Utilization of Na-bentonite to Improve pH-buffering Capacity of Acid Sulfate Soils in Natural Gas Transmission Pipeline Rights-of-Way, Thailand

Abstract

Na-bentonite, non-hazardous material usually uses as a drilling mud in Horizontal Directional Drilling (HDD) technique. Its alkalinity may reduce severe acidic conditions of acid sulfate soils (ASS) in natural gas transmission pipeline Rights-of-Way in Thailand (RoW). This study focused on the effects of Na-bentonite on pH buffering capacity (pHBC) of ASS. Five major acid sulfate soils in RoW were collected and incubated with incremental amounts of 0.4 M Ca(OH)2 and 0.4 M HCl to determine their pHBC. Hydroxyl equivalent alkalinity derived from pHBC curves was used to define the appropriate rate of Na-bentonite. The various soil:Na-bentonite ratios of 1:0.1, 1:0.15, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:1 were prepared to examine their pH change. The results showed that active acid sulfate soils especially in subsoil had very high pHBC and Na-bentonite can increase soil pH to the optimal pH of 6.0, implying that Na-bentonite was beneficial for acid sulfate soils.