Organic particles and high pH in food waste anaerobic digestate enhanced NH4+ adsorption on wood-derived biochar

作者：Yunyun Zheng, Nanthi Bolan, Sue Jenkins, Bede S. Mickan · 发表于：The Science of The Total Environment · 年份：2024 · DOI：10.1016/j.scitotenv.2024.174458 · 被引用次数：14 · 研究领域：Adsorption and biosorption for pollutant removal、Phosphorus and nutrient management、Constructed Wetlands for Wastewater Treatment

Biogas residues (i.e., digestate) are rich in NH4+ that has great agricultural value but environmental risk if not recycled. Biochar can be an effective adsorbent retaining NH4+ from digestate. However, it remains unclear how the unique composition of digestate affects the capacity and mechanisms of NH4+ adsorption on biochar. This study examined the mechanisms and driving factors of NH4+ recovery from digestate containing different molecular-weight organic particles by using wood-derived biochar with or without H2O2 modification. Four solutions were prepared, including pure NH4+, synthetic NH4+ with multiple cations mimicking digestate solution, supernatant of digestate with small organic particles and dissolved organic matter, and digestate mixture containing supernatant and large organic particles. The results showed that compared with pure NH4+ solution, the adsorbed NH4+ was 42% lower in the synthetic NH4+ solution with multiple cations but was 2.2 time higher in the supernatant of digestate on two biochars following 48-h adsorption. Modified biochar did not change NH4+ adsorption in pure NH4+ solution despite higher specific surface area than raw biochar, but it increased the adsorption of NH4+ in digestate solutions with high pH (e.g., 4.03 vs. 3.37 mg N g−1 for modified and raw biochar, respectively, in the supernatant of digestate). Compared with the supernatant, the large organic particles in digestate mixture significantly but slightly decreased NH4+ adsorption on ...