The formation of sparingly soluble and insoluble inorganic salts (i.e., scale deposits) is a major problem for industrial and domestic water transportation. To control scale deposits, chemical scale inhibitors are commonly used. Commercial antiscaling agents include polyelectrolytes that dissociate phosphonates, carboxylates, and sulfonates anionic groups. However, it is imperative to identify highly efficient polymeric inhibitors and environmentally friendly antiscalants, in particular, to replace phosphonate inhibitors due to their environmental risks. Certain polypeptides with charged groups have been extracted from organisms and found to efficiently control the nucleation and crystallization of minerals. Their structures are attractive models for better understanding the inhibitor-mineral interactions and designing next generation antiscalants. Ice-binding proteins or antifreeze proteins (AFPs) from cold-adapted organisms (e.g., fish, insects, and plants) can bind to specific ice surfaces, thereby inhibiting the nucleation and crystallization of ice. AFPs cam also control the crystallization of some non-ice like compounds by interacting with the crystalline surfaces of these compounds. We correlate the charge and molecular properties of the polyelectrolytes with their efficiencies in inhibiting the scale crystal formation. A beetle AFP from Tenebrio molitor (TmAFP) having regular spaced charged residues on its surfaces is prepared and studied here. Calcium carbonate (CaCO3), a common scale deposit, is a scalent of interest in this study. We investigate the effects of TmAFP on the formation of CaCO3. Our results show that the presence of TmAFP inhibits the formation of CaCO3 resulting much fewer and smaller CaCO3 crystals. The achieved CaCO3 crystals in the absence and presence of TmAFP are both characterized to be calcite using Fourier transform infrared (FTIR) spectroscopy and mass spectrometry (MS), which suggests that the presence of TmAFP does not change the polymorph of CaCO3. By analyzing the charged residues on the surfaces of TmAFP and calcite surfaces, we propose that TmAFP may affect the formation of calcite via adsorption to the crystalline surfaces of CaCO3. This study provides better understanding for scale control as well as new designs for green antiscalants.

Effects of ice-binding proteins from cold-adapted insect Tenebrio molitor on calcite crystallization

253rd National Meeting (2017)

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