indicating that WCO was a more effective collector for improving the floatability of low rank coal compared with traditional diesel. XPS tests confirmed the adsorption of WCO on coal surface as the WCO has a large amount of CO groups according to FTIR results. The hydrogen bonding between oxygen-containing groups in WCO and low rank coal surface was responsible for the improvement of floatability and flotation recovery.

Reducing environmental threats of gutter oil: application in fluorite flotation by saponification

ABSTRACTIn order to reduce the environmental threat of kitchen waste, the gutter oil was transformed into renewable collector by saponification and used for flotation of fluorite. The adsorption characteristics of the collector on fluorite surface were analyzed by X-ray photoelectron spectroscopy (XPS). The influence of the collector dosage and inhibitor dosage on the separation efficiency was analyzed by the flotation test. XPS results show that collector can change the charge characteristics of calcium ions, indicating that the collector has significant adsorption on the fluorite surface. Separation results show that the renewable collector has achieved an excellent effect on fluorite flotation.

Biodiesel as a renewable collector for coal flotation in the future

ABSTRACTBiodiesel is a renewable and clean energy which is being developed day by day. However, oil and coal reserves are decreasing due to an increase in energy demand for the development of social economy. Additionally, fine coal is usually beneficiated by flotation using diesel or kerosene as collectors, which may be a waste of energy. Therefore, using biodiesel as a collector for coal flotation has its potential value. In this investigation, biodiesel was used as a collector for coal flotation. Three bituminous coal samples with different coal ranks were selected, that is, gas coal, coking coal, and lean coal. FTIR results showed that biodiesel contained much more abundant unsaturated fatty acids than diesel. Flotation results showed that the flotation performances of three coal samples using biodiesel as collector were similar to that using diesel as collector. Even better, the concentrate yields of three coal samples using biodiesel as collector were a little higher than that using diesel as collector, while their concentrate ash contents were similar. Throughout this paper, it was proved that biodiesel could have a potential application in coal flotation.