Polyaspartic acid-modified sulfur quantum dots as a triple-function antiscalant, antibacterial agent, and fluorescence tracer for industrial water treatment

In high-temperature industrial water systems, developing environmentally friendly and efficient water treatment agents is crucial for inhibiting mineral scale formation and microbial contamination. In this study, a novel multifunctional water treatment agent, PASP-SQDs, was synthesized by modifying sulfur quantum dots (SQDs) with polyaspartic acid (PASP), endowing it with high-efficiency scale inhibition, antibacterial properties, and fluorescent tracing capabilities. The microstructure and spectral characteristics of PASP-SQDs were analyzed using X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, ultraviolet-visible spectroscopy, and fluorescence spectrophotometry. Notably, PASP-SQDs exhibited excellent fluorescence properties, enabling their use as a tracer for accurate dosing and real-time concentration monitoring of water treatment agents. This feature significantly enhances their practical applicability, allowing for intelligent and efficient water quality management. Static scale inhibition experiments were conducted to evaluate the inhibitory effects of PASP-SQDs on calcium carbonate (CaCO₃) and calcium sulfate (CaSO₄) scale formation, along with assessing their antibacterial performance. The results showed that PASP-SQDs significantly outperformed PASP alone, achieving scale inhibition rates of nearly 90 % for CaCO₃ (at 25 mg/L) and 98 % for CaSO₄ (at 0.6 mg/L). Additionally, at a concentration of 180 mg/L, PASP-SQDs exhibited an antibacterial efficiency exceeding 99 %, effectively preventing microbial contamination in water systems. The scale inhibition mechanism of PASP-SQDs was further investigated using X-ray diffraction, scanning electron microscopy, molecular dynamics simulations, and quantum chemical calculations. This study provides a comprehensive understanding of the working mechanism of PASP-SQDs, laying a solid theoretical and practical foundation for the development of next-generation, multifunctional, eco-friendly, and highly efficient water treatment agents.