Hilbrandt Inga, Lehmann Vito, Zietzschmann Frederik, Ruhl Aki Sebastian, Jekel Martin
Technische Universität Berlin, Chair of Water Quality Control Str. des 17. Juni 135 10623 Berlin Germany
TU Delft, Water Management Stevinweg 1 2628 CN Delft Netherlands.
RSC Adv. 2019 Jul 30;9(41):23642-23651. doi: 10.1039/c9ra04865k. eCollection 2019 Jul 29.
Adsorption onto ferric hydroxide is a known method to reach very low residual phosphate concentrations. Silicate is omnipresent in surface and industrial waters and reduces the adsorption capacity of ferric hydroxides. The present article focusses on the influences of silicate concentration and contact time on the adsorption of phosphate to a micro-sized iron hydroxide adsorbent (μGFH) and fits adsorption data to multi-component adsorption isotherms. In Berlin drinking water (DOC of approx. 4 mg L) at pH 7.0, loadings of 24 mg g P (with 3 mg L initial PO -P) and 17 mg L Si (with 9 mg L initial Si) were reached. In deionized water, phosphate shows a high percentage of reversible bonds to μGFH while silicate adsorption is not reversible probably due to polymerization. Depending on the initial silicate concentration, phosphate loadings are reduced by 27, 33 and 47% (for equilibrium concentrations of 1.5 mg L) for 9, 14 and 22 mg L Si respectively. Out of eight tested multi-component adsorption models, the Extended Freundlich Model Isotherm (EFMI) describes the simultaneous adsorption of phosphate and silicate best. Thus, providing the means to predict and control phosphate removal. Longer contact times of the adsorbent with silicate prior to addition of phosphate reduce phosphate adsorption significantly. Compared to 7 days of contact with silicate ( = 10 mg L) prior to phosphate ( = 3 mg L) addition, 28 and 56 days reduce the μGFH capacity for phosphate by 21 and 43%, respectively.
吸附到氢氧化铁上是一种可达到极低残余磷酸盐浓度的已知方法。硅酸盐在地表水和工业用水中普遍存在，会降低氢氧化铁的吸附能力。本文重点研究了硅酸盐浓度和接触时间对磷酸盐在微米级氢氧化铁吸附剂（μGFH）上吸附的影响，并将吸附数据拟合到多组分吸附等温线。在柏林饮用水（DOC约为4 mg/L）中，pH值为7.0时，达到了24 mg/g P（初始PO₄-P为3 mg/L）和17 mg/L Si（初始Si为9 mg/L）的负载量。在去离子水中，磷酸盐与μGFH形成的可逆键比例较高，而硅酸盐的吸附可能由于聚合作用而不可逆。根据初始硅酸盐浓度的不同，对于1.5 mg/L的平衡浓度，当Si分别为9、14和22 mg/L时，磷酸盐负载量分别降低27%、33%和47%。在八个测试的多组分吸附模型中，扩展弗伦德利希模型等温线（EFMI）对磷酸盐和硅酸盐的同时吸附描述得最好。因此，提供了预测和控制磷酸盐去除的方法。在添加磷酸盐之前，吸附剂与硅酸盐的接触时间延长会显著降低磷酸盐的吸附。与在添加磷酸盐（3 mg/L）之前与硅酸盐（10 mg/L）接触7天相比，接触28天和56天会使μGFH对磷酸盐的吸附容量分别降低21%和43%。
