pH-Responsive Water-Based Drilling Fluids Containing Bentonite and Chitin Nanocrystals

The forthcoming era of sustainable development demands the utilization of naturally abundant, sustainable, biodegradable, and environmentally friendly resources for a wide variety of applications. Herein, we report the isolation of chitin nanocrystals (ChNCs) from speckled swimming crab shell waste and their novel utilization as rheology modifiers in bentonite-water-based drilling fluids (BT-WDFs). The positively charged functional groups on the surface of ChNCs enable them to attach to the negatively charged face surfaces of BT by electrostatic attraction, leading to a notable improvement in the rheological property that is responsible for the ability of drilling fluids to carry away drill cuttings. Moreover, owing to the reversible protonation and deprotonation of ChNCs and BT platelets, ChNC/BT-WDFs can form distinctive dispersion states and nanostructured surface interactions under different pH conditions. As a result, ChNC/BT-WDFs exhibit interesting pH responsive theological and filtration performance, especially when the pH is changed from neutral to acidic. Finally, the combined use of ChNCs with a conventional filtration control agent polyanionic cellulose (PAC) leads to remarkable improvement in both rheological and filtration performance of BT-WDFs. It is expected that these observations not only enrich the high-value utilization of crab shell waste but also advance the development of smart nanofluids with pH-responsiveness for various applications.