Hakim Azizul, Suzuki Tomoharu, Kobayashi Motoyoshi
Graduate School of Life and Environmental Sciences and Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba 305-8572, Ibaraki, Japan.
Department of Soil Science, University of Chittagong, Chittagong 4331, Bangladesh.
ACS Omega. 2019 May 15;4(5):8559-8567. doi: 10.1021/acsomega.9b00124. eCollection 2019 May 31.
Aggregation-dispersion, charging, and aggregate strength of Leonardite humic acid (LHA) were investigated in CaCl and MgCl solutions as a function of pH and ionic strength (). The strength or the withstanding force of aggregates of humic substances (HSs) against breakage is important because this force influences the transport and distribution of pollutants and nutrients along with HSs through the change in the size of HS aggregates as a transport unit. We observed the dominancy of aggregation of LHA at high pH than at low pH in every case of CaCl and MgCl solutions. This observation suggests the higher binding efficiency of these divalent ions at high pH, though there was no obvious relation with electrophoretic mobility and aggregation of LHA. Further, we first revealed the numerical value of the strength of HS aggregates by using a simple experimental setup of aggregate breakup under laminar converging flow through a capillary tube. The obtained values of the strength of LHA aggregates were higher in the presence of CaCl solution than MgCl solution, and the strength increased with pH. The highest strengths of LHA aggregates in 30 mM () CaCl and MgCl solutions were around 5.8 and 2.4 nN, respectively, at pH around 9.
研究了在氯化钙（CaCl）和氯化镁（MgCl）溶液中，作为pH值和离子强度（）函数的风化煤腐殖酸（LHA）的聚集-分散、带电情况及聚集体强度。腐殖物质（HSs）聚集体的强度或抗破碎力很重要，因为该力会随着作为运输单元的HS聚集体大小的变化，影响污染物和养分随HSs的迁移和分布。在氯化钙和氯化镁溶液的每种情况下，我们都观察到在高pH值时LHA的聚集比在低pH值时更占主导。这一观察结果表明，在高pH值时这些二价离子具有更高的结合效率，尽管LHA的电泳迁移率和聚集没有明显关系。此外，我们首次通过使用一种简单的实验装置，即通过毛细管在层流汇聚流下使聚集体破碎，揭示了HS聚集体强度的数值。在氯化钙溶液存在下，LHA聚集体的强度值高于氯化镁溶液，且强度随pH值增加。在pH值约为9时，30 mM（）氯化钙和氯化镁溶液中LHA聚集体的最高强度分别约为5.8和2.4 nN。
