摘要
鸟粪石结晶沉淀法回收剩余污泥中磷工艺具有良好的应用前景,但污泥中有机物,特别是大量的胞外聚合物(EPS),易吸附到鸟粪石表面对其结晶过程产生一定的影响,而pH是影响其吸附性能的关键因素.由于海藻酸化学性质与EPS相似,以海藻酸作为EPS替代物,在弱碱性条件(7.5≤pH≤11)下开展鸟粪石吸附海藻酸实验.利用自动电位滴定仪对鸟粪石进行表面酸碱滴定,借助恒电容模型计算其表面酸碱平衡常数;同时采用三层模型对吸附数据进行模拟计算,探讨pH影响鸟粪石吸附海藻酸的机制.结果表明,鸟粪石表面吸、脱附质子常数分别为7.6和-10.6,表面位密度为12个·nm^(-2);在离子强度为0.1 mol·L^(-1)NaCl条件下pH的增大抑制鸟粪石对海藻酸的吸附;鸟粪石对海藻酸吸附机理主要通过外层络合及内层络合协同作用,其中外层络合作用始终占主导优势.
Phosphorus recovery from excess activated sludge by the crystallization of struvite has a good application prospect. However, organic substances in the sludge, especially a considerable amount of extracellular polymers （EPS） , have a certain impact on the crystallization of struvite via the adsorption on the surface of struvite crystals. Furthermore, the solution pH is a key point affecting the adsorption of organics on struvite. Being similar to EPS in chemical property, alginic acid was applied as a substitute of EPS to investigate the adsorption of EPS over the surface of struvite crystals under weak alkaline conditions （7.5 ≤ pH ≤11 ）. Acid-base titration of synthetic struvite was performed by automatic potentiometric titration followed by the calculation of surface equilibrium constants of acid-base in virtue of constant capacitance model （CCM） based on the titration data. To explore the mechanism of the adsorption under different pH conditions, the adsorption data was fitted by a Triple Layer Model （TLM）. The results indicate that an increase of solution pH from 7.5 to 11 hampered the adsorption of alginic acid on struvite crystals in the presence of ion strength 0.1 mol·L-1 NaCl. According to the CCM, the protonation and deprotonation equilibrium constant of struvite crystal surface calculated are determined to be 7.6 and -10.6, respectively, with a surface site density of 12 sites, nm-2. It was proved that the inner- and the outer-sphere complex were involved in the adsorption process of alginic acid on struvite crystals, where the outer-sphere complex dominated the adsorption.
出处
《环境科学学报》
CAS
CSCD
北大核心
2017年第9期3364-3369,共6页
Acta Scientiae Circumstantiae
基金
国家自然科学基金(No.41130206)~~
