It is widely accepted that the zeta potential in natural sandstones is negative in the brine pH and compositions found in the subsurface. The zeta potential is a measure of the electrical potential at a mineral surface. We report new measurements of the zeta potential using a saline natural brine rich in divalent ions. The sandstones samples were quartz-dominated but some also contained dolomite, siderite and clay minerals. The quartz-dominated sandstones showed behaviour consistent with earlier studies, but the dolomite- and siderite-bearing samples returned positive zeta potentials. We suggest that this is caused by a positive zeta potential on dolomite and siderite mineral surfaces, adsorption of divalent ions onto quartz mineral surfaces and/or ion exchange with clay minerals. The results have broad implications for the zeta potential of natural sandstones, because the magnitude and polarity of the zeta potential impact geophysical monitoring and the transport of the charged contaminants.

中文翻译：

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天然盐水饱和砂岩中的正 Zeta 电位

人们普遍认为，天然砂岩中的 zeta 电位在盐水 pH 值和地下发现的成分中为负值。zeta 电位是矿物表面电位的量度。我们报告了使用富含二价离子的盐水天然盐水对 zeta 电位的新测量。砂岩样品以石英为主，但有些还含有白云石、菱铁矿和粘土矿物。以石英为主的砂岩表现出与早期研究一致的行为，但含白云石和菱铁矿的样品返回了正 zeta 电位。我们认为这是由白云石和菱铁矿矿物表面的正 zeta 电位、二价离子吸附到石英矿物表面和/或与粘土矿物的离子交换引起的。