A sustainable strategy for complex wastewater treatment: Sequential capture and facile regeneration of Cu(II) and tetracycline using C-A-S-H

As water pollution has grown progressively serious in recent years, the development of the adsorbents possessing both high-efficiency and reusable characteristics has emerged as a key area of focus demanding urgent attention. This work aims to realize the high adsorption efficiency and sustainable use of C-A-S-H to adapt to increasingly complex application scenarios. A hydrothermal route was adopted for the synthesis of the aluminum-doped hydrated calcium silicate (C-A-S-H). Cu(II) and tetracycline (TC) were adsorbed sequentially through a continuous process to investigate the adsorption behavior and mechanisms, followed by the realization of a facile regeneration method. The maximum adsorption capacity of C-A-S-H for Cu(II) at 25 °C reached 528.05 mg·g −1 . Subsequently, C-A-S-H(Cu) exhibited an adsorption capacity of 300.34 mg·g −1 for TC. The reusability of the adsorbent was confirmed, as it sustained over 98% of its initial adsorption capacity throughout five successive cycles of use and regeneration. The lower mass loss of C-A-S-H during adsorption cycles is attributed to its better stability relative to C-S-H. Additionally, it provides a possibility for the recovery of calcium ions. This work emphasizes the high adsorption efficiency and sustainability of C-A-S-H, revealing that surface precipitation is the dominant mechanism for Cu(II) uptake, whereas the interaction with TC is governed by coordination complexation. Its effectiveness in treating the complex effluents containing both the heavy metal ions and antibiotics underscores its value as a sustainable and environmentally friendly solution.