Ran Xiao1,2, Han Zhang3, Zhineng Tu3, Ronghua Li3, Songling Li4, Zhongyang Xu4, Zengqiang Zhang5. 1. Interdisciplinary Research Center for Agriculture Green Development in Yangtze River Basin, Southwest University, Chongqing, 400715, China. 2. College of Resources and Environment, Southwest University, Chongqing, 400715, China. 3. College of Natural Resources and Environment, Northwest A&F University, Yangling, 712100, Shaanxi, China. 4. Soil and Fertilizer Institute, Qinghai Academy of Agricultural and Forestry Sciences, Xining, 810016, Qinghai, China. 5. College of Natural Resources and Environment, Northwest A&F University, Yangling, 712100, Shaanxi, China. zhangzq58@126.com.
Abstract
In this study, a novel MgO-biochar composite was generated for nutrient recovery from biogas slurry using magnesium chloride (MgCl2) and ammonia hydroxide (NH3·H2O). Biochar properties, including pH, CEC, pHpzc, magnesium content, surface area, and total pore volume (Vtotal), were evaluated. Moreover, the removal of NH4+ and PO43- in both single and bi-solute system were investigated. Results indicated that NH3·H2O pretreatment and MgO-coating enhanced biochar pH, CEC, and pHpzc. Additionally, there were generally higher surface area and Vtotal in MgAWS550. The maximum adsorption capacities for NH4+ and PO43-, respectively, increased as WS550 (0.555 and 1.57 mg g-1) < MgWS550 (15.4 and 21.8 mg g-1) < MgAWS550 (17.5 and 31.3 mg g-1). Moreover, higher removal efficiencies were achieved in the bi-solute system, and over 25% and 90% of NH4+ and PO43-, respectively, was removed from biogas slurry by MgASW550. Mechanically, NH4+ removal was mainly attributed to ionic exchange, while PO43- adsorption on MgO-coated biochars was due to electrostatic attraction and precipitation. Furthermore, the formation of struvite (MgNH4PO4·6H2O) further enhanced N and P in the bi-solute system.
In this study, a novel n class="Chemical">MgO-biochar composite was genpan>erated for nutrienpan>t recovery from biogas slurry using n class="Chemical">magnesium chloride (MgCl2) and ammonia hydroxide (NH3·H2O). Biochar properties, including pH, CEC, pHpzc, magnesium content, surface area, and total pore volume (Vtotal), were evaluated. Moreover, the removal of NH4+ and PO43- in both single and bi-solute system were investigated. Results indicated that NH3·H2O pretreatment and MgO-coating enhanced biochar pH, CEC, and pHpzc. Additionally, there were generally higher surface area and Vtotal in MgAWS550. The maximum adsorption capacities for NH4+ and PO43-, respectively, increased as WS550 (0.555 and 1.57 mg g-1) < MgWS550 (15.4 and 21.8 mg g-1) < MgAWS550 (17.5 and 31.3 mg g-1). Moreover, higher removal efficiencies were achieved in the bi-solute system, and over 25% and 90% of NH4+ and PO43-, respectively, was removed from biogas slurry by MgASW550. Mechanically, NH4+ removal was mainly attributed to ionic exchange, while PO43- adsorption on MgO-coated biochars was due to electrostatic attraction and precipitation. Furthermore, the formation of struvite (MgNH4PO4·6H2O) further enhanced N and P in the bi-solute system.
Entities:
Keywords:
Ammonia hydroxides hydrolysis; Biogas slurry; Engineered biochar; MgO; N and P recovery; Struvite formation
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