The efficient removal of diclofenac sodium and bromocresol green from aqueous solution by sea urchin-like Ni/Co-BTC bimetallic organic framework: adsorption isotherms, kinetics and mechanisms

Abstract

A novel adsorbent based on the nanostructured Ni/Co-BTC bimetallic organic framework (namely Ni/Co-BTC MOF) was successfully prepared by a simple solvothermal method. Adsorption experiments showed that the optimal molar ratio of Ni/Co in adsorbents was 1 : 2. Ni/Co-BTC MOF was characterized by various techniques, and the results showed that the nanoparticle was only 4 μm in diameter and 36.922 m² g⁻¹ in specific surface area. Kinetic and isothermal studies also showed that the adsorption process of Ni/Co-BTC-MOF to diclofenac sodium (DCF) and bromocresol green (BCG) can be well fitted with Langmuir and pseudo-second-order models. The maximum adsorption capacity of DCF and BCG reached 343.05 and 569.29 mg g⁻¹, respectively. The presence of free ions had no significant effect on the adsorption of DCF and BCG. Hydroxyl, π–π conjugates and metal oxygen groups played important roles in the adsorption of DCF and BCG, and Ni/Co-BTC-MOF was also involved in electrostatic action when adsorbing DCF. In addition, when used after regeneration, the prepared adsorbent had a stable adsorption capacity. The Ni/CO BTC MOF material with high adsorption performance prepared in this study shares some new insights in the removal of organic pollutants.