Enhancing the removal of total trihalomethanes and dissolved organic matter from water using zinc and iron-impregnated granulated activated carbon and response surface methodology

In this study, activated carbon (AC) impregnated with zinc (Zn) and iron (Fe) was assessed for its ability to remove total trihalomethanes (TTHMs), humic acid (HA), and dissolved organic carbon (DOC) from water. Utilizing Design of Expert software, 32 experimental setups were conducted to optimize variables like adsorbent dose, pH, temperature, shaking speed, and contact time. Results showed that AC enriched with a higher concentration of metals (2 M Fe-Zn-IAC) was most effective, particularly at higher doses and extended contact times. The maximum removal rates were 98 % for TTHMs and 82 % for HA under conditions of neutral pH, 200 rpm shaking speed, 30 °C, and a 3-hour contact period. A cubic model accurately predicted the removal efficiencies. Optimization further refined the conditions to a 48 mg/L dose at 20 °C, pH 8, and 150 rpm for 2 h, achieving 93.49 % TTHM and 89.35 % DOC removal, with a desirability value of 0.963. Overall, granulated AC with a relatively high concentration of multi-metal impregnation proved to be the best adsorbent for the removal of THMs and HA from water at high doses and contact times. This research contributes to sustainable water treatment methods and supports the United Nations Sustainable Development Goal of clean water and sanitation. Further studies are recommended to test this adsorbent under varied environmental conditions. • Zinc-iron activated carbon (AC) enhances removal of TTHMs, DOC, and HA in water treatment. • 2 M Fe-Zn-AC achieved 98 % TTHMs and 82 % HA removal in lab tests. • Cubic model fits TTHMs ( p < 0.0003) and DOC ( p < 0.0015) removal. • RSM optimized the conditions with desirability value of 0.963. • Optimal conditions: 47.96 mg/L AC, 20 °C, pH 8, 150 rpm, 2 h contact time