Effective Congo red dye adsorption using mesoporous zinc-based metal organic framework in aqueous media: kinetics and mechanism studies

Adsorption is one of the most environmentally beneficial ways to successfully remove toxins from the aquatic environment. One of the main sources of COD contaminants in industrial wastewaters is Congo red (CR), a popular azo dye chemical utilized in many industrial processes. Because of excessive CR discharges have had a negative influence on aquatic ecosystems and biological systems. Thus, removing CR from aqueous habitats is critical for wastewater treatment. For that, we prepared a zinc-based metal organic framework (MOF-5) by a straightforward solvothermal procedure and characterized it using various analytical techniques. The effects of pH, adsorbent quantity, and concentration on the dye solution were examined using CR as the adsorbate. Under ideal conditions (pH 9, adsorbent quantity of 20 mg, and dye concentration of 15 ppm), simulated second-order kinetics and Langmuir isotherms are utilized to more precisely explain the MOF-5 adsorption process and are supported by the error analysis model. During the adsorption experiment, the maximum adsorption capacity measured was 351.86 mg/g. Furthermore, after adsorption, the CR dye was released using an organic solvent. MOF-5 demonstrated consistent and excellent adsorption performance across five cycles. MOF-5 selectively adsorbs CR to a weak hydrogen bond and π–π stacking interaction with the adsorbate.HIGHLIGHTS Metal-organic framework-5 is synthesized using the solvothermal method.Synthesized material was characterized by various techniques.15 ppm Congo red dye solution for 20 mg of adsorbent at pH 9, 99.73% of adsorption was observed in 10 min.Adsorption studies use the Langmuir isotherm and pseudo-second-order kinetics, indicating a linear monolayer adsorption based on the separation factor.MOF-5 demonstrated the highest adsorption capacity of 351.86 mg/g.