EXPERIMENTAL RESEARCH AND APPLICATION OF COPPER OXIDE FLOTATION USING THE COMBINED COLLECTORS OF BENZOHYDROXAMIC ACID AND BUTYL XANTHATE

Daixiong Chen1,2, Jun Xiao 1,2,Chunming He1,2, Xiaodong Li 1,2

(1. Hunan Research Institute for Non-ferrous Metals; 2. Hunan Provincial Key Laboratory for Complex Copper Lead Zinc Associated Metal Resources Comprehensive Utilization.)

ABSTRACT

Benzohydroxamic acid with double dentate can combine with copper and form cyclic hydroxyl oxime acid copper chelate, so it has good recovering capability and selectivity for copper oxide minerals, especially for malachite. The flotation results of the pure mineral malachite show that the strongest synergistic collecting effect between hydroximic acid and xanthate can be generated with the highest malachite recovery of 95.5% when certain sodium sulphide is used as vulcanizing agent in the optimal pH range and the best ratio of hydroximic acid to xanthate is 3.5:1. In the refractory real ore flotation experiments, due to the synergistic collecting effect, the flotation recovery of malachite can reach to over 92% under the condition of optimum proportion, increasing 12% compared with the conventional collectors. In industrial production, the flotation indexes of the copper grade are high, and the copper oxide resource is utilized with high efficiency.

INTRODUCTION

Beneficiation of copper oxide ore is one of the recognized puzzles in mineral processing industry, and it is also the important research field for dressing workers. Copper oxide ore is the vital component of copper resource in the world, which has abundant reserves. Majority of sulphide deposits have oxidized zone on the top, and some oxidation deposits are oxidized to become the large and medium-sized oxidation deposits [1]. However, most copper oxide ores have the problems such as high slime, poor floatability, complex ore property and low flotation recovery, so it is of great significance in beneficiation of copper oxide ore to develop an efficient collector for copper oxide ore especially for malachite[2~4]. At present, sulfuration-xanthate flotation is the most important method for treating copper oxide ore. In recent years, due to the decrease of mining grade, the utilization of refractory copper oxide ore draws more and more attention [5], except for sulfuration-xanthate method, chelating flotation method [6], chemical beneficiation method [7], microwave irradiation flotation method, hydrothermal sulfuration-floatation method [8] and ammonia leaching of sulfide precipitation-floatation method [9] have been occurred.

1 MATERIAL PREPARATION OF SINGLE MINERAL FLOTATION EXPERIMENTS, REAGENTS AND RESEARCH METHODS

The pure malachite samples were taken from a mine in Congo, and the purity was 98%. It was peacock green with well crystallization, and the copper content was 54.8%. The samples were crushed, handpicked, ground in porcelain mill and then sieved with a 0.074mm sieve, the through product was used in experiments.

Reagents used in this reseach are as follows: sodium sulfide (Na2S·9H2O), analytically pure, colorless cubic crystal, soluble in water; butyl xanthate (C4H9OCSSNa), industrial quality, pungent pale yellow powder; benzohydroxamic acid (C7H7NO2), industrial quality with 70% purity, pink powder.

Single mineral flotation tests were conducted on a XFG-76 flotation machine with 50 ml volume, and the impeller speed was 1500 rpm. For each test, 2g of samples and moderate distilled water were added in the cell, and stirred 2 min to adjust the pulp, in order to examine the flotation behavior of malachite under different conditions. The flotation time was 3 min, after flotation, the froth product and the unfloated product were dried under natural conditions and weighed, and the percentage of the froth product weight to the total weight was calculated, that is the recovery, the experiment process is shown in Fig.1.

Fig. 1 The process of the pure malachite mineral flotation experiments

2 RESULTS AND DISCUSSIONS

2.1 CONDITION EXPERIMENTS OF SODIUM SULFIDE CONCENTRATION

The concentration of butyl xanthate and pine oil was fixed at 220mg/L and 72mg/L, respectively. The relationship between sodium sulfide concentration and malachite recovery is shown in Fig.2.

Fig.2 The relationship between sodium sulfide concentration and malachite recovery

The results showed that the recovery of malachite was extramely low when butyl xanthate was used as the collector without sodium sulfide. When sodium sulfide was used as vulcanizing agent and its concentration was in the range of 0~300mg/L, malachite recovery increased with the increase of sodium sulfide concentration, while the recovery had a decrease as the concentration was more than 300 mg/L.

Sodium sulfide, as a vulcanizing agent, can vulcanize malachite surface, mainly because sodium sulphide solution shows strong alkaline, adding sodium sulphide solution means adding OH-, HS- and S2- in the pulp, these three ions can react with malachite according to the following reactions:

In the case of the presence of OH- ions, part of mineral surface can achieve hydroxylation, the HS- ions change the hydroxylation area into sulfide area, at the same time part of the carbonate dissolves, leading to the formation of new hydroxylation area[4].The reaction will not stay on the mineral surface, but go deep into the mineral internal, and form the CuS thin films with different thickness, finally strengthened the hydrophobicity of mineral surface, and improved the adsorption rate of collector. At last, depending on the different initial concentrations of the sodium sulfide, CuS thin films of different thickness were formed[6].

The uneven surface of malachite made its surface exist different areas of complete sulfidation, incomplete sulfidation and non sulfuration, when butyl xanthate was used as the collector, it can adsorb on the complete sulfidation area of malachite surface, so some malachite can be recovered.

2.2 CONDITION EXPERIMENTS OF BUTYL XANTHATE CONCENTRATION

The concentration of sodium sulfide and pine oil was fixed at 300mg/L and 72mg/L, respectively. Butyl xanthate was used as the collector, and the relationship between its concentration and malachite recovery is shown in Fig.3.

Fig.3 The relationship between butyl xanthate concentration and malachite recovery

After the sulfuration of malachite, the area of complete sulfuration can be considered as copper sufide ore, in the redox system formed by the CuS thin film, dissolved oxygen and butyl xanthate, the dissolved oxygen took place reduction reaction in the cathode, and the oxidation reaction between CuS and butyl xanthate took place in the anode. Due to the two independent and interdependent electrode reaction processes of CuS thin film on malachite surface, xanthate can adsorb on CuS film successfully, and xanthate copper was formed, making malachite surface Hydrophobic, and the specific reaction process equation are as follows:

Because of the different surface activities of malachite surface, the optimal sodium sulfide concentrate for the formation of sulfide film is different, at the best concentration of sodium sulfide, only part of malachite surface formed complete sulfuration area, malachite of incomplete sulfuration area and non sulfuration area is difficult to adsorb butyl xanthate, at the same time, the adsorption of butyl xanthate on sulfide film of malachite surface was dynamic adsorption -desorption process, so it is difficult to achieve the complete recovery of malachite using single butyl xanthate.

Owing to the adsorption characteristics of butyl xanthate on malachite surface, the recovery of malachite increased with the increase of butyl xanthate concentration, when the concentration was more than 120 mg/L, the malachite recovery was basically constant, which was only 76.8% at the concentration of 160 mg/L.

2.3 Condition experiments of benzohydroxamic acid concentration

The concentration of pine oil was 72 mg/L, benzohydroxamic acid was used as the collector without sulfuration, and the effect of benzohydroxamic acid concentration on malachite recovery is shown in Fig.4.

Fig.4 The effect of benzohydroxamic acid concentration on malachite recovery

The results showed that part of malachite can be recovered using benzohydroxamic acid as the collector without sulfuration, mainly because benzohydroxamic acid can occur chemical adsorption on malachite surface, the bidentate on the one side can chelate with Cu2+ and form stable penta cyclic chelate, and the hydrocarbon chain on the other side was hydrophobic, thus making malachite floated, the main chemical equation is as follows:

Since the activity of copper ions on malachite surface is different, only part copper ions can form stable chelate with benzohydroxamic acid, so the malachite can not be recovered completely even if the concentration of benzohydroxamic acid has a great increase.

2.5 CONDITION EXPERIMENTS OF DIFFERENT RATIOS OF BENZOHYDROXAMIC ACID TO BUTYL XANTHATE

The concentration of sodium sulfide and pine oil was 300 mg/L and 72 mg/L, respectively. Benzohydroxamic acid and butyl xanthate were used as the combined collector, and the total concentration was 180 mg/L, the effect of the ratio of benzohydroxamic acid to butyl xanthate on malachite recovery is shown in Fig.5.

Fig.5 The effect of the ratio of...