UNTAN's RESchorbic Team Tackles Mercury Contamination in Post-Mining Soil

PONTIANAK – What can be done when soil from former gold mining sites remains contaminated with mercury? This question served as the starting point for a group of students from Universitas Tanjungpura (UNTAN) who are exploring a solvent-based approach to help reduce mercury levels in the soil.

The research was conducted by the RESchorbic team through the 2026 Student Creativity Program for Exact Research (PKM-RE). The samples used were taken from soil previously affected by gold mining activities in Landak Regency, West Kalimantan.

The team developed a Natural Deep Eutectic Solvent (NADES) system based on choline chloride (ChCl) and ascorbic acid (AA). In this study, NADES was used as a medium to assist in transferring mercury from the soil matrix into the solvent phase.

This approach was tested through several stages. The team first sought a composition of ChCl and AA with characteristics suitable for the remediation process.

Finding the Right Formula

Several ratios of choline chloride and ascorbic acid were tested. Among the formulations used in the study, a 2:1 ratio of ChCl to AA demonstrated more stable and homogeneous characteristics.

This formulation was then used to test the ability of NADES to help reduce mercury from the soil.

During the remediation stage, the soil was brought into contact with NADES using various ratios. Test results showed that the optimal conditions achieved a mercury removal efficiency of up to 99.31 percent.

These results were obtained in laboratory-scale testing using a soil-to-NADES ratio of 1:15.

While this figure is a key finding of the research, the team did not focus solely on the amount of mercury removed from the soil.

The mercury that had transferred into the NADES phase was then separated through a precipitation process using sodium sulfide. This process produced a black precipitate identified as mercury sulfide (HgS).

This stage is part of an effort to ensure that the mercury removed from the soil is not just contained within the solvent phase, but can also be isolated for further management.

Attempting Solvent Reuse

In addition to remediation capability, the team also tested the feasibility of reusing the NADES.

The used NADES was reprocessed and tested through several cycles. The results showed that the system could still be reused, although its performance changed in subsequent applications.

The reuse of solvents is an interesting aspect for further development, as it relates to the efficiency of material usage in the remediation process.

Beyond Measuring Mercury Levels

The RESchorbic research also examined the condition of the soil after treatment.

Characterization was performed to observe changes in the soil material following the remediation process. Based on the results, no major changes were found in the soil's primary mineral structure.

The team then used mung bean sprouts to observe the biological response of the soil after treatment. Observations showed that sprouts grown in the remediated soil exhibited better growth compared to soil that had been conditioned with mercury prior to the remediation process.

These observations complement the research, as the success of remediation can be measured not only by changes in contaminant levels but also by the condition of the soil after treatment.

Still in the Laboratory Testing Stage

Although it demonstrated a removal efficiency of up to 99.31 percent, this research is still in the laboratory testing stage.

"We hope there will be follow-up research to explore many aspects related to this study,"said Jason.

Therefore, these figures cannot yet be interpreted as proof that the system is ready to be applied to all types of post-mining soil. Further research is still needed to test the NADES system on more diverse soil characteristics, optimize solvent reuse, and evaluate its application on a larger scale.

The RESchorbic team consists of Jason Robiansa Agustian, Citra Widiasari, Muhammad Fiqri Aulia Rahman, Siti Hutsiyah, and Vika, under the guidance of Ferdinand Hidayat from the Department of Chemistry at Universitas Tanjungpura.

Through this research, the team carries the spirit of "Green Solution for Soil Restoration" in exploring chemistry-based approaches to assist in the recovery of soil impacted by mining activities.