Studies on the use of metakaolin geopolymer for produced water treatment

Abstract

The looming crisis of drinking water scarcity and rapidly depleting fresh water resources in the world mandate that we minimize waste and maximize reuse of water. In the oil and gas (O&G) industry, produced water is a byproduct of O&G extraction, and is a major cause of wastewater generation. Current produced water handling practices include reinjection in disposal wells, evaporation in open, with minimal reuse. Recycling and re-use of produced water is the only solution to minimize the impact of the growing O&G operations on the future of fresh water supply and the environment. For this purpose, water treatment and technologies for handling the residual waste are required.

Membrane filtration, which relies on the pore size to separate contaminants is promising for produced water treatment. Commercial polymeric membranes are not suitable for produced water treatment due to their substantial maintenance and operation costs. Ceramic membranes on the other hand promise several advantages, including longer membrane life, high mechanical strength, superior chemical compatibility, and reduced process residuals. Unfortunately, the relatively high fabrication cost of ceramic membranes, which can range from hundreds to thousands of dollars per square meter of surface area, has restricted their wider application.

This study is the first-ever attempt to develop low-cost ceramic membranes with controlled porosity using geopolymers for produced water treatment. Membranes were processed as ceramic composites using geopolymers as the matrix phase and natural zeolites or biochar as the filler phase. A range of compositions, varying both the concentration and type of the filler phase, were processed under different conditions. The membranes were characterized for their microstructure and mechanical properties. The membrane performance was evaluated for flow rate and ability to remove particulate and dissolved impurities from produced water. This study confirmed that zeolite is an excellent choice as a filler phase to develop geopolymer composite membranes for treating produced water. In addition, the use of pure geopolymer phase to encapsulate residual waste was also evaluated. This study provides a framework for future studies on the development of novel geopolymer composites as membranes for water treatment and for residual waste encapsulation.