The influence of organic matter on mineral surface area measurement of mudrocks by ethylene glycol monoethyl ether adsorption

Abstract

Mineral surface is a pivotal place for interactions between minerals and other materials and is helpful to be quantitatively characterized with the aid of measuring the mineral surface area (MSA) by ethylene glycol monoethyl ether (EGME) adsorption. However, in fine-grained sediments, the existence of organic matter (OM) may impede the accuracy of their EGME MSA measurement. This study selected mudrocks with type-I and type-III OM and separated their OMs, which were subjected to total organic carbon content (TOC) and EGME adsorption measurement to investigate the influence of OM on MSA measurement of mudrock by EGME adsorption. The results show that OM has a remarkable contribution to EGME specific surface area (EGME SSA) of mudrocks, and the contribution from type-I OM is greater than type-III OM. The contribution rate of OM to EGME SSA of mudrocks is exponentially correlated with TOC and EGME SSA of mudrocks, indicating that different influential extents of OM to EGME MSA of mudrocks depend on its TOC and EGME retention capacity. By mathematical extrapolation, mudrocks with TOC < 1.5 wt% or EGME SSA > 100 m2/g is recommended to be available for EGME adsorption to measure MSA of mudrock. Otherwise, OM removal of mudrock sample has to be performed prior to employing EGME adsorption. This study discusses the contribution of OM to EGME SSA of mudrocks and provides two measures to judge the validity of EGME adsorption for MSA measurement of mudrocks, which is helpful to sample preparation for EGME adsorption and identify the availability of EGME MSA.