Adsorption characteristics of Na-A zeolites synthesized from Egyptian kaolinite for manganese in aqueous solutions: Response surface modeling and optimization

Egyptian kaolinite was processed to synthesize NaA zeolites; zeolite by calcination (ZC) and zeolite by alkali fusion (ZF). Characterization of the prepared zeolites was carried out using X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) surface area. The influence of initial manganese (Mn^2 +) concentration, contact time and zeolite dose in manganese uptake by ZC and ZF were studied. The removal efficiency of ZF for ions was high compared to that of ZC at all contact times and adsorbent masses. The adsorption characteristics for Mn^2 + were described well using the Langmuir and the pseudo-second order equations. Optimization of Mn^2 + uptake using the experimental runs of the response surface methodology (RSM) indicated that the maximum manganese removal efficiency by ZC and ZF was 82.2% and 99.96%, respectively, at the conditions of 50 mg/L of manganese concentration, 500 min of contact time and 1.4 g of dose. According to the polynomial model, the dose of ZF (0.9 to 1.12 g) at contact time (190 to 340 min) was predicted to enhance the maximum removal efficiency of manganese (50 mg/L) to 100%. In ZC case, the maximum removal efficiency of Mn^2 + was not improved using the RSM design.