Study on the Effect of Grinding Media Material and Proportion on the Cyanide Gold Extraction Process

Abstract

Laboratory and industrial tests were conducted to study the impact of grinding media material on key indicators such as grinding product particle size, sodium cyanide consumption, gold recovery rate, unit power consumption, and ball consumption. Laboratory test results indicate that the reasonable mixing of ceramic and steel balls can achieve an increase of more than 2.8% in the fineness of the grinding product (−0.038 mm), an increase of 0.3% in the gold recovery rate, and a decrease of 1.3 kg/t in the consumption of sodium cyanide. Industrial trial studies indicate that, compared to the traditional steel ball scheme, using a ceramic ball to steel ball mass ratio of 3:1 under conditions of processing 50,000 tons of gold concentrate annually can save a total of 1.31 million yuan in annual ball consumption, electricity consumption, and cyanide consumption costs. Additionally, the improved recovery rate generates an additional economic benefit of 3.63 million yuan, resulting in an annual comprehensive economic benefit increase of 4.94 million yuan. In summary, in gold cyanide leaching grinding, the mixture ratio between ceramic balls and steel balls demonstrates significant potential for energy conservation, cost reduction, and efficiency enhancement, providing a theoretical basis and technical support for subsequent process optimization and green gold extraction.

1. Introduction

Gold, as an important precious metal mineral resource, has widespread applications in the global economy and industrial sectors [1]. Cyanidation is one of the primary processes for gold extraction; however, the high consumption of sodium cyanide in this process not only increases production costs but also poses potential environmental risks [2]. In order to further improve cyanidation efficiency and reduce the amount of cyanide used, gold cyanidation during the grinding process was developed. This process is a gold extraction process that combines grinding and leaching. Its principle involves adding a cyanide solution during the grinding process, enabling gold in the ore to be dissolved by the cyanide while grinding, thereby improving the gold leaching rate.

In the grinding process, the selection and ratio of grinding media have a critical impact on the subsequent cyanidation process. Currently, steel grinding media remains dominant, primarily comprising two categories: high-chromium steel and low-chromium steel [3]. However, regardless of whether high-chromium steel or low-chromium steel is used, iron losses inevitably occur during grinding. These iron ions react with sodium cyanide, significantly increasing sodium cyanide consumption. More importantly, iron ions tend to accumulate gradually in the cyanidation system, thereby affecting the physical and chemical properties of the slurry and inhibiting the effective leaching of gold [4,5]. Feng and van Deventer [6] found that adding metallic iron or trivalent iron (Fe³⁺) during wet grinding significantly reduces gold leaching rates and efficiency; metallic iron causes greater interference than Fe³⁺ at equivalent concentrations. Additionally, the presence of iron species accelerates the decomposition of thiosulfate, forming colloidal iron oxides that deposit on sulfide mineral surfaces, further hindering gold leaching activity. Cui et al. [7] found that the presence of Fe²⁺ in cyanide solutions significantly consumes sodium cyanide while reducing the gold leaching rate. The introduction of Fe²⁺ causes a substantial increase in sodium cyanide consumption, resulting in an approximately 28% reduction in leaching rate. Different types of iron minerals have varying effects on cyanide leaching, with sulfide iron minerals (such as FeS₂ in the ore) having a particularly pronounced impact on gold leaching.

Ceramic grinding media have the advantages of good chemical stability, high hardness, wear resistance, and corrosion resistance [8]. Previous studies have shown that when using hard stones or ceramic balls as grinding media, the iron ion content in the grinding product is lower, which is beneficial for the flotation recovery of copper minerals [9,10]. Although the study focused on copper minerals, it can be inferred that in the grinding process of gold cyanide leaching, the mixed addition of ceramic balls and steel balls may also reduce the enrichment of iron ions on the mineral surface. This is because ceramic balls are less likely to introduce iron ions during grinding compared to steel balls, thereby reducing interference with the surface properties of minerals and facilitating subsequent cyanide leaching processes. In industrial trials at the Shizhuyuan Concentrator in Hunan Province, Liao et al. [11] replaced steel cylindrical media with ceramic balls. After replacement, the content of the −10 μm particle size fraction in the grinding product decreased, while the content of the intermediate −74 + 10 μm particle size fraction increased. Concurrently, power consumption decreased by 38.5%, and grinding media consumption decreased by 60%. Jing and Xu [12] used ceramic balls to replace steel balls as grinding media in slag grinding at the Guixi Smelter. This effectively reduced grinding media consumption, lowered grinding power consumption per ton, and saved grinding costs. According to calculations, partially replacing steel balls with ceramic balls can reduce grinding power consumption per ton of slag by approximately 3 kW·h/t. However, due to the lower density of ceramic media (approximately 3.7 g/cm³), which is significantly lower than that of steel media (7.5–7.8 g/cm³), the mass of ceramic media per unit volume is much smaller than that of steel media under the same filling rate. This results in weaker kinetic energy transfer, insufficient impact force, and significantly lower grinding capacity compared to steel media. This can lead to inadequate mineral liberation and failure to achieve the desired grinding fineness requirements [13,14]. Yin et al. [14] analyzed the effect of different density media (3.8, 5.8, and 7.8 g/cm³) on collision energy loss through discrete element simulation and experimental analysis. The results showed that the total collision energy of the medium with a density of 3.8 g/cm³ (such as ceramic balls) was significantly lower than that of the medium with a density of 7.8 g/cm³, indicating that low-density media release less energy during grinding and have relatively weaker grinding capabilities.

Steel media and ceramic media exhibit distinct characteristics during grinding processes. In industrial applications, relying solely on either type of grinding media fails to adequately address the dual requirements of grinding efficiency and operational stability. Therefore, this paper innovatively proposes the idea of mixing ceramic media and steel media in a certain proportion and size for filling during cyanide leaching grinding.

Currently, research on the application of mixed ceramic and steel balls in grinding processes remains relatively limited, particularly in gold cyanide leaching grinding processes. Studies aimed at reducing sodium cyanide consumption by optimizing the material composition and ratio of grinding media are still in their infancy. Based on this, this study was designed and conducted laboratory experiments and industrial production trials, focusing on comparing and analyzing the impact of mixed grinding media ratios on key technical indicators such as grinding product particle size, sodium cyanide consumption, gold recovery rate, and power and media consumption. The study systematically evaluated the adaptability and application feasibility of a mixed ceramic and steel ball ratio under leaching grinding conditions.

2. Materials and Methods

2.1. Materials

This study took a gold concentrate from Gansu Province (China) as its research object. Through scanning electron microscopy (SEM) and BGRIMM process mineralogy analyzer (BPMA) (BGRIMM, Beijing, China) automatic detection and analysis, it was found that the metal sulfides in the ore samples were mainly pyrite, followed by arsenopyrite and magnetite, with trace amounts of chalcopyrite, cuprite, and sphalerite. According to energy dispersive X-ray spectroscopy (EDS) analysis, the primary form of gold in the sample is silver-gold alloy, accounting for 95.98% of the total gold content in the sample; native gold is secondary, accounting for 4.02% of the total gold content. The gangue minerals are primarily carbonate minerals (siderite, calcite, iron dolomite, etc.), followed by quartz and feldspar silicate minerals. The multi-element analysis results of the sample are shown in

Table 1. Multi-element analysis data of samples.

element	Au *	Ag *	Cu	Pb	Zn
Content (%)	31.46	7.72	0.03	0.05	0.006
element	As	Fe	S	C	SiO2
Content (%)	6.54	39.65	39.74	1.08	4.33

* represents unit is g/t.

, and the relative mineral content measurement results are shown in

Table 2. Relative mineral content of samples.

Mineral Name	Content (%)	Mineral Name	Content (%)
Pyrite	67.73	Calcite	4.80
Arsenopyrite	14.13	Siderite	3.40
Pyrrhotite	1.84	Iron dolomite	1.23
Arsenopyrite–galena–pyrite	0.15	Quartz	4.33
Chalcopyrite, Covellite (CuS)	0.07	Kaolinite	0.51
Sphalerite	0.01	Feldspar	0.93
Magnetite	0.33	Others	0.54
Total (%)	100

.

Scanning electron microscopy (SEM) was performed using a TESCAN VEGA3 instrument (TESCAN, Brno–Kohoutovice, Czech Republic). The sample surface was scanned by a high-energy electron beam, and imaging was achieved using secondary electrons (SE) and backscattered electrons (BSE). SE signals primarily reveal surface morphology, while BSE signals are related to the atomic number of elements, providing compositional contrast. Energy-dispersive X-ray spectroscopy (EDS) was conducted with a Bruker XFlash 6130 system (Billerica, MA, USA), coupled with SEM, to obtain qualitative and quantitative elemental analyses by detecting characteristic X-ray energies emitted from the sample under electron beam excitation. The BPMA Version 2.0, a process mineralogy analysis software, was employed in combination with SEM-EDS. By integrating BSE images with EDS spectra, BPMA automatically identifies and quantifies minerals. Using the mineral library, it statistically calculates the process mineralogical parameters of the sample by combining imaging and chemical composition data.

2.2. Grinding Media

The grinding media used in the test were forged steel balls and alumina ceramic balls with diameters of 30 mm, 25 mm, and 20 mm. The density of the forged steel balls is 7.6 g/cm³, with a Rockwell hardness of 60.4; the ceramic balls are alumina ceramic balls produced by the Better wear New Material Co., Ltd. (Beijing, China) (Al₂O₃ ≥ 92%, SiO₂ ≤ 5%), with a density of 3.7 g/cm³ and a Mohs hardness of 9 (estimated Rockwell hardness ≥ 80), as shown in Figure 1.

2.3. Grinding Tests

First, grinding comparison tests were conducted in a ⌀240 × 90 mm conical ball mill using grinding media of different materials but the same ball diameter to assess the feasibility of ceramic balls as grinding media in this grinding system. Based on this, the grinding conditions and parameters for using ceramic balls as grinding media in the grinding of dilute solutions in the gold cyanidation process were studied, specifically exploring the influence of ball charging systems, % solids, and medium filling rates on ceramic ball grinding. Further research was conducted on the effects of mixed filling with steel balls and ceramic balls, as well as different addition ratios, on the particle size characteristics of the grinding product. The specific experimental scheme is shown in

Table 3. Grinding comparison test parameters (grinding time 60 min).

Grinding Media	Filling Rate (%)	Number of Balls	% Solids (%)	Medium Material Ratio (Ceramic Balls: Steel Balls)	Medium Size Ratio (⌀30 mm: ⌀25 mm: ⌀20 mm)
Steel balls	—	180	65	0:1	0:1:0
Ceramic balls	—	180	65	1:0	0:1:0
Steel balls	—	180	65	0:1	1:1:1
Steel balls	—	180	65	0:1	1:1:2
Steel balls	—	180	65	0:1	1:2:2
Ceramic balls	—	180	65	1:0	1:1:1
Ceramic balls	—	180	65	1:0	1:1:2
Ceramic balls	—	180	65	1:0	1:2:2
Ceramic balls	—	180	55	1:0	1:1:2
Ceramic balls	—	180	60	1:0	1:1:2
Ceramic balls	—	180	70	1:0	1:1:2
Ceramic balls	—	180	75	1:0	1:1:2
Ceramic balls	28	—	70	1:0	1:1:2
Ceramic balls	32	—	70	1:0	1:1:2
Ceramic balls	36	—	70	1:0	1:1:2
Ceramic balls	40	—	70	1:0	1:1:2
Ceramic balls	44	—	70	1:0	1:1:2
Ceramic + steel balls	40	—	70	1:1	1:1:2
Ceramic + steel balls	40	—	70	2:1	1:1:2
Ceramic + steel balls	40	—	70	3:1	1:1:2
Ceramic + steel balls	40	—	70	4:1	1:1:2

.

2.4. Comparison Test of Sodium Cyanide Consumption, Iron Leaching Rate, and Gold Leaching Rate

For each grinding test, a sample of 1000 g of gold concentrate with a grade of 31.46 g/t was taken. A ⌀240 × 90 mm conical ball mill (Nanchang Mineral Systems Co., Ltd., Nanchang, China) was used, with a % solids of 70%, a medium filling rate of 40%, and a medium ball diameter mass ratio of ⌀30 mm: ⌀25 mm: ⌀20 mm = 1:1:2. The grinding time was set at 60 min. The study investigated the trends in indicators such as sodium cyanide consumption, iron leaching rate, and gold recovery rate when ceramic balls and steel balls were used separately or mixed in different proportions. The specific ratios of ceramic balls to steel balls were 0:1, 1:1, 2:1, 3:1, 4:1, and 1:0.

After grinding, the slurry underwent a 72-h leaching test under conditions of pH 12 and dissolved oxygen concentration of 7–8 mg/L. To monitor the leaching process, the concentrations of iron ions and gold in the leach solution were determined by atomic absorption spectroscopy (AAS) using an Agilent 240Z AA spectrometer (Agilent Technologies, Santa Clara, CA, USA). AAS is a quantitative technique based on the absorption of specific wavelengths of light by ground-state atoms; after atomization, Fe and Au atoms selectively absorb the characteristic spectral lines emitted by a hollow cathode lamp, with absorbance being directly proportional to the element concentration. Based on these measurements, the gold leaching rate was calculated. The consumption of sodium cyanide is determined by the silver nitrate titration method, using potassium iodide as an indicator. Under alkaline conditions, silver ions react with cyanide ions to form a stable complex. Once the cyanide is completely complexed, excess silver ions react with potassium iodide to produce a precipitate, which marks the titration endpoint. The sodium cyanide concentration is calculated from the volume of the standard silver nitrate solution consumed. The unit consumption of sodium cyanide is expressed as:

$$NaCNconsumption(\mathrm{g}/\mathrm{t})={\displaystyle \frac{NaCNadded\left(\mathrm{k}\mathrm{g}\right)-NaCNresidual\left(\mathrm{k}\mathrm{g}\right)}{oremass\left(\mathrm{t}\right)}}$$

2.5. Grinding Media Wear Test

Under conditions of a % solids of 70%, grinding media size of ⌀25 mm, and a media quantity of 180, experiments were conducted to determine the wear rate (ball consumption) of ceramic balls and steel balls under different grinding times. After the grinding time has elapsed, the grinding media is removed, washed and dried, weighed, and the corresponding test data are recorded.

Table 4. Grinding media wear test plan.

Grinding Media	Media Material Ratio (Ceramic Balls: Steel Balls)	Added Ball Mass (g)	Number of Added Balls
Ceramic balls	1:0	5509.6	180
Steel balls	0:1	14,560.0	180
Ceramic balls + steel balls	1:1	10,034.8	180
Ceramic balls + steel balls	2:1	8526.4	180
Ceramic balls + steel balls	3:1	7772.2	180
Ceramic balls + steel balls	4:1	7319.7	180

gives the specific test plan.

2.6. Industrial Tests

Based on laboratory test results and analysis, an industrial trial involving the mixed use of ceramic balls and steel balls in two MQY1545 ball mills at a gold cyanide smelting plant in Gansu Province, China, was conducted from March to September 2024. The trials focused on analyzing the relationship between grinding medium ratios and grinding efficiency, sodium cyanide consumption, iron leaching rates, and gold recovery rates, as well as the patterns of changes in ball consumption and electricity consumption per ton of ore. The specific industrial trial conditions were as follows: the mass ratio of ceramic balls to steel balls was 3:1, the size ratio of grinding media was ⌀30 mm: ⌀25 mm: ⌀20 mm = 1:1:2, the % solids was 70%, and the media filling rate was 40%. The process flow is shown in Figure 2.

3. Results and Discussion

3.1. Analysis of Grinding Test Results

3.1.1. Analysis of Test Results of Ceramic Balls and Steel Balls in Grinding

Selecting the appropriate material, shape, and size of grinding media facilitates the selective liberation of ore [15,16]. Figure 3 displays the comparison of the grinding product fineness between steel balls and ceramic balls in gold cyanidation. Under the condition of only changing the grinding medium material, the −0.038 mm particle size fraction in the grinding product obtained using ceramic balls is higher than that in the experiments using steel balls. The primary reason for this is that the grinding time set in this study was relatively long (60 min). Under these conditions, although ceramic balls have lower density and weaker unit impact force, they possess higher hardness and excellent wear resistance, primarily relying on shear and friction forces to achieve continuous fine grinding of the ore. This mild and stable grinding mechanism gradually accumulates fine particles over an extended period, ultimately surpassing steel balls in terms of fine particle content. In contrast, steel balls, due to their high density and strong impact force, exhibit a significant grinding advantage in the early stage of grinding, enabling the rapid generation of qualified fine particles in a short time. However, as grinding time increases and ore particle size continues to decrease, the high impact force advantage of steel balls gradually weakens, leading to a decline in re-grinding capacity. Additionally, sustained high-intensity impact may cause some particles to undergo over-grinding [17,18].

When only the size ratio of grinding media is changed, the highest yield of the −0.038 mm particle size fraction in the grinding product is achieved when the mass ratio of medium sizes is ⌀30 mm: ⌀25 mm: ⌀20 mm = 1:1:2. When only a single ball size of ⌀25 mm is used as grinding media, the lowest yield of the −0.038 mm particle size fraction in the grinding product is obtained. This indicates that an appropriate medium size ratio can optimize the filling state of the grinding media, the movement state of particles within the mill, and energy distribution [19], thereby effectively improving the particle size distribution of the grinding product. Grinding media of different diameters exhibit distinct comminution behaviors during the milling process. When a single ball size is employed, the grinding action is generally confined to a limited particle size range, which constrains its effectiveness across the entire size spectrum of the ore. In contrast, an appropriately designed mixture of ball sizes establishes complementary grinding mechanisms within the mill. Coarse grinding is predominantly achieved by larger balls, which impart higher impact energies during collision and effectively fracture coarse particles. Medium-sized balls provide a balance of impact and attrition, thereby improving the breakage efficiency of intermediate-sized particles. Smaller balls, due to their greater number and contact points, predominantly facilitate fine grinding, enhancing the generation of fine-grained fractions. The synergistic interaction among grinding media of different sizes not only optimizes the stress distribution and particle motion within the mill but also promotes a continuous grinding pathway characterized by successive “impact–attrition–fine grinding” mechanisms. Collectively, this leads to improved product size uniformity and enhanced overall grinding efficiency. In this experiment, both ceramic balls and steel balls exhibited the same optimal grinding medium mass ratio of ⌀30 mm: ⌀25 mm: ⌀20 mm = 1:1:2.

3.1.2. Analysis of % Solids Test Results

% solids directly affects the specific gravity, viscosity, and flowability of the slurry. When the % solids is too high, the slurry has poor flowability, making it difficult for the slurry to be quickly discharged from the mill, which can lead to over-grinding of the material. Conversely, when the % solids is too low, the slurry has low viscosity and high flowability, resulting in a lower grinding probability, which may cause the product particle size to fail to meet production requirements. Additionally, the high water content affects the grinding mill’s processing capacity and increases the load on subsequent dewatering operations. An appropriate % solids allows the slurry to effectively adhere to the surface of the grinding media, increasing the grinding probability and improving energy utilization efficiency [20,21]. As shown in Figure 4, the yield of the −0.038 mm and −0.019 mm particle sizes first increases and then decreases with increasing % solids; when it is 70%, the content of −0.038 mm and −0.019 mm in the grinding product is highest, indicating that the grinding efficiency is optimal at this concentration. This is because an appropriate slurry concentration enhances the distribution density of mineral particles in the aqueous phase, increasing the collision frequency between the grinding media and particles, thereby improving grinding efficiency. However, as % solids increases, slurry viscosity and the buoyancy experienced by the grinding media also increase, leading to a weakening of the impact or grinding force exerted by the media, resulting in an overall decline in grinding efficiency. Therefore, a % solids of approximately 70% is the optimal value for ceramic ball grinding.

3.1.3. Analysis of Filling Rate Test Results

The medium filling rate directly affects the effective grinding area inside the mill. When the filling rate is too low, the effective grinding area inside the mill is small, which not only affects the mill’s processing capacity but also results in the ground product’s particle size failing to meet production requirements. When the feed rate to the mill is constant, an excessively high medium filling rate causes some of the medium to not perform grinding functions, and the mill must drag them along during operation. This not only increases the mill’s power consumption and reduces energy utilization efficiency but also increases medium wear, leading to higher grinding costs. An appropriate medium filling rate not only achieves a reasonable distribution of particle size characteristics in the grinding product but also effectively improves energy utilization efficiency and reduces grinding costs [21,22]. As shown in Figure 5, as the filling rate increases from 28% to 44%, the yield of the −0.038 mm and −0.019 mm size fractions in the grinding product first increases and then stabilizes, with the increase in the yield of newly generated −0.038 mm and −0.019 mm particles gradually decreasing. At a filling rate of 28%, the grinding capacity of ceramic balls is insufficient, resulting in a 6.8 percentage point lower yield of the −0.038 mm particle sizes compared to a filling rate of 40%. Therefore, to ensure that ceramic balls have sufficient grinding capacity, the medium filling rate should be maintained above 40%, but it should not be too high, as an excessively high filling rate increases the operational load of the ball mill and may cause ball discharge.

3.2. Analysis of Test Results Comparing Ceramic Balls and Steel Balls with Various Mixture Ratios

Ceramic balls have high hardness and excellent wear resistance, while steel balls have good toughness and impact resistance. Mixing the two in a certain ratio is expected to reduce ball consumption and energy consumption per ton of ore while achieving optimal grinding results. As shown in Figure 6, when only the ratio of ceramic balls to steel balls is changed, the yield of the −0.038 mm size fraction in the grinding product increases as the proportion of ceramic balls increases. When the ratio of ceramic balls to steel balls reaches 3:1, the yield of the −0.038 mm size fraction in the grinding product exceeds the fineness of the grinding product obtained by using ceramic balls alone. When the proportion of ceramic balls continues to increase, the yield of the −0.038 mm size fraction in the grinding product remains essentially unchanged.

3.3. Analysis of Test Results for Sodium Cyanide Consumption, Iron Leaching Rate, and Gold Leaching Rate

During the grinding process, steel balls produce some metal ions due to wear, and these ions may cause some side reactions in the cyanide solution, affecting the efficiency of cyanide leaching [23]. As shown in Figure 7, as the proportion of ceramic balls in the grinding medium gradually increases, the concentration of iron ions in the lean liquid grinding medium decreases gradually, from 4230 mg/L to 3926 mg/L, a decrease of 304 mg/L, indicating that as the number of steel balls decreases, the release of iron ions decreases significantly. Under identical conditions, after 72 h of leaching, the gold grade in cyanidation residue decreased from 2.03 g/t to 1.95 g/t, a decrease of 0.08 g/t; the gold leaching recovery rate increased from 93.55% to 93.80%, an increase of 0.25 percentage points. When the ratio of ceramic balls to steel balls reached 3:1, the gold leaching rate of the mixed grinding medium filling scheme reached the level of the pure ceramic ball scheme. The sodium cyanide consumption also decreased from 11.3 kg/t to 10.5 kg/t, a reduction of 0.8 kg/t. When the ratio of ceramic balls to steel balls reached 4:1, the sodium cyanide consumption of the mixed grinding medium filling scheme was consistent with the indicators of the all-ceramic ball scheme.

The steel ball-only scheme shows a rapid increase in recovery rate during the initial grinding stage, but as time progresses, recovery rate growth slows due to steel ball wear and potential chemical reactions. In contrast, the ceramic ball-only scheme has a relatively weak grinding capacity, resulting in a lower recovery rate during the early grinding stage. However, due to the stable chemical environment of ceramic media, the recovery rate improves to some extent during the later grinding stage. Additionally, by using mixed media, the fineness of the grinding product is improved, effectively increasing the exposed surface area of gold, which positively impacts the enhancement of gold leaching rates.

3.4. Analysis of Grinding Media Consumption Test Results

During the operation of a ball mill, grinding media inevitably undergo wear. Reducing the media wear rate is a critical step in minimizing production costs. As shown in

Table 5. Grinding media wear test results.

Media Material Ratio (Ceramic Balls: Steel Balls)	Added Ball Mass (g)	Remaining Medium Mass After 10 h of Grinding (g)	Loss After 10 h of Grinding (g)	Loss Rate After 10 h of Grinding (kg/t)	Remaining Medium Mass After 100 h of Grinding (g)	Loss After 100 h of Grinding (g)	Loss Rate After 100 h of Grinding (kg/t)
0:1	14,560.0	14,509.0	51.0	3.50	14,184.4	375.6	25.8
1:1	10,034.8	10,004.0	30.8	3.07	9806.8	228.0	22.7
2:1	8526.4	8502.8	23.6	2.77	8364.1	162.3	19.0
3:1	7772.2	7755.4	16.8	2.16	7634.7	137.5	17.7
4:1	7319.7	7305.4	14.3	1.95	7219.4	100.3	13.7
1:0	5509.6	5499.0	10.6	1.92	5438.5	71.1	12.9

and Figure 8, the amount of media wear increases with the prolonged operation time of the ball mill under different grinding media schemes. At the two time points of 10 h and 100 h of grinding, the media wear rate decreases significantly with an increase in the proportion of ceramic balls added. When only steel balls are used as grinding media, the media loss rate reaches 2.58% after 100 h of grinding; whereas when only ceramic balls are used as grinding media, the media loss rate under the same conditions is 1.29%. This indicates that the wear rate of ceramic balls in a laboratory ball mill is approximately half that of steel balls.

In a mixed ball charging system, the differences in hardness and surface characteristics between ceramic balls and steel balls cause changes in the collision wear patterns between them. At the same time, the presence of ceramic balls changes the movement trajectory and collision frequency of the balls inside the ball mill, thereby reducing the overall wear of the balls [13].

Compared to the traditional single steel ball loading method, the mixed loading of ceramic balls and steel balls demonstrates higher stability and better recovery rates throughout the grinding–leaching process. In the traditional steel ball loading scheme, after prolonged grinding, steel ball wear releases a large amount of iron impurities, leading to increased iron ion concentrations in the slurry, which interfere with the cyanide leaching reaction, affect the effective leaching of gold, and ultimately limit improvements in gold recovery rates. In the mixed loading scheme, the introduction of ceramic balls effectively mitigates the adverse effects of steel ball wear. By reasonably optimizing the mixed ball, the advantages of both materials can be fully utilized to enhance grinding efficiency and cyanide leaching efficiency, thereby improving gold recovery rates. Therefore, considering the actual production requirements for medium filling rate and processing capacity, it is recommended to adopt a mixed ball charging scheme with a mass addition ratio of ceramic balls to steel balls of 3:1 and a ball diameter ratio of ⌀30 mm: ⌀25 mm: ⌀20 mm = 1:1:2.

3.5. Analysis of Industrial Application Results

3.5.1. Analysis of Industrial Production Indicators

As shown in

Table 6. Industrial test results.

Grinding Media	Feed −0.038 mm Content (%)	Discharge −0.038 mm Content (%)	Change in Iron Ions (g/m3)	Cyanide Consumption in Grinding (kg/t)	Total Cyanide Consumption (kg/t)	Gold Recovery Rate (%)	Ball Consumption (kg/t)	Mill Current (A)
Steel balls	55.0	67.2	302.0	4.5	20.3	93.6	1.73	220
Ceramic + steel balls	55.0	64.1	77.0	3.7	19.0	93.9	0.93	151
Ceramic balls	55.0	66.9	52.0	3.6	18.5	93.9	0.75	135

, under the condition that the ore processing volume remains unchanged, the use of different grinding media schemes has a significant impact on indicators such as grinding product fineness, iron ion content, sodium cyanide consumption, gold recovery rate, and energy consumption.

Grinding product fineness: When steel balls are used as grinding media, the yield of the −0.038 mm particle size fraction in the ball mill discharge is 64.1%; when ceramic balls are used as grinding media, the fineness of the ball mill discharge (−0.038 mm) is 67.2%; when using a mixture of ceramic balls and steel balls as grinding media, the ball mill discharge fineness (−0.038 mm) is 66.9%; compared to the steel ball-only scheme, the ceramic ball scheme improves grinding fineness by 3.1 percentage points; the mixture scheme improves grinding fineness by 2.8 percentage points.

Iron ion content and sodium cyanide consumption: Using the steel ball scheme, the iron content in the ball mill discharge slurry increased by 302 mg/L compared to the feed end; using the ceramic ball scheme, the iron content in the ball mill discharge slurry was 52 mg/L higher than at the feed end; using the mixed ceramic and steel ball scheme, the iron content in the ball mill discharge slurry was 77 mg/L higher than at the feed end. This indicates that adding a portion of ceramic balls to replace steel balls during grinding can effectively reduce the amount of iron entering the slurry.

Correspondingly, the total sodium cyanide consumption for the steel ball scheme was 20.3 kg/t; for the ceramic ball scheme, it was 18.5 kg/t; and for the mixed ceramic and steel ball scheme, it was 19.0 kg/t. Compared to the steel ball-only scheme, the ceramic ball scheme reduced total sodium cyanide consumption by 1.8 kg/t, a decrease of 8.87 percentage points; the mixed scheme reduced total sodium cyanide consumption by 1.3 kg/t, a decrease of 6.40 percentage points.

Gold recovery rate: When traditional steel balls are used as grinding media, the gold recovery rate is 93.6%; however, when ceramic balls or a mixed ceramic–steel ball grading scheme is employed, the gold recovery rate reaches 93.9%. The ceramic ball scheme and the mixed scheme can increase the gold recovery rate by 0.3 percentage points compared to the steel ball scheme.

Energy consumption and ball consumption: When using steel balls as grinding media, the mill operating current is approximately 220 A, with steel ball consumption of 1.73 kg/t. When using ceramic balls as grinding media, the mill operating current is approximately 135 A, with a ceramic ball consumption rate of 0.75 kg/t. When using a mixture of ceramic and steel balls as grinding media, the mill operating current is approximately 151 A, with a media ball consumption rate of 0.93 kg/t. Compared to the scheme using only steel balls, the scheme using only ceramic balls reduces the grinding power consumption per ton of ore by approximately 38.64 percentage points and the grinding medium consumption by 56.65 percentage points; the scheme using a mixture of ceramic and steel balls reduces the grinding power consumption per ton of ore by approximately 31.36 percentage points and the grinding medium consumption by 46.24 percentage points, both demonstrating significant energy-saving and consumption-reduction effects.

By replacing steel balls with ceramic balls as grinding media, the electricity consumption per ton of ore decreased by approximately 38.64 percentage points, the consumption of grinding media decreased by 56.65 percentage points, and the consumption of sodium cyanide per ton of ore decreased by 8.87 percentage points. All indicators showed significant improvements. However, when the grinding product fineness reached the same level as when using steel balls, the mill’s processing capacity decreased by over 15%. To address the issue of insufficient mill processing capacity, an attempt was made to increase the mill filling rate to 44%, but a noticeable “ball discharge” phenomenon occurred during mill operation. Given this, to improve indicators while balancing mill processing capacity and grinding efficiency, it is advisable to adopt a mixed filling scheme using ceramic and steel balls.

3.5.2. Analysis of the Economic Benefits of Industrial Production

Based on an annual processing capacity of 50,000 tons of flotation gold concentrate with a grade of 31.46 g/t and a sodium cyanide unit price of 15,600 yuan/t, the cost analysis and economic benefit calculations are shown in Figure 9.

As shown in Figure 9, compared with the traditional single steel ball scheme, the use of a mixed ceramic ball and steel ball scheme as grinding media can save 134,000 yuan in ball consumption costs annually, 1,014,000 yuan in cyanide consumption costs annually, and 157,000 yuan in grinding power consumption costs annually. The improvement in recovery rate indicators can generate an additional economic benefit of 3,633,600 yuan. In summary, the mixture scheme can generate an additional economic benefit of 4,938,600 yuan annually.

4. Conclusions

This study systematically evaluated the combined use of ceramic balls and steel balls in the fine grinding process of horizontal mills for gold cyanidation leaching. The experimental results indicate that by reasonably combining the loading and size ratio of ceramic balls and steel balls, the fineness of the grinding product (−0.038 mm) can be increased by over 2.8%, gold recovery rate improved by 0.3%, and sodium cyanide consumption reduced by 1.3 kg/t, fully demonstrating the significant advantages of the synergistic effect between ceramic balls and steel balls.

Under the condition of unchanged processing capacity, the mixed ball medium significantly reduces the power consumption and ball consumption per ton of ore in the ball mill, decreasing by 31.36% and 46.24%, respectively. Through industrial trials at a gold smelting plant in Gansu Province, annual savings of 134,000 yuan in ball consumption costs, 1,014,000 yuan in cyanide consumption costs, and 157,000 yuan in electricity consumption costs were verified. Additionally, the improved gold recovery rate generates an additional economic benefit of 3,633,600 yuan, resulting in an annual comprehensive economic benefit of nearly 5 million yuan. This provides a new pathway for enterprises to achieve energy conservation, emission reduction, quality improvement, and efficiency enhancement.

As gold resources become increasingly depleted and environmental pressures continue to intensify, improving metal recovery rates, reducing reagent consumption, and minimizing pollutant emissions have become core objectives for the gold industry. The process using ceramic balls and steel balls not only meets the urgent demand for efficient, environmentally friendly, and low-consumption solutions in current gold cyanide leaching processes but also provides a referenceable solution for other precious metal cyanide leaching and hydrometallurgical industries.

The ceramic balls used in this study are mainly made of aluminum oxide as the base material. No comparative studies have been conducted on the adaptability and effectiveness of ceramic balls made of other components (such as zirconium oxide, silicon oxide, etc.) in the grinding process. Given that the material of ceramic balls may have a significant impact on key indicators such as the particle size distribution of the grinding product and sodium cyanide consumption, subsequent work will further expand the types of ceramic media and conduct in-depth studies on their performance differences and mechanisms of action.