Deep Insight on the Occurrence Feature of Iron Minerals in a Cyanide Leaching Residue and Its Effective Recovery with Magnetic Separation

Abstract

The occurrence features of ultrafine iron minerals in a cyanide leaching residue produced from a superlarge gold mining company in Yunnan Province were determined with chemical composition analysis, iron phase analysis, and mineral liberation analysis (MLA). The results show that the residue contains 26.74% iron, mainly occurring in the form of magnetite (26.33%) and limonite (69.41%), in which 67.40% magnetite and 73.00% limonite particles are fully liberated with particle sizes ranging from 9.6 µm to 75.0 µm. The rest are adjacent and wrapped intergrowths. Low-intensity magnetic separation and pulsating high-gradient magnetic separation were, respectively, proposed to recover magnetite and limonite from the residue, and under the optimized conditions, a high-grade magnetite concentrate assaying 64.05% Fe with 85.59% magnetite recovery and a qualified limonite concentrate assaying 50.94% Fe with 54.33% limonite recovery were, respectively, produced. The iron recovery for −30 µm fraction in the magnetite and limonite concentrates reached as high as 51.46%. It was found that the iron recovery for −30µm ultrafine fraction is lower than those of coarser fractions, as a result of the relatively enhanced hydrodynamic drag acting onto the particles, compared with the magnetic force. Entrainment occurs between the ultrafine iron minerals and gangues, thereby reducing the iron grade for the ultrafine fraction. This research outcome would provide a valuable reference for the economic and effective utilization of iron resources from such residues.

1. Introduction

Cyanide leaching residues produced from the gold mining industry in China are one of the main hazardous wastes, which occupy many lands and generate potentially serious impacts on local environments [1,2,3]. Generally, valuable iron minerals are found in significant amounts in such residues, but their enrichment and recovery are still economically unviable and with low efficiency, due to their ultrafine distributions in the residues [4,5]. This outcome mainly results from the requirement for ultrafine grinding of gold ores, to improve the gold and silver leaching efficiency with total-slime cyanidation technology. Another situation encountered in the exploration of gold ores lies in the fact that a certain portion of gold particles are associated with magnetite and limonite minerals, in which the limonite grains are sensitive to the grinding process and, therefore, are very easy to be lost into tailings [6,7].

In the past decade, the recovery of iron values from various tailings and leaching residues has become stringent, as the demand for iron materials has been steadily growing. For instance, a reduced roasting-sulfuric acid leaching process was proposed to recover ultrafine iron and gold minerals from a cyanide leaching residue, which contained 29.55% iron and 5.60 g/t gold, and a leaching ratio of 91.26% for iron and 71.43% for gold was, respectively, achieved under the optimized conditions [8]. Additionally, a heating leaching process with sulfuric acid was also attempted to recover hematite from a cyanide leaching residue and produced an iron leaching ratio reaching as high as 93.33% [9]. Another technical route of roasting–magnetic separation was proposed to process a cyanide leaching residue, in which hematite is the main iron mineral, and a magnetite concentrate assaying 61.78% iron grade with 60.67% iron recovery was produced [10]. A similar process was used to recover iron from a high-sulfur cyanide tailing; under strong reduction conditions, a reduced iron product with 90.68% Fe and 92.71% iron recovery was obtained [11]. Liu et al. proposed a process of chlorination roasting–carbothermic reduction–magnetic separation for the treatment of an Au-bearing cyanide residue and produced an iron concentrate containing 82.17% Fe, with a total Fe recovery of 79.68% [1]. These processes containing leaching or roasting operations are effective for iron extraction from low grade tailings and residues, but they are complex and include metallurgy treatment such that they become inevitably involved with high energy consumption and low economic viability. In fact, until today, few industrial applications of these processes were reported. Therefore, the effective enrichment of iron minerals prior to metallurgy is commonly required for removing the large amounts of gangue minerals in the residue, due to the technological and economic constraints of direct metallurgy.

Pulsating high-gradient magnetic separation (PHGMS) is one of the most effective methods for enrichment and recovery of ultrafine and weakly magnetic iron minerals, mainly due to its advantages of large processing capacity, low operation cost, high applicability, and environmental friendliness over other separation methods [2,12,13]. Particularly in recent years, superlarge SLon-5000 PHGMS separators with sufficiently high background magnetic induction were successfully developed, and their operating power consumption for per ton ore reached as low as 0.15 kWh. Moreover, the water used in the PHGMS process may be totally reused through gravity settling process, and therefore, it provides strong possibilities for economically and greenly recovering ultrafine iron values from tailings and leaching residues [14].

In this paper, an attempt was made to evaluate the feasibility of iron recovery from a cyanide leaching residue, which was produced from a superlarge gold mining company in Yunnan Province, using magnetic separation. Detailedly, the occurrence features of iron minerals in the residue were determined by chemical composition analysis, iron phase analysis, and mineral liberation analysis (MLA). Based on these analyses, a technological route of low-intensity magnetic separation (LIMS) and PHGMS was proposed, and the effects of their key operating parameters on the separation performance were elucidated for enrichment and recovery of ultrafine magnetite and limonite from the residue, respectively. Moreover, the magnetic capture of iron minerals was investigated using the size-by-size and chemical analyses of the iron concentrates. The results would provide important technological support for the comprehensive utilization of the residue in industry, increasing the economic and environmental benefits for the company.

2. Experimental

2.1. Description of Cyanide Leaching Residue

The cyanide leaching residue was obtained from the Heqing Beiya Mining Co., Ltd., Dali, China. For this investigation, the residue was naturally air-dried and then gently broken up into powders using a roller. The chemical compositions and iron phase analyses with a deviation less than 0.10% were conducted for the residues, and the results are illustrated in

Table 1. Chemical compositions of residue (* g/t).

Elements	TFe	Au *	SiO2	CaO	MgO	Mn	Cu	Pb	Zn	S	P
Contents/%	26.74	0.13	18.74	13.68	3.61	1.15	0.29	0.66	0.15	0.48	0.08

and

Table 2. Iron phase analysis of residue.

Iron Minerals	Magnetite	Limonite	Siderite	Ferro-Silicate	Sulfide	Total
Iron grades (%)	7.04	18.56	0.12	0.54	0.48	26.74
Iron distributions (%)	26.33	69.41	0.44	2.02	1.80	100.00

, respectively. Table 1 shows that the residue contains 26.74% iron, which is mainly distributed in magnetite and limonite particles, as shown in Table 2. The iron grades of magnetite and limonite in the residue are, respectively, 7.04% and 18.56%, with their iron distributions relative to total iron reaching 26.33% and 69.41%, respectively. The non-magnetic gangues in the residue are mainly composed of quartz, carbonate dolomite, calcite, and a small amount of feldspar and biotite. It is worth noting that the Cu, Pb, and Zn elements with very low grades are mainly dispersed in iron and manganese oxides, coronadite, and sphalerite, respectively; they are defined as unrecoverable minerals using current separation techniques.

The residue sample was classified into several fractions using a series of sieves (+20 μm) and elutriation methods (−20 μm), and the iron grades in each fraction were determined by a chemical method, as shown in

Table 3. Size-by-size analysis for iron distributions in residue.

Size Fractions (μm)	Weights (%)	Iron Grades (%)	Iron Distributions (%)
+74	9.96	17.79	6.63
−74~+45	13.17	32.23	15.87
−45~+30	16.43	30.98	19.04
−30~+20	22.30	30.49	25.43
−20~+10	14.32	24.31	13.02
−10	23.82	22.47	20.02
Total	100.00	26.74	100.00

. It shows that the weight and iron distribution for −30 μm fractions are 60.44% and 58.47%, respectively, indicating that the residue is seriously muddied, and most iron minerals occur as ultrafine grains. This is attributed to the use of the total-slime cyanide leaching method, for gold and silver in the upstream process.

2.2. Liberation Analysis of Magnetite and Limonite in Residue

Approximately 30,000 particles in the residue were automatically observed and counted to representatively reflect the liberation characteristics of target minerals, i.e., magnetite and limonite in the residue through a Mineral Liberation Analysis method (MLA650, FEI Company, Hillsboro, OR, USA). Based on this analysis, an appropriate separation technology for the recovery of ultrafine magnetite and limonite from the residue was determined.

2.3. Descriptions for Magnetic Separations

A wet drum LIMS separator (Φ 400 × 600, Wuhan Prospecting Machinery Factory, Wuhan, China) was used for the recovery of magnetite from the residue; in this separator, the highest magnetic induction of 0.35 T is achievable on the drum surface. When this magnetic separator was being operated, a direct current flow was generated through the energizing coils, resulting in a magnetic field on the drum surface. Firstly, the separating zone of the separator was filled with fresh water. Then, a slurry containing 500 g residue at 25% solid weight was evenly fed into the separator within 60 s. Magnetite particles were attracted from the slurry onto the drum surface and transferred to the concentrate flushing zone by the rotating drum, while weakly magnetic and non-magnetic particles exited from the separating zone to become tailings. The lifted magnetite particles were flushed down by flushing beams to obtain a magnetite concentrate.

The tailings produced from the above LIMS process were further separated through a cyclic pilot-scale PHGMS separator (SLon-100, SLon Magnetic Separator Ltd., Ganzhou, China) to recover limonite particles. This separator has a maximum background magnetic induction of 1.8 T, and for this investigation, a rod matrix was adopted. The separation principle and operation procedure of this separator were described previously [15,16].

The produced magnetite and limonite concentrates were filtered, dried, and weighed, with their iron grades determined by chemical analysis. The theoretical iron recovery in the concentrates was calculated by Formula (1).

$$\epsilon =\frac{\gamma \times \beta }{\alpha }\times 100\%$$

(1)

where ε (%) is the iron recovery, γ (%) is the weight of the concentrate, and α (%) and β (%) are the iron grades of residue and concentrate, respectively.

3. Results and Discussion

3.1. Occurrence Features of Iron Minerals in Residue

3.1.1. Liberation Characteristics of Magnetite and Limonite

Based on the MLA analysis of the residue, the liberation characteristics and quantified liberation analysis of magnetite or limonite were determined, which are shown in Figure 1 and Table 1, respectively. It should be noted that the liberation degree is defined as the volume ratio of targeted iron mineral grains in a particle, while the liberation proportions describe the proportion of targeted iron mineral particles with a liberation degree to the totally observed particles that contain magnetite or limonite. The cumulative proportions were calculated by Formula (2).

$$\Gamma =\Sigma {\theta }_i$$

(2)

where Γ and θ_i are the cumulative proportion and individual proportion of liberated minerals, respectively, and i = 1, 2, 3, 4, or 5.

It can be seen from Figure 1 that there are complex mineral compositions and liberation characteristics in the residue, which results in the difficulty of enrichment for iron minerals. From

Table 4. Liberation degree analysis of magnetite and limonite in residue.

Iron Minerals	Liberation Degrees (%)	Proportions (%)	Cumulative Proportions (%)
Magnetite	100%	67.40	67.40
	75% < x < 100%	19.22	86.62
	50% < x ≤ 75%	5.16	91.78
	25% < x ≤ 50%	4.58	96.36
	0% ≤ x ≤ 25%	3.64	100.00
Limonite	100%	73.00	73.00
	75% < x < 100%	17.79	90.79
	50% < x ≤ 75%	4.61	95.40
	25% < x ≤ 50%	2.66	98.06
	0% ≤ x ≤ 25%	1.94	100.00

, it can be derived that the residue had a proportion of full liberation particles, reaching 67.40% for magnetite and 73.00% for limonite, respectively. The proportions for below half liberation degree were 8.22% for magnetite and 4.60% for limonite, respectively. These results again demonstrate that most iron minerals occurred as ultrafine grains in the residue, resulting in negative effects on the recovery of ultrafine iron mineral particles from the residue.

The microscopic parageneses of magnetite and limonite with gangues are shown in Figure 2. The incompletely liberated limonite particles were mainly associated with dolomite, andradite, quartz, etc. in the forms such as limonite coating on quartz, and they were finely wrapped in kaolinite; meanwhile, the incompletely liberated magnetite particles were adjacently associated with quartz and biotite, as shown in Figure 2.

In summary, the distribution characteristics of limonite and magnetite in the residue may be divided into three categories—namely, individual particles, adjacent intergrowth, and wrap intergrowth particles. The individual limonite and magnetite particles are relatively easy for magnetic separation. However, the main consideration should be given to the adjacent and wrap iron intergrowths, because they would lead to the harmful elements entering the iron concentrates, and also reduce the iron grade of concentrates.

3.1.2. Particle Size Distributions of Magnetite and Limonite

Based on the MLA analysis above, the particle size distribution of magnetite and limonite in the residue was studied, which is shown in Figure 3. It shows that the cumulative distributions of limonite above 75 μm, 38 μm, 19 μm, and 9.6 μm size ranges were 12.09%, 46.57%, 73.18%, and 90.01%, respectively, while the cumulative distributions of magnetite above 75 μm, 38 μm, 19 μm, and 9.6 μm size ranges were 8.60%, 49.05%, 81.33%, and 95.16%, respectively. These results confirm that the magnetite and limonite minerals mainly occurred as fine and ultrafine particles in the residue, which is unamiable for iron recovery during magnetic separations.

Based on the occurrence features of iron minerals in the residue, a low-intensity magnetic separation (LIMS)-pulsating high-gradient magnetic separation (PHGMS) process was proposed for the effective recovery of iron minerals from the residue.

3.2. Magnetite Recovery with LIMS Process

Magnetic induction is a key factor that affects the enrichment of strongly magnetic minerals when a wet drum magnetic separator is used. The effect of magnetic induction on the LIMS roughing performance is shown in Figure 4a. The iron grade of roughing concentrate decreased, while the iron recovery steadily increased with increasing magnetic induction. This is attributed to the fact that more intergrowth particles including magnetite and other minerals (Figure 2) enter the roughing concentrate at high magnetic inductions. Although the lowest iron grade of 57.32% was obtained, the magnetic induction of 0.35 T was proposed for the roughing process at the highest recovery of 26.65%. This roughing magnetite concentrate should be further cleaned to produce a qualified magnetite concentrate with an iron grade higher than 60%.

It can be seen from Figure 4b that the iron grade of magnetite concentrate slightly decreased and the iron recovery observably increased when the magnetic induction increased from 0.10 to 0.15 T during the cleaning process. In the magnetic induction range of 0.15–0.30 T, the iron grade obviously decreased, but the iron recovery increasingly approached the maximum. These results suggest that the satisfactory separation performance was achievable if only the magnetic condition was not lower than 0.15 T. Under such a magnetic induction, a qualified magnetite concentrate assaying 64.18% Fe at 22.85% iron recovery was produced from the residue, as clearly shown in Figure 4b.

3.3. Limonite Recovery with PHGMS Process

PHGMS tests were attempted to recover limonite from the tailings produced in the LIMS roughing process. The iron phase analysis showed that the tailings contained 22.69% Fe, and the iron dominantly existed in the form of limonite at a 93.41% ratio of total iron. In this part, the effects of background magnetic induction, wire diameter of rod matrix, and pulsating frequency on the PHGMS roughing performance were firstly investigated, followed by a cleaning process to produce a qualified limonite concentrate.

3.3.1. Effect of Magnetic Induction on Roughing Separation Performance

The effect of magnetic induction on roughing separation performance is shown in Figure 5. It shows that magnetic induction had a very significant influence on the performance of the PHGMS roughing process. The iron recovery of concentrate increased with increasing magnetic induction, while the other variables remained constant. In addition, the iron grade of the concentrate slowly decreased with an increase in magnetic induction from 0.6 T to 1.2 T, and this decrease sharply enhanced when the magnetic induction reached higher than 1.2 T. Thus, the magnetic induction of 1.2 T is favorable for both grade and recovery of the concentrate. Under this condition, a roughing limonite concentrate assaying 45.48% Fe at 47.52% iron recovery was obtained.

3.3.2. Effect of Magnetic Wire Diameter on Roughing Separation Performance

The PHGMS roughing separation performance with different wire diameters of the rod matrix is shown in Figure 6. When the rod wire diameter was changed from 1.5 mm to 3.0 mm, the iron grade of roughing limonite concentrate obviously increased. Although the 3.0 mm rod matrix achieved the highest iron grade, the 2.0 mm rod matrix is more desirable due to its superior capacity for the capture of ultrafine limonite particles from the residue. In addition, it has higher reliability in practice, compared with the finer 1.5 mm rod matrix, although it has a relatively lower selectivity than that of the 1.5 mm rod matrix.

3.3.3. Effect of Pulsating Frequency on Roughing Separation Performance

One essential feature in the PHGMS technology is the pulsation of slurry in the separating matrix. Therefore, in this study, the effect of pulsating frequency on the PHGMS roughing performance was investigated, with results shown in Figure 7.

It can be seen that the concentrate grade significantly increased, while the recovery inappreciably decreased with increasing pulsating frequency from 0 to 300 rpm. However, both the grade and recovery of the concentrate obviously decreased with a further increase in the frequency to 350 rpm. This observation is explainable by the pulsating effect in the PHGMS process as follows: The pulsating energy in the matrix is enhanced with increasing pulsating frequency; thus, the particles in the slurry are subjected to increasingly strong hydrodynamic drag against the magnetic force, which results in the high selectivity for the rejection of mineral particles with relatively low liberation degree, iron content, and magnetic susceptibility. As a result, the concentrate grade is improved, and the iron recovery is softly decreased in the primary limonite concentrate when the pulsating frequency lies in the suitable range. The concentrate grade and iron recovery then considerably decrease as the frequency is excessive, which is attributed to the fact that the mineral particles with relatively high liberation degree and iron content begin to be washed out from the matrix [15,16].

In this PHGMS roughing process, a primary limonite concentrate assaying 46.54% Fe with 47.45% iron recovery was produced at a pulsating frequency of 300 rpm, while the other variables remained constant, i.e., magnetic induction of 1.2 T and a flow rate of 6.0 cm/s.

3.3.4. PHGMS Cleaning for Primary Limonite Concentrate

The primary limonite concentrate produced from the PHGMS roughing process under the optimum conditions—namely, 1.2 T magnetic induction, 300 rpm pulsating frequency, 2.0 mm matrix, and 6.0 cm/s flow rate—was further separated through the PHGMS cleaning process in order to obtain a qualified limonite concentrate with an iron grade higher than 50%. It was found that the magnetic induction and pulsating frequency had dominant controls on the iron grade and recovery of limonite concentrate, as observed in the PHGMS roughing process above. The improvement in the concentrate grade was approximately in the range of 3–5% in this PHGMS cleaning process.

With the operating parameters, optimized as 0.8 T magnetic induction, 250 rpm pulsating frequency, 2.0 mm matrix, and 4.0 cm/s flow rate in the PHGMS cleaning process, a qualified limonite concentrate assaying 50.36% Fe with the recovery of 42.66% was produced from the residue, as illustrated in

Table 5. PHGMS cleaning separation results in recovery of limonite from residue.

Products	Mass Weight (%)	Iron Grades (%)	Iron Recoveries (%)
Limonite concentrate	22.65	50.36	42.66
Tailings	4.61	27.77	4.79
Feed	27.26	46.54	47.45

. It is clear that this PHGMS cleaning process is effective for removing low-grade intergrowths and entrains slimes and gangues from the primary limonite concentrate at a small loss of 4.61% weight and 4.79% iron recovery.

3.4. LIMS–PHGMS Process Test and Products Analysis

In the present study, a whole test for the LIMS–PHGMS process was carried out using the above optimized operating conditions, as illustrated in Figure 8.

The concentrate products produced from this magnetic separation process were determined based on chemical analysis, with the results summarized in

Table 6. Separation results of LIMS–PHGMS process for residue.

Products	Weights (%)	Iron Grades (%)			Iron Recoveries (%)
		Total	Magnetite	Limonite	Total	Magnetite	Limonite
Magnetite concentrate	9.65	64.05	62.44	1.28	23.11	85.59	0.67
Limonite concentrate	21.97	50.94	4.53	45.90	41.85	14.14	54.33
Tailings	68.38	13.70	0.03	12.21	35.04	0.27	45.00
Feed	100.00	26.74	7.04	18.56	100.00	100.00	100.00

. It is clear that, under the optimized conditions, the magnetic separation process produced a high-grade magnetite concentrate assaying 64.05% Fe with 85.59% magnetite recovery, and a qualified limonite concentrate assaying 50.94% Fe with 54.33% limonite recovery from the residue.

These magnetite and limonite concentrates were size-by-size analyzed, to obtain a deep understanding of the magnetic capture to different particle size magnetites in the LIMS process, and limonites in the PHGMS process. Additionally, the iron recoveries for fractions in the residue and the iron recoveries for the fractions were calculated using Formulas (3) and (4), respectively. As can be inferred from

Table 7. Size-by-size analysis of magnetite and limonite concentrates.

Products	Size Fractions (µm)	Weights (%)	Iron Grades (%)	Iron Recoveries (%)
				For Fractions	For Residue
Magnetite concentrate	+74	0.52	59.02	17.33	1.15
	−74~+45	1.92	62.16	28.09	4.46
	−45~+30	2.54	66.39	33.14	6.31
	−30~+20	3.28	65.43	31.58	8.03
	−20~+10	0.91	62.24	16.27	2.12
	−10	0.48	58.65	5.24	1.05
	Total	9.65	64.05	/	23.11
Limonite concentrate	+74	1.43	48.90	39.41	2.61
	−74~+45	5.04	50.44	59.94	9.52
	−45~+30	5.50	52.70	56.94	10.84
	−30~+20	5.15	52.44	39.72	10.10
	−20~+10	2.19	49.68	31.23	4.07
	−10	2.66	47.48	23.60	4.72
	Total	21.97	50.94	/	41.85

, the iron grades and fraction recoveries for +74 µm and −74 + 45 µm fractions in the magnetite concentrate were both lower than those for −45 + 30 µm and −30 + 20 µm fractions, as a result of the relatively lower liberation degree and magnetism of the coarser particles. The iron grades and fraction recoveries for −20 µm + 10 µm and −10 µm fractions significantly decreased, as a result of the reduced magnetic attraction for ultrafine iron minerals. For the limonite concentrate, the iron grades and recoveries of fractions decreased with a decrease in the particle size of 0–74µm, indicating an increased difficulty for recovery of iron minerals of finer particle size, and the entrainment occurring of ultrafine gangues.

$${\epsilon }_c=\frac{{\gamma }_c\times {\beta }_c}{\alpha }\times 100\%$$

(3)

$${\epsilon }_f=\frac{{\epsilon }_c}{\mu }\times 100\%$$

(4)

where ε_c is the fraction iron recoveries for the residue, γ_c is the fraction weight in the concentrate, β_c is the fraction iron grade in the concentrate, α is the iron grade of the residue, ε_f is the fraction iron recoveries, and μ is the iron distribution of the fraction in the residue from Table 3.

The detailed chemical compositions and iron phase analysis of the magnetite and limonite concentrates are, respectively, illustrated in

Table 8. Chemical compositions for magnetite and limonite concentrates (* g/t).

Concentrates	TFe	Au *	SiO2	CaO	MgO	MnO	Cu	Pb	Zn	S
Magnetite (%)	64.05	0.23	2.61	1.03	0.18	0.62	0.13	0.29	0.07	0.14
Limonite (%)	50.94	0.11	6.89	3.05	0.64	2.63	0.20	1.03	0.23	0.28

and

Table 9. Iron phase analysis for magnetite and limonite concentrates.

Concentrates	Iron Minerals	Magnetite	Limonite	Siderite	Ferrosilicate	Sulfide	Total
Magnetite	Iron grades (%)	62.44	1.28	0.09	0.12	0.12	64.05
	Iron distributions (%)	97.49	2.00	0.14	0.19	0.19	100
Limonite	Iron grades (%)	4.53	45.90	0.10	0.16	0.25	50.94
	Iron distributions (%)	8.89	90.11	0.20	0.31	0.49	100

. The results clearly show that the magnetite concentrate contained 64.05% Fe with 97.49% iron distributed in magnetite form, whereas the limonite concentrate contained 50.94% iron with 90.11% iron distributed in limonite form. The main impurities in the magnetite and limonite concentrates were SiO₂, at 2.61% and 6.89%, respectively; the Cu, Pb, Zn, and S mainly recovered in the limonite concentrate. This is due to the fact that some limonites are adjacently intergrown with gangue minerals such as coronadite and sphalerite, which reduces the concentrate grade.

4. Conclusions

The cyanide leaching residue contained 26.74% Fe, with iron mainly distributed in the forms of magnetite and limonite. The iron grades from magnetite and limonite in the residue were 7.04% Fe and 18.56%, respectively, reaching 26.33% and 69.41%, respectively, of the total iron. The residue had a proportion of full liberation particles reaching 67.40% for magnetite and 73.00% for limonite, respectively, with particle sizes ranging from 9.6 µm to 75.0 µm. The gangue minerals in the residue were mainly carbonated dolomite and calcite, with a small amount of quartz, feldspar, biotite, and clay minerals.

With a LIMS roughing (0.30 T)–cleaning (0.15 T) process under the optimum conditions, a magnetite concentrate assaying 64.05% Fe at 9.65% mass weight and 23.11% iron recovery was produced from the residue, with magnetite recovery reaching as high as 85.59%. From the tailings of this LIMS process, a qualified limonite concentrate assaying 50.94% Fe at 21.97% mass weight and 41.85% iron recovery was produced through a PHGMS roughing (1.2 T)–cleaning (0.8 T) process under the optimized conditions, with limonite recovery, reaching 54.33%. This LIMS–PHGMS process reached an effective recovery for ultrafine (below 30.00 µm) iron minerals from the residue, which is quantified as 51.46% fraction recovery in the magnetite and limonite concentrates. This research work provides a valuable reference for the comprehensive utilization of iron values from such residues.