Department of Chemical Engineering, University of Patras, GR-26504 Patras, Greece.
J Colloid Interface Sci. 2011 Nov 1;363(1):145-56. doi: 10.1016/j.jcis.2011.07.048. Epub 2011 Jul 27.
A new method for the consolidation of loose sand formations has been developed. The method involves in situ precipitation of a composite calcium phosphate-polyelectrolyte salt that binds together with loose sand grains, thus resulting to their consolidation. Three different polyelectrolytes (PE) were tested, i.e., polyacrylic acid (PAA), polyallylamine hydrochloride (PAH), and polyethylenimine (PEI). The effect of PE tested on the thermodynamics and the kinetics of precipitation of calcium phosphate salts was investigated. Three types of experiments were done. Investigation of the adsorption of PE on either hydroxyapatite (Ca(5)(PO(4))(3)OH, HAP) crystals or on sand grains. Measurement of the kinetics of heterogeneous nucleation of HAP on the solid substrates and the mechanical properties of the obtained crystals in batch experiments of low and high supersaturation solutions, respectively. Evaluation of the consolidation in sand packs in order to investigate the effectiveness of the method. The crystallization rates, R(p), on HAP crystals in the presence of the PE tested were found in the order R(p)(PAA)>R(p)(PEI)>R(p)(PAH), while nucleation and crystal growth on silicate sand took place only in the absence of adsorbed PE. PAH favored strongly the consolidation process, whereas PEI and PAA resulted in the formation of poorly consolidated grain agglomerates.
一种用于固结疏松砂层的新方法已经开发出来。该方法涉及原位沉淀复合磷酸钙-聚电解质盐，该盐与松散的砂粒结合，从而使砂粒固结。测试了三种不同的聚电解质（PE），即聚丙烯酸（PAA）、盐酸聚烯丙胺（PAH）和聚乙烯亚胺（PEI）。研究了 PE 对磷酸钙盐沉淀的热力学和动力学的影响。进行了三种类型的实验。研究了 PE 在羟基磷灰石（Ca(5)(PO(4))(3)OH，HAP）晶体或砂粒上的吸附。分别在低过饱和度和高过饱和度溶液的批实验中，测量了 HAP 在固体基质上异质成核的动力学和获得的晶体的机械性能。评估了在砂包中的固结情况，以研究该方法的有效性。在测试的 PE 存在下，HAP 晶体上的结晶速率 R(p)的顺序为 R(p)(PAA)>R(p)(PEI)>R(p)(PAH)，而在没有吸附的 PE 的情况下，硅酸盐砂上发生了成核和晶体生长。PAH 强烈促进固结过程，而 PEI 和 PAA 导致形成固结不良的颗粒团聚体。
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