Hexavalent chromium (Cr(VI)) in groundwater impose serious health problems for human society. This study investigates the potential of using calcium (Ca) bentonite amended with sodium hexametaphosphate (SHMP) as a backfill constituent material in the soil-bentonite slurry trench wall to envelop the Cr(VI) impacted groundwater. The hydraulic conductivity (K) and consolidation of backfill comprising of 80 wt% sand and 20 wt% SHMP-amended Ca-bentonite were determined via flexible-wall permeameter tests and oedometer tests, respectively. Microstructure characterizations of the amended bentonites before and after contamination were also explored. The results indicated that when the permeated liquid changed from tap water to Cr(VI) solution, the tested specimens exhibited a 1.0 to 1.2-fold variation in short-term K, with all K values fall in range of 2.1 × 10⁻¹⁰ to 2.5 × 10⁻¹⁰ m/s. This mild variation may be attributed to terminate the tests without achieving chemical equilibrium. On the other hand, the Cr(VI) solution had insignificant effect on consolidation of the amended backfill, which is attributed to the dominated incompressible sand matrix skeleton in the backfill that withstood the consolidation pressure and shield the negative effects of the contaminated solution. The microstructure images revealed that the Cr(VI) resulted in relatively strong interlink between particles. Overall, the SHMP-amended bentonite is promising for enhancing Cr(VI) containment performance of the soil-bentonite slurry trench wall backfills.

地下水中的六价铬 (Cr(VI)) 给人类社会带来严重的健康问题。本研究调查了使用六偏磷酸钠 (SHMP) 改性的钙 (Ca) 膨润土作为土壤-膨润土浆液沟壁中的回填成分材料来包裹受 Cr(VI) 影响的地下水的潜力。由 80 wt% 砂和 20 wt% SHMP 改性钙膨润土组成的回填土的水力传导率 ( K ) 和固结度是通过柔性壁渗透仪测试确定的，并且oedometer 测试，分别。还研究了污染前后改性膨润土的微观结构特征。结果表明，当渗透液从自来水改变为铬（VI）溶液中，测试的试样表现出短期的一个1.0至1.2倍的变化ķ，与所有ķ值落入在范围为2.1×10 ^-10至2.5 × 10 ⁻¹⁰ 多发性硬化症。这种轻微的变化可归因于在未达到化学平衡的情况下终止测试。另一方面，Cr(VI)溶液对改良回填土的固结作用不显着，这是由于回填土中占主导地位的不可压缩砂基质骨架承受了固结压力并屏蔽了污染溶液的负面影响。微观结构图像显示 Cr(VI) 导致颗粒之间相对较强的互连。总体而言，经过 SHMP 改性的膨润土有望提高土壤膨润土泥浆沟壁回填物的 Cr(VI) 围堵性能。