Pilot process of arsenic-containing groundwater purification by iron-based granular adsorbent fixed bed column
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摘要:
以农村地区的As污染地下水为处理对象，研发了同步去除水中As(Ⅲ)和As(Ⅴ)的铁基颗粒吸附剂（FMGA），设计并建立了以吸附固定床为核心单元的中试除As装置，对As污染地下水的处理效果进行研究。结果表明：在33 d的连续运行过程中，除As装置出水As浓度始终低于GB 5749—2022《生活饮用水卫生标准》规定限值（10 μg/L），吸附固定床首次运行的穿透时间达到786 h；使用0.2 mol/L的NaOH溶液对吸附剂进行原位再生后，吸附固定床再次运行的穿透时间仍可达到750 h，其除As性能的恢复率接近91%；除As装置的出水浊度接近于0，Fe、Mn离子浓度均低于GB 5749—2022的限值（Fe浓度为0.3 mg/L，Mn浓度为0.1 mg/L），FMGA可高效再生回用且无二次污染。吸附动力学表明，FMGA吸附As的过程符合准二级动力学模型，As通过化学吸附被去除；吸附等温线表明，FMGA对As的理论最大吸附容量为74.94 mg/g（pH为7.0）。通过表征研究可知，FMGA最大荷载为89.39 N，具有出色的机械强度。
Abstract:Arsenic (As) pollution in groundwater has become an important environmental issue in China. In order to purify the arsenic-contaminated groundwater in rural areas, an iron-based granular adsorbent (FMGA) capable of synchronously removing As(Ⅲ) and As(Ⅴ) from water was developed and packed into an adsorption fixed bed. A pilot-scale water treatment system was designed and established with a fixed bed as the core unit, which had a good capability for the treatment of As-contaminated groundwater. The results showed that during the continuous operation of 33 days, the residual As concentration in the effluent of the pilot-scale system was continuously below the limit of Standards for Drinking Water Quality (GB 5749-2022 ) (10 μg/L). The breakthrough time of the fixed bed reached 786 h in the first cycle. After the in-situ regeneration using 0.2 mol/L NaOH solution, the breakthrough time of the fixed bed for reuse could still reach 750 h, and the recovery rate of its arsenic adsorption capacity was close to 91%. The turbidity of the effluent for the pilot-scale system was close to zero, and the concentrations of iron and manganese ions were both lower than the limits of the sanitary standard (Fe<0.3 mg/L, Mn<0.1 mg/L). FMGA could be efficiently regenerated and reused without secondary pollution. The adsorption kinetics indicated that the adsorption process of As by FMGA was consistent with the quasi-second-order kinetic model, and As could be removed by chemisorption. The adsorption isotherm showed that the theoretical maximum adsorption capacity of FMGA for As was 74.94 mg/g (pH=7.0). According to the surface characterization results, the maximum load of FMGA was 89.39 N, indicating an excellent mechanical strength.
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Key words:
- arsenic (As) /
- groundwater /
- fixed bed /
- Fe-Mn composite oxide /
- granular adsorbent /
- pilot-scale experiment
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图 1 中试装置除As工艺流程
注：图中数字的单位为mm。
Figure 1. Arsenic removal process flow chart of pilot plant
图 2 FMGA吸附剂的XPS全谱图、机械强度及SEM表征图
Figure 2. XPS full spectrum, mechanical strength, and SEM characterization of FMGA adsorbent
图 3 FMGA吸附As(Ⅲ)过程中的动力学模型拟合以及溶液中残余的As(Ⅲ)、As(Ⅴ)浓度变化
Figure 3. Fitting of kinetic models and concentration changes of As (Ⅲ) and As (Ⅴ) in FMGA adsorption process
图 4 FMGA对As(Ⅲ)的吸附等温线（Langmuir和Freundlich模型拟合）
Figure 4. Adsorption isotherm of As(Ⅲ) on the FMGA (Model fitting of Langmuir and Freundlich)
图 5 中试系统出水的As(tot)、As(Ⅲ)及As(Ⅴ)浓度变化
注：As浓度限值指GB 5749—2022中As浓度限值（10 μg/L)。
Figure 5. Changes in As (tot), As(Ⅲ), and As(V) concentrations in the effluent of the pilot system
图 6 中试系统出水pH、浊度、Fe及Mn离子浓度
注：浓度限值分别指GB 5749—2022中Fe浓度限值（0.3 mg/L)、Mn浓度限值（0.1 mg/L)、浊度限值（1.0 NTU)。
Figure 6. PH, turbidity, Fe and Mn ion concentration of effluent from the pilot system
图 7 固定床反应器的As解吸曲线及清洗出水pH变化
Figure 7. Desorption curve of effluent As in fixed bed reactor and change of pH in cleaning effluent
表 1 准一级和准二级动力学模型拟合参数
Table 1. The pseudo-first order and pseudo-second order models parameters
准一级动力学模型 准二级动力学模型 qe/(μg/g) k1/h−1 R2 qe/(μg/g) k2/〔g/(μg·h)〕 R2 94.12 0.33 0.979 95.24 4.52 0.999 
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表 2 颗粒内扩散模型拟合参数
Table 2. Intra-particle diffusion fitting parameters
外扩散阶段 内扩散阶段 吸附反应阶段 kp/〔μg/(g·h1/2)〕 C/(μg/g) R2 kp/〔μg/(g·h1/2)〕 C/(μg/g) R2 kp/〔μg/(g·h1/2)〕 C/(μg/g) R2 2.89 85.64 0.955 6.06 77.25 0.972 1.19 89.95 0.920
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表 3 Langmuir和Freundlich模型拟合参数
Table 3. Langmuir and Freundlich model fitting parameters
Freundlich模型 Langmuir模型 KF/〔(mg/g)/(mg/L)n〕 1/n R2 qmax/(mg/g) KL/(L/mg) R2 5.38 1.13 0.991 74.94 0.02 0.987
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表 5 Thomas模型拟合固定床反应器穿透曲线参数
Table 5. Thomas model fitting fixed bed reactor breakthrough curve parameters
运行周期 t/(min) Q/(L/h) C0/(μg/L) Thomas模型参数 kTh×10−6/〔mL/(min·μg)〕 q0/(mg/g) R2 第一周期 47 160 500 45 7.03 284.8 0.94 第二周期 45 000 500 45 6.44 276.3 0.97
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表 6 FMGA与市场中相关的除As吸附剂价格对比
Table 6. Comparison of prices between FMGA and market related As removal adsorbents
吸附剂名称 价格/（元/kg） 生产厂家 FMGA 33.4 本研究 GEH® 80 德国沃驰公司（Watch® Water） FERROLOX-X 80 德国沃驰公司（Watch® Water） TITANSORBTM 120 德国沃驰公司（Watch® Water） KATALOX-LIGHT 40 德国沃驰公司（Watch® Water） Trppsorb & Crystolite 95 德国沃驰公司（Watch® Water） BAYOXIDE® E33 175 德国拜耳公司
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