改性黑臭河道沉积物对营养盐去除的研究

Efficiency and mechanism of nutrient removal using modified sediments from a malodorous river

为研究黑臭河道沉积物资源化利用方式,评估沉积物资源化以后对营养盐去除效果和研究其去除机制,以北京市某黑臭河道沉积物(S)为供试样品,对其进行氧化并负载金属离子改性,最终得到氧化-载钠改性沉积物(MS).选取S和MS两种材料,评估其对氮和磷的去除效果,通过采用动力学、热力学等手段,进一步阐明改性材料对氮、磷去除机制.结果表明,在环境温度为35℃,固液比1∶50(g∶ml)的条件下,经氧化-载钠联合改性材料对氮(初始浓度20mg/L)的去除效果均达到90%以上,其中对磷(初始浓度10mg/L)的去除率最高可达98%;准二级动力学模型能更好的描述改性材料的吸附动力学行为(R2>0.93),且动力学和吸附等温分析结果显示,Langmuir模型可以更好地描述两种材料的吸附等温线,改性材料对氮和磷的最大吸附量分别达到0.891和0.474mg/g;热力学研究结果表明,吸附过程中,标准反应焓变(ΔH^0)、标准反应熵变(ΔS^0)均为正值,标准吉布斯自由能变(ΔG^0)为负值,且随着温度的升高,ΔG^0呈下降趋势.研究显示,MS具有更高的吸附性能,对氮、磷的吸附主要是材料表面活性吸附点位起主导作用,并且吸附过程是个吸热、自发进行的过程,更高的温度更有利于吸附.在同一温度下,随着氮、磷初始浓度的增加,MS对氮、磷的解吸比吸附过程更容易发生.

In order to study the method of sediment resource utilization in the malodorous river,and to evaluate the nutrient removal efficiency using modified sediment and its removal mechanism,the sediment samples (S) from a seriously malodorous river in Beijing were collected in this study.The sediment was modified by oxidation and metal ion-loaded (MS).The nutrient removal efficiency for S and MS was evaluated.The removal mechanism of nutrient was studied through kinetics,equilibrium,and thermodynamic experiments.The results indicated that when the environmental temperature was 35℃,and solid to liquid ratio was 1 ∶ 50 ( g ∶ml ),the nitrogen (initial concentration,20 mg/L) and phosphorus (initial concentration,10 mg/L ) removal efficiency by using MS was up to 90 % and 98 %,respectively.The pseudo-second-order model could better describe the sorption kinetics ( R 2 >0.93),and the kinetic and isotherm study illustrated that data from the isotherm experiments were well described by Langmuir isotherm model.The sorption capacity reached 0.891 mg/g for nitrogen and 0.474 mg/g for phosphorus,respectively.The thermodynamic result suggested that enthalpy (Δ H^0 ) and entropy (Δ S^0 ) were positive,and Gibbs energy (Δ G^0 ) was negative during the adsorption experiments.The values of Δ G^0 decreased with the increase of temperature.The results showed that MS had the higher nutrient sorption capacity,and the exterior activated site had the main function of phosphorus and nitrogen sorption.The sorption process was a spontaneous or endothermic reaction,and high temperature was in favour of sorption.In addition,the results also indicated that desorption occurred more easily than sorption at the same temperature.