Ethylenediamine-functionalized cubic ZIF-8 for arsenic adsorption from aqueous solution: Modeling, isotherms, kinetics and thermodynamics

Abstract

Metal-organic frameworks are novel adsorbents that have been widely used in recent years. The main properties of this emerging adsorbent include high specific surface area, significant porosity, regular structure and adjustable cavities. The main objective of this study was ZIF-8 synthesis with cubic structure, functionalization with ethylenediamine and evaluation for arsenic adsorption from aqueous environments. All the experiments were carried out in batch conditions. Main variables including pH, initial arsenic concentration, adsorbent dosage and contact time were evaluated in this work. In this study, Design of Experiment software was used for experimental runs order arrangement and better understanding of the variables effects on the process. The BET results showed that surface area of the synthesized ZIF-8 and ED-ZIF-8 was 910m2/g and 850m2/g, respectively. It was also revealed that before and after functionalization with ethylenediamine, ZIF-8 adsorbent was aminined at about 3mmol/g. In addition, the findings showed that the arsenic adsorption capacity increased from 72mg/g to 83.5mg/g. The best pH for arsenic adsorption was neutral (pH≈7). The co-existing of anions effect showed that bicarbonate, sulfate and chloride had the least inhibition effects on arsenic adsorption. This study showed that application of these class of adsorbents can be seriously addressed in solving some environmental challenges.