Reduction of Nitrate in Water Using Acid and Iron-Modified Biochar
Document Type : Research Paper
Authors
1 Department of Soil Science Engineering, Faculty of Agricultural Sciences, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
2 Soil Science and Engineering Department, Faculty of Agricultural Sciences, Sari Agricultural Sciences and Natural Resources University, Sari, Iran
Abstract
The presence of nitrate in drinking water is a major global concern. Various methods have been explored for nitrate removal, among which adsorption using low-cost and readily available adsorbents holds a special position; however, challenges remain in the adsorption of anions such as nitrate. In this study, biochar derived from rice straw, produced at 600 °C, was evaluated as a nitrate adsorbent. To enhance adsorption performance, the biochar was modified with 1 N hydrochloric acid and with trivalent iron at two different pH values (2 and 6). Experiments were conducted in a randomized design to compare the efficiency of different treatments. Results indicated that all treatments improved nitrate adsorption, with the highest uptake observed for iron-modified biochar at pH 2, showing approximately 53% higher adsorption than unmodified biochar. Optimization revealed that maximum adsorption occurred at a contact time of 90 minutes and pH 3. In examining the effect of adsorbent dose, 0.625 g/L provided the highest adsorption capacity per unit mass, although increasing the adsorbent dose increased the overall nitrate removal percentage. Furthermore, increasing the initial nitrate concentration up to 100 mg/L raised the adsorption capacity to about 30 mg/g. Adsorption isotherm analysis indicated that the Langmuir model provided the best fit. These findings suggest that rice straw biochar produced at 600 °C and modified with trivalent iron at pH 2 can serve as an effective adsorbent for nitrate removal from aqueous environments.
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