Researchers Pioneer Multi-Tech Treatment for Mine Water Contamination

By Dr. Noopur JainReviewed by Laura ThomsonMay 31 2024

In a recent article published in the journal Water, researchers from China highlighted the challenges faced by the mining industry in treating wastewater contaminated with heavy metals and inorganic salts. The study also introduced an approach using a combination of precipitation, adsorption, and bipolar membrane electrodialysis (BMED). Researchers aim to provide effective and efficient solutions for treating contaminated mine water and promoting responsible resource extraction practices by optimizing the synergistic effects of different treatment methods.

Background

Developing innovative treatment strategies is imperative for advancing sustainable mining practices and mitigating the environmental impact of mine water discharge. Traditional methods have limitations in effectively removing the pollutants generated during mining, highlighting the need for innovative approaches.

The mining industry plays a crucial role in meeting the global demand for mineral resources, but it also generates significant environmental challenges, particularly mine water contamination. Untreated mine water discharge can increase surface water and groundwater salinity, impacting aquatic life and human health.

In China alone, the annual discharge of mine water amounts to billions of tons, contributing substantially to industrial wastewater pollution. Despite the scale of this issue, the treatment rate for mine water remains low, highlighting the urgent need for efficient and environmentally friendly remediation technologies.

Conventional single-treatment methods for mine water have limitations in effectively removing the diverse range of pollutants present, including metal ions, organic matter, and suspended solids. As a result, there is a growing recognition of the need for combined treatment approaches that leverage multiple technologies to achieve comprehensive water remediation.

The Current Study

The present study combined precipitation, adsorption, and bipolar membrane electrodialysis to treat simulated mine water contaminated with heavy metals and sulfate. The experimental setup consisted of controlled tests to optimize the treatment process.

For the precipitation stage, a solution containing NaOH and BaCl₂ was used as the precipitant to facilitate the removal of heavy metals from the mine water. The solution's pH, temperature, and stirring speed were carefully controlled to ensure efficient precipitation of the metal ions.

In the adsorption stage, humic acid was utilized as the adsorbent to further enhance the removal of heavy metals from the water. The adsorbent dosage, contact time, and agitation rate were varied to determine the optimal conditions for maximum adsorption efficiency.

The BMED process was then employed to target sulfate removal and acid recovery from the treated water. The experimental parameters included an electrode liquid concentration of 0.1 mol/L, an operating voltage of 12 V, an initial salt concentration of 30 g/L, and a flow rate of 3.5 mL/min. The desalting rate, current efficiency, and energy consumption were monitored to assess the performance of the BMED system.

Parallel experiments were conducted to validate the results and ensure the reproducibility of the treatment process. Data on mine water stages were collected, including the removal efficiencies of Cd²⁺, Mn²⁺, Cu²⁺, and SO₄^2-, as well as the overall removal rates achieved through the combined precipitation-adsorption-BMED approach.

The experimental study provided valuable insights into the effectiveness of the multi-technology coupled treatment process for mine water remediation, highlighting the potential for practical application in real-world mining wastewater treatment scenarios.

Results and Discussion

The study successfully demonstrated the effectiveness of a combined precipitation-adsorption-BMED approach for treating mine water contaminated with heavy metals and sulfate. The optimized operating conditions for each stage of the treatment process led to significant removal efficiencies and recovery rates.

During the precipitation phase, utilizing NaOH and BaCl₂ as precipitants resulted in substantial removal rates of heavy metals, notably Cd²⁺, Mn²⁺, and Cu²⁺, exceeding 95%. The BMED process focused on sulfate removal and acid recovery, demonstrating impressive desalting rates of up to 96.8% and current efficiencies of 58.2%.

In the adsorption stage employing humic acid as the adsorbent, the optimized conditions, including solution pH, reaction temperature, adsorbent dosage, reaction time, and stirring speed, achieved exceptional removal efficiencies of Cd²⁺, Mn²⁺, and Cu²⁺, surpassing 99% in some instances. This stage was pivotal in meeting the desired water quality standards for heavy metal concentrations. Moreover, the successful acid recovery from the wastewater highlighted the combined treatment strategy's sustainability and resource recovery potential.

Conclusion

The study underscores the potential of the Combination of Precipitation-Adsorption-BMED process for mine water treatment. The successful removal of heavy metals and sulfate, coupled with the recovery of valuable resources from the wastewater, showcases the promise of the multi-technology coupled treatment process.

This approach offers a promising solution to water pollution challenges in the mining industry by effectively removing heavy metals and inorganic salts. Further research and implementation of this innovative method could significantly contribute to sustainable mining practices and environmental protection.