CTAB-mediated lithium disilicate branched structures as superb adsorbents to remove Mn2+ in water

Removal of heavy metal Mn²⁺ ions in water is of great importance for human health and it is urgently needed to develop efficient adsorption materials. Here, a green and effective strategy to prepare mesoporous micro/nanostructured lithium disilicates (LDs) by employing the cation surfactant hexadecyltrimethyl-ammonium bromide (CTAB) as morphology control agent in hydrothermal environment, and investigated its adsorption behavior toward Mn²⁺ ions. The LDs possessed branched structures that were consisted of scattering pyramidal rods bestrewn with secondary nucleated and aggregated nanoparticles. Due to the mesoporous structures and negatively charged surfaces, LDs exhibited a high adsorption capacity up to 346.84 mg g⁻¹ with corresponding removal efficiency up to 99.82% when initial Mn²⁺ concentration was 82 mg L⁻¹, and their maximum adsorption capacity reached up to 785.25 mg g⁻¹ toward Mn²⁺ of 250 mg L⁻¹. Results indicated that the isotherm adsorption behavior of LDs was well described by mono-layer Langmuir model and kinetic adsorption fitted well with pseudo-second-order model, implying them the excellent chemical adsorbent to remove Mn²⁺ from wastewater. We believe this CTAB-modified approach could be extended to prepare other lithium silicates with mesoporous structures, rendering them wider applications in environmental protection.