Preparation of Magnetic Excess Sludge and Removal of Phosphate

doi:10.13209/j.0479-8023.2017.107

Abstract

Abstract:

MNPs were prepared using coprecipitation method, with FeCl₃, FeCl₂ and ammonia. MNPs were compounded with excess sludge (moisture content of 99%) to prepare magnetic excess sludge (MES). Alternating gradient magnetometer was used to measure the magnetic response of MES and scanning electron microscope (SEM) to observe morphology of excess sludge and MES. After magnetic separation, the water content of MES was calculated to investigate the degree of sludge thickening. The adsorption property of total phosphorus onto MES was investigated. According to the results, MES had superparamagnetism, and its saturation magnetization was 42 emu/g. Within 30 s it could be separated from liquid. The optimal conditions for adsorption of total phosphorus on MES were the initial pH value of solution ranging in 4-6, an initial concentration of phosphorus solution of 16 mg/L (calculated as P), adsorption equilibrium was achieved within 600 min. The kinetics data were fitted well with the pseudo-second order model. The adsorption fitted the Langmuir isotherm well with the equilibrium data and the theoretical maximum adsorption capacity was 3.00 mg/g (calculated as P). MES could accelerate the separation of sludge and wastewater, and the volume of excess sludge was reduced largely. The adsorption performance of total phosphorus on MES was better than that on excess sludge. The study provided a new handling method of excess sludge for sewage treatment plant whose secondary treatment process was activated sludge process.

Key words: magnetic excess sludge, magnetic separation, adsorption, phosphate

摘要：

以FeCl₃, FeCl₂和NH₃·H₂O为原料, 通过共沉淀法制备磁性Fe₃O₄纳米颗粒(MNPs), 并将含水率为99%的剩余污泥与其复合, 制备磁性剩余污泥(MES)。采用交变梯度磁强计测定、扫描电子显微镜观察等分析方法对MES进行表征。计算磁分离后的污泥体积浓缩程度, 进行MES对磷的吸附去除研究。结果表明, MES具有超顺磁性, 其饱和磁化强度为42 emu/g, 30秒内可实现固液分离, 且分离后的MES体积为原剩余污泥体积的1/10。MES吸附磷的最适pH为4~6, 最佳磷溶液初始浓度为16 mg/L (以P计), 600分钟后达到吸附平衡。准二级动力学模型对吸附试验数据的拟合程度较高。MES对磷的吸附等温线符合Langmuir方程, 理论最大吸附量为3.00 mg/g (以P计)。磁性剩余污泥可快速、大幅度地缩减剩余污泥体积, 且对磷的吸附性能优于剩余污泥。研究结果可为处理剩余污泥提供新的途径。

关键词: 磁性剩余污泥, 磁分离, 吸附, 磷

Huchun TAO, Xiao ZHANG, Jinbo LI, Shuaibin HUANG, Biao MA. Preparation of Magnetic Excess Sludge and Removal of Phosphate[J]. Acta Scientiarum Naturalium Universitatis Pekinensis, 2017, 53(6): 1108-1114.

陶虎春, 张晓, 李金波, 黄帅斌, 马骉. 一种磁性剩余污泥的制备及其除磷研究[J]. 北京大学学报自然科学版, 2017, 53(6): 1108-1114.

Figures/Tables 10

Fig. 1 Effects of mixture ratio and compounding time of MNPs and activated sludge on magnetic response of MES

Fig. 2 SEM of excess sludge and MES

Fig. 3 Magnetic separation of MES

Fig. 4 Adsorption properties of total phosphorus onto excess sludge, MNPs and MES

Fig. 5 Effect of pH on adsorption of total phosphorus on MES

Fig. 6 Effect of initial concentration on adsorption of total phosphorus on MES

Fig. 7 Effect of contact time on adsorption of total phosphorus on MES

Table 1 Kinetic parameters of total phosphorus adsorption on MES

模型	方程	参数	数值
准一级动力学模型	${{q}_{t}}={{q}_{\text{e}}}(1-{{\text{e}}^{(-{{k}_{1}}t)}})$	k₁	0.0263
		q_e	1.46
		R²	0.900
准二级动力学模型	${{q}_{t}}=\frac{q_{\text{e}}^{2}{{k}_{2}}t}{1+{{q}_{\text{e}}}{{k}_{2}}t}$	k₂	0.0232
		q_e	1.58
		R²	0.964

Table 2 Isotherm parameters of total phosphorus on MES

模型	参数	数值
Langmuir	q_m	3.00
	b	0.765
	R²	0.974
Freundlich	K_f	1.26
	n	2.61
	R²	0.864

Fig. 8 Adsorption isotherms of total phosphorus on MES

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