Comprehensive screening and prediction of effective and lasting water purification and phosphorus removal substrates
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摘要: 为筛选效果好且长效的除磷基质,选取电气石陶粒、赤泥陶粒、凹凸棒石、硅胶、海绵铁、活性炭、火山岩、沸石8种基质进行磷静态吸附试验,优选3种基质进行单基质柱状除磷渗流试验和微观结构表征,获取基质的除磷特征,并依据渗流试验数据建模预测长效除磷效果。结果表明:8种基质对磷的吸附能力差异较大,其中电气石陶粒、赤泥陶粒、沸石吸附能力较好;渗流试验中,电气石陶粒在111 d后对磷的去除率仍维持在67%,赤泥陶粒则降至37%;不同基质出水总磷浓度随时间呈现不同变化规律,其统计模型预测性较好,经建模预测得出,电气石陶粒在第160天左右对磷的去除率降至50%,第300天左右达到吸附饱和,赤泥陶粒则在第150天左右达到吸附饱和。基质微观结构(比表面积、表面特征)及化学元素组成等对除磷效果有明显影响。Abstract: In order to select effective and lasting phosphorus removal substrates, eight kinds of substrates, including tourmaline ceramsite, red mud ceramsite, attapulgite, silica gel, sponge iron, activated carbon, volcanic rock and zeolite, were taken for phosphorus static adsorption experiments. Three substrates were selected for single-substrate columnar phosphorus removal percolation experiment and microstructure characterization, to obtain the phosphorus removal characteristics of each substrate, and to predict their long-term phosphorus removal effect by modeling based on percolation experimental data. The investigation results showed that the adsorption capacities of the eight substrates for phosphorus were quite different, the top three of which were tourmaline ceramsite, red clay ceramsite, and zeolite in order. In the seepage experiment, the phosphorus removal rate of tourmaline ceramsite remained at 67% after 111 days, while that of red mud ceramsite dropped to 37%. The total phosphorus concentration of effluent from different substrates presented differently over time, and the pertinent statistical models showed good predictability. It was predicted by the models that the phosphorus removal rate of tourmaline ceramsite would drop to 50% in about 160 days, and the adsorption saturation would be reached in about 300 days. In comparison, the red mud ceramsite would be saturated on adsorption in about 150 days. The microstructure of the substrates, including their specific surface area and surface characteristics, and their chemical element composition had a significant effect on the removal rate.
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表 1 3种基质等温吸附拟合参数
Table 1. Three substrates isotherm adsorption fitting parameters
基质 Langmuir模型 Freundlich模型 qmax/(mg/g) KL/(L/mg) R2 KF/(mg/g) 1/n R2 电气石陶粒 0.669 0.085 0.927 0.112 0.409 0.959 赤泥陶粒 0.571 0.016 0.981 0.019 0.660 0.978 沸石 0.642 0.008 0.969 0.008 0.782 0.951 表 2 3种基质在
${C}_{\mathrm{e}}$ 小于30 mg/L的线性拟合参数Table 2. Linear fitting parameters of three substrates at Ce less than 30 mg/L
基质 Kd R2 电气石陶粒 0.035 6 0.957 赤泥陶粒 0.007 0 0.983 沸石 0.002 6 0.972 表 3 3种基质不同时段试验数据的拟合及其预测精度对比
Table 3. Comparing the fitting and prediction accuracy of the experimental data of 3 kinds of substrates in different periods
基质 试验时段/d 拟合方程 R2 均方根误差 平均绝对百分比误差/% 0~30 y=0.043 32x 0.995 0.7 23 赤泥陶粒 0~62 y=0.037 7x 0.979 0.5 14 0~111 y=0.034x 0.980 0~30 y=0.496ln(x−0.898)+3.4 0.900 0.5 7.5 沸石 0~62 y=0.37ln(x−0.98)+3.66 0.840 0.3 4.4 0~99 y=0.316ln(x−0.99)+3.789 0.811 电气石陶粒 0~30 y= 0.000 724x (最佳拟合) 0.417 0.7 169 电气石陶粒(多项式) 0~62 y=0.000 316x2−0.011x+0.08 0.935 0.7 50 电气石陶粒(多项式) 34~62 y=0.000 487x2−0.024 1x+0.283 0.934 1.13 81 电气石陶粒(线性) 34~62 y=0.022 43x−0.787 0.909 0.27 21 电气石陶粒(多项式) 0~111 y=0.000 119x2+0.002x−0.05 0.906 电气石陶粒(线性) 34~111 y=0.018 9x−0.587 0.864 表 4 电气石陶粒和赤泥陶粒出水总磷浓度预测
Table 4. Prediction of total phosphorus effluent concentration of tourmaline ceramsite and red mud ceramsite
mg/L 基质 运行时间/d 120 130 140 147 163 250 295 电气石陶粒 1.68 1.87 2.06 2.25 2.50 4.14 5.00 赤泥陶粒 4.08 4.42 4.76 5.00 表 5 3种基质的比表面积、总孔体积及平均孔径
Table 5. Specific surface area, total pore volume and average pore diameter of three substrates
基质 比表面积/(m2/g) 总孔体积/(cm3/g) 平均孔径/nm 电气石陶粒 55.50 0.052 2 3.763 赤泥陶粒 60.74 0.079 2 5.215 沸石 23.43 0.065 7 11.21 表 6 基质中主要化学成分及其含量
Table 6. Main chemical components and contents in substrates
% 基质 Al Ca Fe Mg Si K Mn Na 电气石陶粒 7.986 52.976 6.109 4.938 22.196 1.753 0.273 0.674 赤泥陶粒 17.570 5.901 7.934 0.946 54.664 8.675 0.177 2.127 -
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