Impact of Recirculating Mining Process Water on the Flotation Performance of a Sedimentary Phosphate Ore

Abstract

Water is one of the scarce resources in the world and the mining industry like many other sectors is expected to discretionally utilise this resource sustainably. It was on the premise of adding to the body of knowledge related to water sustainability and flotation performance that an investigation was prompted to evaluate the impact of recirculating mining process water on the flotation performance of a sedimentary phosphate ore. A series of flotation locked cycle tests were conducted with the objective to simulate recycling process water, which by default modifies the water chemistry and influences flotation performance. The laboratory flotation results showed that recycling process water in the laboratory scale did not show significantly noticeable influence on P2O5 grade and recovery performance. A saleable product of 33.27% P2O5 grade at reasonable average recovery of 65% was achievable. Water analyses revealed that there was an increase in total dissolved solids [452 to 846mg/L], electrical conductivity [662 µm/cm to 1025 µm/cm], CaCO3 [146 to 304mg/L], sodium [57.7 to 76.6mg/L], chloride [100.7 to 109.7mg/L] and magnesium [10.4 to12.6mg/L] after circulating the process water for 15 cycles. The results achieved however confirmed the importance of water quality and understanding process water chemistry in flotation processes. The compounding salts and inorganic elements in the water necessitate the need for water clarifiers for process water prior to being recycled to the flotation process.

The Effect of Water Circulation on Bulk Flotation Performance of a Polymetallic Sulphide Ore

“…The ore also contains significant quantities of Al, Si, S and Mn with the main gangue being Si. The significant amount of silicon found in the raw Black Mountain ore sample is in correspondence to what was discovered by [6] and the rest of the XRF results below corresponds to what has already been discovered in existing research.…”

“…The TDS increased from 115.5 mg/L to a range of 1390-2460 mg/L for all tests conducted and the TSS increased from 72 mg/L to 968 mg/L as the flotation process took place and as the water was being circulated. A similar observation of increasing TDS in circulated flotation process water was observed in a study conducted by [6]. The increase in both the TDS and the TSS values shows that the two water quality factors have a directly proportional relationship with the addition of flotation reagents, the more the flotation reagents are added, the more both factors increase although the increase is not consistent.…”

“…The electrical conductivity as seen on the graph below increased from 0.23 mS/cm to 4.92 mS/cm. The inverse relationship between the pH and the electrical conductivity of the recycled process water had no significant negative impact on the flotation performance but rather facilitated the flotation of the valuable products over that of the gangue and a similar observation was made in a previously conducted research [6]. The impact of recirculating process water on TDS and TSS was investigated and the results are shown in Fig.…”

“…The highest peak from the XRD patterns mainly occur between 25 and 30 degrees on the horizontal axis which is where the minerals Quartz and Sillimanite are found. This then goes to prove that the Black Mountain ore used in this project has high quantities of crystalline silicon which is in correspondence to what has already been discovered from the XRF results above and from the study conducted by [6]. As it is already known from literature that Black Mountain ore is a primary host of copper, lead and zinc sulphide minerals , the second highest peak on the graph occurs where the minerals galena (sulphide host of lead) and chalcopyrite (sulphide host of copper) are found represented by the letters D and C and there are also visible peaks of the letter A indicating a sulphide host of the zinc metal.…”

“…Table 2 shows the elemental composition of the raw BM ore pulverized sample obtained using XRF analysis. The main abundant element present in the ore is iron (Fe) with a composition of 31.56 % which is often associated with copper minerals in most ores according to existing literature [6]. BM ore is a primary host of copper, lead and zinc sulphides [4] and therefore, there are significant quantities of Cu, Pb and Zn elements present in the ore with percent compositions of 0.19, 3.17 and 3.90 respectively.…”