University laboratories are hubs of innovation, but they often produce a hazardous byproduct: toxic wastewater. At the University of Mataram, for example, the Soil Chemistry Laboratory’s daily operations generate wastewater contaminated with dangerous heavy metals like mercury (Hg) and chromium (Cr). In many labs, this toxic liquid is simply diluted and poured down the drain, posing a direct threat to ecosystems and human health, as these metals can bioaccumulate and cause severe diseases. A new study by Hendra R. Akhdiyat and colleagues, published in Jurnal Pijar MIPA, tackles this problem with a simple, effective, and environmentally friendly filter. The researchers turned to adsorption, a reliable method where pollutants stick to a material’s surface. They chose a team of three low-cost, natural adsorbents: biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More, zeolite, and activated alumina. Biochar, a charcoal-like substance made from agricultural waste, grabs organics and metals. Zeolite, a porous mineral, traps other metal ions. Activated alumina “polishes” the water, removing color and turbidity. The goal was to see if this combination could work synergistically—achieving more together than they could alone.

The team’s hypothesis about synergy was correct. When tested individually, the materials showed their own strengths but also their limits. Ten grams of biochar, for instance, was the best at removing mercury (82.9%) but less effective on chromium (70.13%). Activated alumina showed a more balanced, but lower, performance (74.3% Hg, 71.27% Cr). Zeolite lagged behind on its own (64.4% Hg, 58.93% Cr). The real breakthrough came with the 1:1:1 combination. This “EQA” mix (Biochar + Zeolite + Activated Alumina) immediately outperformed all other combinations, demonstrating a true synergistic effect. Even a small 10-gram dose of this mix (3.33g of each) removed 93.4% of mercury and 87.97% of chromium. It also did the best job by far at clearing the water’s cloudiness, or total suspended solids (TSS), reducing it by over 61%. Encouraged, the researchers then tested what would happen if they increased the dosage of this winning formula. They ran tests with 15g, 20g, 25g, and 30g of the EQA mix. The results were clear, linear, and statistically significant: the more adsorbent used, the cleaner the water became. The optimal 30-gram dose (10g of each material) achieved a stunning success rate: it removed 99.5% of the mercury and 98.3% of the chromium. It also made the wastewater much clearer, cutting turbidity by nearly 80%, all while conveniently keeping the pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More in a safe, neutral range.

A 99.5% removal rate is a major victory, especially for a solution that is economical and environmentally friendly. This research provides a practical blueprint for facilities like the Soil Chemistry Laboratory to move away from the harmful “dilute and dump” practice. Using biochar, which is made from agricultural waste, is a particularly clever part of the solution. It supports a circular economy by turning a waste product into a valuable tool for cleaning up other waste. However, the study also provides a critical dose of realism. The fight against heavy metal pollution is incredibly difficult because the acceptable “safe” limits are near zero. Even after removing 99.5% of the mercury, the final concentration in the water was still higher than the strict 0.005 mg/L limit set by Indonesian government regulations (PP No. 22 of 2021). The final chromium level was also just above its 0.5 mg/L legal limit. This does not mean the filter is a failure; it means it is a powerful and highly effective first step. The researchers conclude that this EQA adsorbent has great potential, but further optimization is needed. To meet those final environmental standards, labs may need to increase the adsorbent dose, re-engineer the filter’s structure, or use this adsorption method as part of a larger, multi-stage treatment process.

Source : Akhdiyat, H. R., Sukartono, S., Jasrodi, J., & Putra, H. S. (2025). Adsorption-Based Laboratory Hazardous Waste Treatment with a Combination of Biochar, Zeolite, and Activated Alumina as an Environmentally Friendly Solution. Jurnal Pijar MIPA, 20(6), 1199–1203.