Nano-CaCO3-Based Materials from Steel Slag with Abundant Reaction Sites for Efficient Removal of Lead Ions and Methylene Blue

Dyes and lead ions (Pb²⁺) present a threat to human health. In this work, industrial solid waste steel slag was used as a raw material to extract and prepare Nano-CaCO₃. Afterward, a modified calcium carbonate adsorbent material (CaCO₃-KH550@TA) with a homogeneous morphology, and a stable structure was obtained by reacting with the silane coupling agent KH550 and tannic acid. It can effectively adsorb methylene blue (MB) and Pb²⁺. The adsorption experiments found that the maximum adsorption capacities for MB (pH 8, dosage = 0.06 g, time = 60 min, T = 323 K) and Pb²⁺ (pH 3, dosage = 0.06 g, time = 30 min, T = 323 K) were 122 and 130.6 mg/g, respectively. The pseudo-first-order kinetics and Langmuir model could describe the whole adsorption process well, indicating that CaCO₃-KH550@TA adsorption was chemical adsorption-dominated monolayer adsorption. SEM-EDS and XPS analyses revealed that the adsorption mechanisms were mainly hydrogen bonding, electrostatic attraction, and complexation. Therefore, CaCO₃-KH550@TA can be used as a potential adsorbent material for the treatment of polluted wastewater.