Comparative Study of the Effect of Frothers on the Flotation of Nickel Sulphide Ore

Froth flotation process is an important process that involves solid-solid/solid-liquid separation of minerals from gangue. However, the performance of froth separation is affected by the types of frothers. The purpose of this study, therefore, was to determine the effect of different frothers in the flotation of low-grade nickel sulphide obtained in South Africa. Sodium isobutyl xanthate was used as a collector in this investigation. The mineralogy analysis showed that the samples of the ores contained 0.33 and 2.45% nickel feed grade for ore samples A and B, respectively. Batch flotation tests were performed on the ore samples using two different frothers namely Senfroth XP 200 and 516. Some of the nickel was found to be associated with the gangue minerals present in these ores and recoveries were based on the total nickel value. It was observed that 0.24 and 0.29% of the total 0.333% of the feed ore were recovered from sample A by Senfroth XP 516 and 200, respectively. The results also revealed that 1.77 and 2.13% of the total 2.45% of the feed ore were recovered from sample B by 516 and XP 200, respectively. Analysis of the results revealed that 0.07 and 0.04% of the nickel were recovered from the tailing by Senfroth XP 516 and 200, respectively from the ores grade sample A, while 0.53 and 0.30% of nickel were recovered from the tailing of sample B. It can be deduced from this work that Senfroth XP 516 is more selective for the recovery of nickel from nickel sulphide ore as compared to the Senfroth XP 200. The better performance of Senfroth XP 516 can be attributed to the better adsorption capacity and level of interaction of the Senfroth 516 and the dispersant employed in this study.     

Heavy metal removal from waste waters by ion flotation

Flotation studies were carried out to investigate the removal of heavy metals such as copper (II), zinc (II), chromium (III) and silver (I) from waste waters. Various parameters such as pH, collector and frother concentrations and airflow rate were tested to determine the optimum flotation conditions. Sodium dodecyl sulfate and hexadecyltrimethyl ammonium bromide were used as collectors. Ethanol and methyl isobutyl carbinol (MIBC) were used as frothers. Metal removal reached about 74% under optimum conditions at low pH. At basic pH it became as high as 90%, probably due to the contribution from the flotation of metal precipitates.     

The kinetics modeling of chalcopyrite and pyrite,and the contribution of particle size and sodium metabisulfite to the flotation of copper complex ores

In this study, a series of batch flotation experiments was conducted to evaluate both the role of particle size distribution and the presence of sodium metabisulfite Na₂S₂O₅ (SMBS) in chalcopyrite and pyrite flotation. Kinetic flotation tests were also carried out in order to evaluate the kinetics behavior of the above-mentioned minerals. Following this, different flotation kinetics models were compared to the data from the experiments. According to the obtained results, it can be stated that feed particle size distribution plays a greater role in chalcopyrite and pyrite grades rather than their recoveries. However, the contribution of SMBS is higher than that of particle size with respect to pyrite recovery. In this study, the maximum recoveries for chalcopyrite and pyrite were found to be 92.2% and 47.5%, respectively. The minimum pyrite recovery (13.47%) occurred in the presence of 40 g/t Xanthate-flomin (C-4132), 20 g/t methyl isobutyl carbonyl (MIBC), 20 g/t polypropylene glycol (F742), 200 g/t sodium metabisulfite (SMBS), and at a d ₇₀ of 70 µm. A comparison between several flotation kinetics models and the experimental data revealed that the perfect mixer and the Arbiter models showed completely similar results for both chalcopyrite and pyrite with respect to the use of different configuration of chemical reagents.     

Removal of Congo red from aqueous solution by adsorption onto different amine compounds modified sugarcane bagasse

Different amine compounds, including ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine, modified sugarcane bagasse (SCB) were prepared to improve its adsorption capacity for anionic dye Congo red. Batch studies were carried out to investigate the effect of various parameters including surface nitrogen content, the amine compounds chain length, contact time, initial concentration, solution pH and salt on the adsorption of Congo red. Results showed that the adsorption capacity of the sorbents did not increase consistently with the increase in the surface nitrogen content, and it varies in the order: unmodified < ethylenediamine-modified < diethylenetriamine-modified ≈ triethylenetetramine-modified ≈ tetraethylenepentamine-modified sugarcane bagasse. The diethylenetriamine-modified sorbent had similar capacity with the triethylenetetramine- and tetraethylenepentamine-modified sorbent. The adsorption mechanism based on electrostatic attraction and steric hindrance was proposed. pH and salt experiment illustrated that the prepared sorbents could be used in a wide pH range (5.0–12.0) and a high-salinity environment (1.0 mol L^?1). Dynamic adsorption of Congo red on tetraethylenepentamine-modified SCB fixed-bed column showed that breakthrough time and saturated time were 364 and 1109 min, respectively. The modified SCB could be regenerated efficiently and used repeatedly. It had great potential in the real wastewater treatment.     

The effect of selective adsorption of dissolved aegirite species on the separation of specularite and aegirite

The separation of specularite from aegirite is challenging due to the similar floatability. Surface dissolution of minerals often occurs and affects their physicochemical properties. In order to investigate the effect of dissolved aegirite species on the separation of specularite and aegirite, the separation performance of these two minerals was explored through surface pretreatment before froth flotation. The adsorption mechanism was investigated via Zeta potential measurements, scanning electron microscope (SEM) tests, and X-ray photoelectron spectroscopy (XPS) analyses. Single mineral flotation experiments indicated that acidified pretreatment significantly reduced the floatability of aegirite (from 78.4% to 15.1%) and specularite (from 88.7% to 38.4%) at pH 10 with 6 × 10^-5 mol/L dodecylamine. The alkalified pretreatment only affected the flotation of aegirite (from 78.4% to 16.3%) at pH 10, while specularite maintained its floatability (85.4%). Mixed mineral flotation results confirmed that specularite was depressed while aegirite recovered its floatability with alkalified pretreatment. Zeta potential measurements and SEM analyses indicated that surface element dissolution occurred on the pretreated mineral surface, which increased the positive electrical property of minerals and weakened the adsorption of the dodecylamine. XPS results further revealed that the Si and Fe dissolved from the alkalified aegirite surface formed SiO₃^2-, Fe(OH)₃, and FeOOH at the specularite surface, which depressed the flotation of specularite.     

Synthesis,Characterization, and Cesium Sorption Performance of Potassium Nickel Hexacyanoferrate-Loaded Granular Activated Carbon

GAC has been modified by loading of potassium nickel hexacyanoferrate (KNiCF) as a new adsorbent for cesium adsorption. The potassium nickel hexacyanoferrate-loaded granular activated carbon (KNiCF-GAC) was characterized using powder x-ray diffraction (XRD) and nitrogen adsorption-desorption isotherm data, infrared spectroscopy, and its cesium adsorption performance in aqueous solution was investigated. The effect of the various parameters such as initial pH value of the solution, contact time, temperature, and initial concentration of the cesium ion on the adsorption efficiencies of KNiCF-GAC have been studied systematically by batch experiments. The adsorption isotherm of KNiCF-GAC was studied and the fitted results indicated that the Langmuir model could well represent the adsorption process. The maximum adsorption capacity of Cs⁺ onto KNiCF-GAC was found to be 163.9 mg · g^?1.     

Carbon dioxide adsorption using amine-functionalized mesocellular siliceous foams

Mesocellular siliceous foams (MCFs) with and without remaining template were prepared and modified by polyethylenimine (PEI) or mixed amines [Diethylenetriamine and PEI or 3-aminopropyltrimethoxysilane (APTMS) and PEI]. These samples were evaluated for their adsorption capacities for CO₂ at different temperatures. With the increase of PEI loading, the optimal adsorption temperature shifts to higher temperature for samples prepared in our study. The remaining template in MCF materials plays an important role in promoting CO₂ adsorption capacity, which could be 3.24 mmol/g when the amount of PEI loading is 70 % at 85 °C. Meanwhile, the remaining template contributes greatly to the dispersion of PEI, resulting in higher adsorption capacity at low temperature. The effect of the amount of remaining template was studied, and it was found that CO₂ adsorption capacity decreases with increasing template. The CO₂ adsorption capacities for mixed-amine-modified MCFs are higher than those of the samples modified by PEI only, which was ascribed to the better dispersion of PEI. MCF modified with the mixing of APTMS and PEI exhibited highest adsorption capacity of 2.67 mmol/g at 50 °C. These findings reveal that pore structure, PEI loading, PEI dispersion, and remaining template work together to influence the CO₂ adsorption performance.     

Efficient desulfurization of fuel with functionalized mesoporous carbon CMK-3-O and comparison its performance with mesoporous carbon CMK-3

In this work, a functionalized mesoporous carbon (CMK-3-O) was synthesized after oxidation with nitric acid and was used to adsorb dibenzothiophene (DBT) from model oil for the first time. Then, its performance was compared with that of CMK-3. The functionalized mesoporous carbon, CMK-3-O, showed better a capacitance performance for DBT adsorption than that of CMK-3. The maximum adsorption capacity was obtained for functionalized mesoporous carbon at optimum conditions with 6 M HNO₃ aqueous solution and 30 min contact time. The physical and structural properties of CMK-3-O and CMK-3 were investigated with X-ray diffraction method (XRD), N₂ adsorption–desorption isotherm, FT-IR, and elemental analysis (CHNO). Results of the elemental analysis showed that the oxygen and nitrogen content has increased and the carbon content has decreased through oxidation treatment. The effects of various factors on the adsorption process (such as temperature, amount of adsorbent, contact time, and concentration) of DBT were studied. CMK-3-O showed a maximum adsorption capacity of 86.96 mg DBT g^?1 of CMK-3-O at optimized conditions (temperature, 25°C; adsorbent dosage, 20 g L^?1; contact time, 60 min), which was a higher adsorption capacity of that observed for CMK-3 (57.47 mg DBT g^?1 of CMK-3). Kinetic studies have revealed that the adsorption of DBT can be described by a pseudo-second-order rate equation. Equilibrium data showed that adsorption process was best represented by the Langmuir model. The results also illustrated the fact that the regenerated adsorbent afforded 64.3% of the initial adsorption capacity after the two regeneration cycles.     

Preparation of a Low-Cost Adsorption Material from Red Mud and Bagasse

Preparation of bagasse carbon-red mud (BCRM), a low-cost adsorption material used in wastewater treatment, from red mud and bagasse has been studied. Effects of most important conditions in preparation process on the adsorption capability of BCRM were investigated. The optimal preparation parameters for BCRM were obtained. BCRM had a high surface area and a good mesoporous structure and exhibited an excellent adsorption capacity. The used BCRM could be regenerated via simple calcination at 573 K in air for 1 h. BCRM was an effective, economic, and regenerable material for adsorption of organic contaminants in wastewater.     

Separation of fines by flotation techniques

A large amount of valuable minerals is discarded today as fines and ultrafines because of inadequate technology to process them economically. Treatment of fine particles presents a difficult problem in the chemical industry and raw materials processing, and its solution is required both in production and effluent treatment. This article reviews various suitable flotation techniques—such as precipitate flotation, flocculation-flotation, column flotation, dissolved-air flotation, and electrolytic flotation and presents different laboratory experiments with fines (mostly at the subsieve size range) as examples. Also included is the conventional froth flotation and particularly the effect of bubbles size on performance. Although froth flotation is a commonly applied selective separation process in mineral processing, it becomes inefficient for beneficiating fines. In the closing overview of the process, several ideas for future research are suggested.     

Synthesis of water-compatible surface-imprinted composite microspheres with core–shell structure for selective recognition of thymopentin from aqueous solution

A novel water-compatible surface-imprinted core–shell microsphere, which had multiple non–covalent interactions with template molecule, was successfully prepared by the surface grafting polymerization method in acetonitrile–water systems with thymopentin as template through ionic liquid-functionalized polyethyleneglycolmethacrylate-co-vinylimidazole microsphere as the matrix. The average diameter of matrix was 1 μm ± 20 nm and the thickness of imprinted layer was about 50 nm. The results of static adsorption experiments indicated that ionic liquid-functionalized molecularly imprinted microspheres showed the good adsorption capacity and specific recognition for template peptide. The binding-isotherm analysis showed that Langmuir isotherm models gave a good fit in the range of concentrations, suggesting that there was only one kind of binding site in imprinted layer. Measurements of the binding kinetics revealed that surface-imprinted composite microspheres reached peptide-adsorption equilibrium in 60 min and the maximum adsorption capacity for TP5 was 38.4 mg g^?1. The effects of pH, salt concentration, and temperature on the adsorption capacities were investigated. The microspheres were found to have a high specificity for TP5 with little affinity for BSA and Hb. Finally, the core–shell microspheres can be reused with only 15.6 % decrease in TP5 adsorption capacity after six times.     

Separation of polyvinyl chloride (PVC) from automobile shredder residue (ASR) by froth flotation with ozonation

The purpose of this study is to develop froth flotation to separate polyvinyl chloride (PVC) from automobile shredder residue (ASR) plastic mixtures of variable composition. Some polymers in ASR polymer mixtures have similar density and hydrophobicity with PVC and thus selective flotation of PVC from ASR polymer mixtures cannot be achieved. The present study focused on the surface modification of PVC with ozonation, and then the modified PVC can be separated from other polymers by the following froth flotation. The results of this study indicate that the selective recovery of PVC from real ASR polyethylene tetra pethelate (PET), polymethyl methacrylate (PMMA), polybutyl methacralate (PBMA), ethyl acrylate (EA), polycarbonate (PC) and rubber mixtures can be accomplished in a three-step process involving a gravity separation, ozonation and froth flotation. The rubber was removed from other heavy ASR (PVC, PET, PMMA, PBMA, EA and PC) polymers by froth flotation without mixing. It was found that ozonation process produced the desired difference in contact angle required (from 89.5 to 73.0 degrees ) for separation of PVC from other heavy ASR polymers, whereas the contact angles of other polymers was slightly decreased. The most of the load ASR, i.e. about 72.4% is floated away and 27.6% was settled down. The highest component 96.7% of PVC was recovered in the settled fraction. As a result of this research effort, the surface modification of PVC with ozonation can be efficiently useful to separate the PVC from other similar density ASR mixed polymers.     

Adsorption of a lignosulphonate polymer onto PVC and PET surfaces: Evaluation by XPS

As part of the separation by froth flotation of PVC and PET from waste bottles before recycling, the adsorption mechanism of a lignosulphonate used to selectively render one of the plastics hydrophilic has been studied. As the 'rest' method is not sufficiently sensitive for this purpose, X-ray Photoelectron Spectroscopy analysis was conducted. A method of calculating the surface coverage of both plastics by the reagent is proposed based on the fact that the lignosulphonate contains sulphur whereas PVC and PET do not. The results show that a greater quantity of lignosulphonate adsorbs on PET than PVC, leading to a higher surface coverage of LS on PET. The surface coverage values are a function of the lignosulphonate macromolecular configuration. For the sphere and film configurations hypothetised, the surface coverage values remain less than 1, which is consistent with the patchy adsorption assumed in the calculations.     

Experimental and modelling studies of carbon dioxide adsorption by porous biomass derived activated carbon

The goal of the study was to produce a low-cost activated carbon from agricultural residues via single stage carbon dioxide (CO₂) activation and to investigate its applicability in capturing CO₂ flue gas. The performance of the activated carbon was characterized in terms of the chemical composition, surface morphology as well as textural characteristics. The adsorption capacity was investigated at three temperatures of 25, 50 and 100 °C for different types of adsorbate, such as purified carbon dioxide and binary mixture of carbon dioxide and nitrogen. The purified CO₂ adsorption study showed that the greatest adsorption capacity of the optimized activated carbon of 1.79 mmol g^?1 was obtained at the lowest operating temperature. In addition, the adsorption study proved that the adsorption capacity for binary mixtures was lower due to the reduction in partial pressure. The experimental values of the purified CO₂ adsorption were modelled by the Lagergren pseudo-first-order model, pseudo-second-order model, and intra-particle diffusion model. Based on the analysis, it inferred that the adsorption of CO₂ followed the pseudo-second-order model with regression coefficient value higher than 0.995. In addition, the adsorption study was governed by both film diffusion and intra-particle diffusion. The activation energy that was lesser than 25 kJ mol^?1 implied that physical adsorption (physisorption) occurred.     

Investigation of cationic starch/Na-montmorillonite bionanocomposite adsorbent prepared by vibration milling for acid dye removal

In this study, the low-cost powder bionanocomposite based on cationic starch (CS) and Na-montmorillonite (MMT) was obtained by the one-step procedure in a homemade vibration mill. The analysis of the bionanocomposite by x-ray diffraction (XRD) and thermogravimetric analysis (TGA) methods revealed that MMT had intercalated structure in CS matrix and the bionanocomposite possessed enhanced thermal stability as compared with that of pure CS. Adsorption capacity of CS/MMT bionanocomposite toward Acid Scarlet dye was evaluated as a function of initial dye concentration and contact time. The adsorption tests showed that the adsorption kinetics followed the pseudo-second order chemisorptions kinetic model. The adsorptions isotherms were best fitted using the three-parameter Sips model with the maximum adsorption capacity of 43.7 mg/g for CS/MMT bionanocomposite against 13.4 mg/g for CS.     

High surface area ordered mesoporous carbon for high-level removal of rhodamine B

We report the synthesis of ordered mesoporous carbons (OMCs) with high surface area by the variation of mass ratio of tetraethylorthosilicate (TEOS) to resol, followed by carbonization and removal of silica. The obtained OMCs were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N₂ adsorption and desorption analysis, Zeta potential and Fourier transform infrared spectroscopy. Results reveal that the OMCs were transformed from ordered to disordered structure at high mass ratio of TEOS/resol. A typical sample of OMCs possesses very high specific surface area of 1906 m² g^?1 and large pore volume of 1.8 cm³ g^?1. The OMCs as adsorbent show an ultrahigh-level adsorption capacity for the removal of toxic dye Rhodamine B (1028 mg g^?1) in the short contact time (60 min). The adsorption follows pseudo second-order kinetics with rate constant 2.5 × 10^?4 g mg^?1 min^?1, showing rapid adsorption properties. The OMCs can be reused; though the adsorption capacity seems to decrease somewhat after each cycle tested over 10 reuse cycles, it might be affected by the chemisorptions. The adsorption mechanism study reveals that the adsorption proceeds with hydrogen bonding between hydrogen atom of carboxylic group at OMCs and electronegative element (nitrogen) of RhB. It is concluded that the surface area and pore volume of the OMCs is tuned by the variation of mass ratio of TEOS to resol which is also demonstrated to have ultrahigh adsorption capacity for the model RhB dye.     

Adsorption kinetics, isotherm, and thermodynamics of Hg2+ to polyaniline/hexagonal mesoporous silica nanocomposite in water/wastewater

A nanocomposite of polyaniline/hexagonal mesoporous silica (PAN/HMS) was prepared and characterized by BET analysis, transmission electron microscopy, and FT-IR spectra. Batch adsorption results showed that PAN/HMS had high affinity to Hg²⁺ in aqueous solutions. Various factors affecting the adsorption capacity such as contact time, temperature, absorbent dosage, pH, and initial concentration of Hg²⁺ ions were investigated. The adsorption kinetics for the Hg²⁺ showed that the adsorption reached equilibrium within 8 min and adsorption rates followed the pseudo-second-order rate law, indicating chemical sorption as the rate-limiting step of the adsorption mechanism. Sorption of Hg²⁺ to PAN/HMS agreed well to the Langmuir adsorption model at different ionic strengths with the maximum adsorption capacity of 843 mg g^?1 (I = 1000 mg L^?1) at pH 10. Thermodynamic studies revealed that the adsorption of Hg²⁺ ions was spontaneous, exothermic processes with an increase of entropy. The recovery of the Hg²⁺ from the adsorbent was found to be more than 88 % using H₂SO₄ (0.1 M), and the ability of the absorbent to be reused was investigated.     

An investigation into the effect of water quality on froth stability

Froth stability plays a major role in determining the mineral grade and recovery in flotation operations, and it depends on the type and amount of both frother and suspended particles. Furthermore, there are other parameters such as quality of the process water which may affect the froth stability. In plant practice, the recycling of process water instead of using fresh water is increasingly being common. However, using recycled water normally leads to building up salts and surfactants in solution. Therefore, the effect of the process water chemistry on froth stability and metallurgical performance is important. In this study, the effect of water quality, including pH, and type and concentration of salts (CaCl₂, AlCl₃ and NaCl) on froth stability and its relationship with mineral particles zeta potential and slurry viscosity was studied. It was found that the forth stability is higher in the presence of multivalent metal ions. Addition of CaCl₂ and AlCl₃ considerably increased both froth stability and pulp viscosity. This may be due to bridging effect of polyvalent metal ions between the ore particles.     

Effect of acid and hydrothermal treatments on the dye adsorption properties of biomass-derived activated carbon

Different types of acid pretreatment are known to influence the removal of certain components from pine wood sawdust, due to differences in the acid hydrolysis, which also predetermine the final formation and adsorptive properties of the produced activated carbon (AC) through subsequent potassium hydroxide activation. AC made by using phosphorous acid as an acid pretreatment had the largest absorption capacity of methylene blue (MB) dye due to its highest acidity. Subsequently, the effects on the adsorption variables for this AC such as initial pH, MB concentration, contact time and temperature were investigated. The resulting adsorption process was classified as pseudo-second-order kinetic model, and the Langmuir isotherm model better described the equilibrium data in comparison with the Freundlich isotherm model. The outcome showed that a lower temperature had an increased adsorption capacity of sawdust-derived AC pretreated with phosphorous acid, which allowed maximum adsorption capacities of 303.03 mg/g at 30 °C, implying that the adsorption was an endothermic process. Phosphorous acid pretreatment and activation processes proved to be an effective strategy to prepare highly porous AC from sawdust, with high potential to cationic dye removal from liquid phases.     

Synthesis of polypyrrole/Fe-kanemite nanocomposite through in situ polymerization: effect of iron exchange,acid treatment,and CO<Subscript>2</Subscript> adsorption properties

This paper focuses on the synthesis of polypyrrole/Fe-kanemite nanocomposites by in situ polymerization of pyrrole. Different percentages of PPy/Fe-kan have been prepared and tested for the CO₂ adsorption. Fe-exchanged kanemite was prepared using various iron contents and used as an oxidant for the preparation of PPy/Fe-kan nanocomposite. The obtained materials were characterized using various techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy, ultraviolet–visible (UV–vis), thermogravimetric analysis TGA, energy dispersive X-ray analysis, scanning and transmission electronic microscopy (SEM, TEM). Based on the XRD and UV–vis analysis, the exchange process leads to the formation of various iron species on the external and internal surface. The thermal stability of PPy/Fe-kan was improved and increased in the following order PPy/Fe-kan (1%) > PPy/Fe-kan (3%) > PPy/Fe-kan (5%) > PPy/Fe-kan (10%) > PPy. SEM and TEM analysis show that the nanocomposite particles have spherical morphology with a high dispersion of the Fe-kanemite in the polymer matrix. CO₂ adsorption at 0 and 15 °C was carried using a volumetric method, and the recorded isotherm indicated that the CO₂ adsorption capacity of PPy/Fe-kan can be enhanced through modification by polypyrrole. The unmodified Na-kanemite has low CO₂ adsorption capacity around 0.05 mmol g^?1 at 15 °C, while the PPy/Fe-kan (5%) nanocomposite presented the best CO₂ adsorption capacity around 1.7 mmol g^?1 at 0 °C under low pressure that is mainly attributable to physical adsorption.