Factorial experimental design for the optimization of highly selective adsorption removal of lead and copper ions using metal organic framework MOF-2 (Cd)

This paper reports the ultrasonic synthesis of a cadmium terephthalate metal-organic framework MOF-2 (Cd), CdTPA at room temperature as adsorbent for high efficiency ultrasonic assisted removal of lead and copper from aqueous solution. The MOF-2 (Cd) was characterized using XRD, EDS, FT-IR and SEM techniques. In order to assess the impact of various variables affecting the adsorption of lead (Pb) and copper (Cu), a factorial design analysis was used. The parameters examined contain; sonication time, initial concentration and adsorbent dose. It was seen that the adsorbent dosage effect was most significant and exhibited a positive effect for the removal efficiency of both lead and copper. The removal percentage values of 99.9 and 97.9% were achieved using 1.0 g adsorbent dose for lead and copper, respectively. It was established that the kinetic of adsorption followed pseudo-second order model with coefficient of determination values of 0.9998 and 0.9999 respectively for Pb2+ and Cu2+ ions. The isotherm of adsorption of both lead and copper followed Langmuir isotherm with maximum monolayer adsorption capacity of 434.78 and 76923 mg/g respectively for copper and lead. The MOF-2 (Cd) reveals chemical stability against common organic solvents for instance DMF, CAN, methanol and aqueous solution with different pHs except at pH 2. The thermal stability of MOF-2 (Cd) was demonstrated by TGA. The high temperature structure of the MOF-2 (Cd) (400 degrees C) exhibits the thermal stability of the MOF-2 (Cd). Furthermore, the reuse results illustrate that the MOF-2 (Cd) can be used for at least three times for the removal of Pb and Cu ions from aqueous solutions due to its durability and stability. (C) 2018 Elsevier B.V. All rights reserved.