Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA.
Department of Civil Engineering, Texas A&M University, College Station, TX 77843-3136, USA; Department of Chemical Engineering, Texas A&M University, College Station, TX 77843-3122, USA.
Water Res. 2017 Dec 1;126:481-487. doi: 10.1016/j.watres.2017.09.057. Epub 2017 Sep 28.
One promising water management strategy during hydraulic fracturing is treatment and reuse of flowback/produced water. In particular, the saline flowback water contains many of the chemicals employed for fracking, which need to be removed before possible reuse as "frac water." This manuscript targets turbidity along with one of the additives; borate-based cross-linkers used to adjust the rheological characteristics of the frac-fluid. Alum and ferric chloride were evaluated as coagulants for clarification and boron removal from saline flowback water obtained from a well in the Eagle Ford shale. Extremely high dosages (> 9000 mg/L or 333 mM Al and 160 mM Fe) corresponding to Al/B and Fe/B mass ratios of ∼70 and molar ratios of ∼28 and 13 respectively were necessary to remove ∼80% boron. Hence, coagulation does not appear to be feasible for boron removal from high-strength waste streams. X-ray photoelectron spectroscopy revealed BO bonding on surfaces of freshly precipitated Al(OH)(am) and Fe(OH)(am) suggesting boron uptake was predominantly via ligand exchange. Attenuated total reflection-Fourier transform infrared spectroscopy provided direct evidence of inner-sphere boron complexation with surface hydroxyl groups on both amorphous aluminum and iron hydroxides. Only trigonal boron was detected on aluminum flocs since possible presence of tetrahedral boron was masked by severe AlO interferences. Both trigonal and tetrahedral conformation of boron complexes were identified on Fe(OH) surfaces.
在水力压裂过程中，一种有前景的水管理策略是处理和再利用返排/产出水。特别是，含盐水返排水中含有许多用于压裂的化学物质，在可能作为“压裂水”再利用之前，这些化学物质需要被去除。本文针对浊度以及其中一种添加剂进行了研究；硼酸盐基交联剂用于调节压裂液的流变性。使用硫酸铝和氯化铁作为混凝剂，从鹰福特页岩中的一口井中获得的含盐水返排水中进行澄清和除硼。为了去除约 80%的硼，需要极高的剂量 (> 9000 mg/L 或 333 mM Al 和 160 mM Fe)，相应的 Al/B 和 Fe/B 质量比约为 70，摩尔比分别约为 28 和 13。因此，混凝似乎不适用于从高强度废水中去除硼。X 射线光电子能谱显示，在新沉淀的 Al(OH)(am)和 Fe(OH)(am)表面存在 BO 键合，表明硼的摄取主要是通过配体交换。衰减全反射-傅里叶变换红外光谱提供了直接证据，表明无定形铝和铁氢氧化物表面上的内球硼络合物与表面羟基配位。由于 AlO 干扰严重，仅在铝絮体上检测到三角硼，因为可能存在四面体硼。在 Fe(OH)表面上都检测到了硼配合物的三角和四面体构象。
