Evaluation of Georgian bentonite clay as a natural adsorbent for copper(II) ion removal from mining-contaminated water: implications for reducing heavy-metal-related disease burden

Authors

  • Giorgi Tkeshelashvili Universidad Carlos III de Madrid, Spain

DOI:

https://doi.org/10.66636/gmj.v1.i2.a4

Keywords:

bentonite clay, copper(II) adsorption, heavy metal contamination, mining wastewater, environmental health, water remediation, Georgia, public health

Abstract

Background  Heavy-metal contamination of surface water from mining operations constitutes a major environmental and public-health concern worldwide. In the Bolnisi district of south-eastern Georgia, unregulated discharge from copper and gold mining has elevated copper(II) concentrations in the Kazretula and Mashavera rivers far above the World Health Organization (WHO) drinking-water guideline value of 2 mg/L. Bentonite clay, a montmorillonite-rich aluminosilicate with high cation-exchange capacity, offers a low-cost natural adsorbent for heavy-metal remediation. Georgian bentonite deposits in the Ascana region (Ozurgeti) have not previously been evaluated for this application in the indexed literature.

Methods  A controlled laboratory study was conducted to evaluate the temperature dependence of copper(II) adsorption by Georgian calcium bentonite clay. Naturally contaminated water from the Kazreti mining region (baseline Cu²⁺ concentration 0.0356 mol/L; approximately 2,262 mg/L) was treated with 5.0 g of bentonite clay per 100 mL at five temperatures (20, 40, 60, 80, and 100 °C) with 30-minute contact time, each in quintuplicate (n = 25 total experiments). Residual Cu²⁺ was quantified by UV-Vis spectrophotometry at 614 nm against a five-point calibration curve (R² = 0.980).

Results  Mean adsorption efficiency increased monotonically with temperature: 34.8% (SD 3.1) at 20 °C, 50.3% (SD 2.3) at 40 °C, 58.9% (SD 2.6) at 60 °C, 68.8% (SD 2.0) at 80 °C, and 85.6% (SD 1.7) at 100 °C. The 2.5-fold increase in efficiency across the temperature range, together with the consistently low intra-group variability (coefficient of variation 2.0–8.9%), is consistent with an endothermic chemisorption process. At 80 °C and above, the filtrate was visually colourless, indicating near-complete copper removal.

Conclusions  This study provides the first systematic evaluation of a Georgian bentonite clay for heavy-metal remediation in the indexed literature. Georgian calcium bentonite demonstrates substantial and temperature-dependent adsorption capacity for copper(II) ions from mining-contaminated water, with efficiency approaching 86% at 100 °C (ANOVA F(4,20) = 218.4; p < 0.001). These findings support the potential use of a locally sourced, low-cost adsorbent as a component of water-remediation strategies in the Bolnisi mining district. Further research on adsorption isotherms, competitive multi-metal removal, desorption kinetics, and pilot-scale field deployment is warranted.

Keywords  bentonite clay; copper(II) ions; heavy metal contamination; adsorption; wastewater treatment; Kazreti; Georgia; environmental health; mining remediation

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Cover of the Georgian Medical Journal (GMJ), Volume 1, Issue 2 (2026), titled “Health Systems Performance and Quality of Care: Measurement, Improvement, and Outcomes,” with a blue world map background representing global health connectivity. Includes the themes “Quality, Safety, Results” and the publisher Public Health Institute of Georgia.

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Published

05/12/2026

How to Cite

Tkeshelashvili, G. (2026). Evaluation of Georgian bentonite clay as a natural adsorbent for copper(II) ion removal from mining-contaminated water: implications for reducing heavy-metal-related disease burden. Georgian Medical Journal, 1(2), 1–10. https://doi.org/10.66636/gmj.v1.i2.a4

Issue

Vol. 1 No. 2 (2026): Health Systems Performance and Quality of Care

Section

Original Research

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