The formation of harmful algal blooms due to elevated nutrient levels especially phosphates in aquatic environment has become a major concern. It is crucial to reduce the levels of phosphate from wastewater sources (e.g. concentrated animal feeding operations and municipal treatment plants) before discharge to alleviate the eutrophication. Mg-impregnated biochar has been shown as a promising low-cost adsorbent for phosphate removal. The powder form of Mg-biochar provides enormous sites for high phosphate adsorption capacity. However, it is difficult to separate and recover Mg-biochar after treatment for further recycle and reuse. In this study, magnetic biochar containing varying magnesium contents was synthesized, characterized and optimized for removing phosphates from aqueous solutions. The SEM and TEM showed the formation of nanosized iron and magnesium oxides in biochar matrix. Sorption ability increased with increasing Mg content, and the magnetic biochar with 20% Mg content exhibited the highest phosphate removal capacity of 121.25 mg P/g at pH 4.0. XRD and FTIR analysis before and after adsorption revealed that the dominant sorption mechanisms involved were surface electrostatic attraction and precipitation between MgO and phosphate. In addition, the potting study showed that the recovered magnetic MgO-biochar loaded with phosphate after treating swine wastewater significantly increased ryegrass growth. Overall, this work demonstrated that engineered magnetic biochar composites impregnated with magnesium oxides can be used as cost-effective adsorbents for phosphate and secondary use as fertilizer after separation following wastewater remediation.

Recycling phosphate with MgO decorated magnetic biochar composite and its potential use as fertilizer

255th National Meeting (2018)

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