Industrial circulating water systems are crucial for many processes, but they are often plagued by the formation of inorganic scales, primarily calcium carbonate (CaCO3) and calcium sulfate (CaSO4). These scales can significantly reduce efficiency, increase operational costs, and lead to equipment damage. Traditional scale inhibitors, while effective, can sometimes pose environmental risks. This has driven the development of more sustainable and effective alternatives. Among these, polyaspartic acid (PASP) has emerged as a promising environmentally friendly option due to its biodegradability and low toxicity. However, its scale inhibition performance can be limited in certain demanding industrial applications.

Recognizing this, researchers have explored modifications to enhance PASP's capabilities. One significant advancement involves the modification of PASP with nanosilica, creating a composite material known as SiO2–NH2/PASP. This modification leverages the unique properties of nanosilica, such as its small size, large surface area, and high surface activity, to boost the scale inhibition performance of PASP. The synthesis typically involves a ring-opening reaction of polysuccinimide (PSI) in the presence of amino-functionalized nanosilica (SiO2–NH2), forming covalent bonds that integrate the nanosilica into the PASP polymer chain.

The resulting SiO2–NH2/PASP demonstrates markedly improved efficacy in preventing both CaCO3 and CaSO4 scaling compared to unmodified PASP. Studies have shown that at a mere 5 mg/L concentration, SiO2–NH2/PASP can provide a scale inhibition rate for CaCO3 that is up to 53% higher than that of pure PASP, and for CaSO4, it can be up to 21% higher. In some cases, the inhibition efficiency for CaSO4 can reach nearly 100% at concentrations as low as 6 mg/L. This enhanced performance is attributed to the increased number of carboxyl groups in the modified polymer, which allows for stronger chelation with calcium ions (Ca2+) and more effective adsorption onto the surfaces of nascent scale crystals.

The mechanism behind this improved performance is multifaceted. The carboxyl groups in SiO2–NH2/PASP act as chelating agents, binding with free Ca2+ ions in the solution and thereby preventing them from combining with sulfate or carbonate ions to form precipitates. Furthermore, the modified polymer adsorbs onto the surface of existing microcrystals, creating repulsive forces that prevent aggregation and deposition. Advanced analytical techniques such as Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and X-ray Photoelectron Spectroscopy (XPS) have been employed to confirm the structural integrity of the modified polymer and elucidate its interaction with scale crystals. SEM images reveal that SiO2–NH2/PASP alters the morphology of CaSO4 and CaCO3 crystals, leading to more irregular shapes and dispersed particles, rather than the dense, rod-shaped or blocky structures formed without inhibitors. XRD analysis shows that the modified PASP can influence the crystallization pathways, for instance, by promoting the formation of less stable vaterite in the case of CaCO3, thus disrupting the scale formation process. XPS studies further confirm the adsorption of the inhibitor onto the scale surfaces.

The advantages of using SiO2–NH2/PASP extend beyond its superior scale inhibition. It maintains good performance across a range of temperatures and test times, crucial for the dynamic conditions of industrial circulating water systems. Moreover, its environmental profile—being non-toxic and biodegradable—makes it a responsible choice for companies looking to minimize their ecological footprint. The integration of nanosilica not only enhances functional properties but also maintains the inherent environmental benefits of PASP, offering a powerful synergy. For businesses seeking reliable, eco-conscious solutions for their water treatment challenges, understanding the benefits of nanosilica modified polyaspartic acid is key to achieving efficient and sustainable operations.