Liu Dengfeng, Ren Liming, Wen Chunyu, Dong Jun
a Key Laboratory of Groundwater Resources and Environment, Ministry of Education , Jilin University , Changchun , People's Republic of China.
Environ Technol. 2018 Mar;39(5):607-615. doi: 10.1080/09593330.2017.1309073. Epub 2017 Apr 5.
Shear thinning xanthan gum (XG) solutions as the delivery media can solve the bypassing problem induced by heterogeneity, especially with low permeable zones in aquifers. Experiments were conducted to investigate the compatibility of XG and calcium polysulfide (CPS) aiming at chromium contamination in groundwater. Rheological properties of XG solutions DURING delivery were studied. Results indicated that (1) XG slowed down the reduction of hexavalent chromium by CPS, and the reaction fitted well with the second-order kinetics. (2) CPS dosage had a significant effect on the removal of chromium (VI), but it was less pronounced as the CPS concentration over 160 mg/L. (3) Cationic ions (e.g. Na and Ca) decreased the solution viscosity, while anionic ions maintained the viscosity and shear thinning properties of XG solutions. CPS decreased the viscosity of XG solutions. (4) The solution viscosity increased linearly with the XG concentration (less than 1500 mg/L) at a low shear rate. The presence of aquifer media resulted in a drastic decrease in solution viscosity due to physical molecular breakdown and biodegradation. (5) The rheological properties of XG solutions were described by a power law model. The presented empirical relations may also provide a theoretical basis for field applications.
作为输送介质的剪切变稀黄原胶（XG）溶液可以解决由非均质性引起的绕过问题，特别是在含水层中存在低渗透区的情况下。针对地下水中的铬污染，开展了研究XG与多硫化钙（CPS）相容性的实验。研究了XG溶液在输送过程中的流变特性。结果表明：（1）XG减缓了CPS对六价铬的还原作用，且该反应符合二级动力学。（2）CPS投加量对铬（VI）的去除有显著影响，但当CPS浓度超过160mg/L时，这种影响不太明显。（3）阳离子（如Na和Ca）会降低溶液粘度，而阴离子则能保持XG溶液的粘度和剪切变稀特性。CPS会降低XG溶液的粘度。（4）在低剪切速率下，溶液粘度随XG浓度（小于1500mg/L）呈线性增加。含水层介质的存在会因物理分子分解和生物降解导致溶液粘度急剧下降。（5）XG溶液的流变特性可用幂律模型描述。所给出的经验关系也可为现场应用提供理论依据。
