Hydrothermal tuning of morphology of aluminophosphate (AlPO-14) framework for the adsorption of Rhodamine 6G dye

Abstract

A crystalline zeolite material AlPO-14 was synthesized using Taiwanese coal fly ash (CFA) for the separation of cationic dyestuff Rhodamine 6G (R 6G) from aqueous stream. The zeolite synthesis was performed at different fusion ratios (CFA:NaOH) of 1:1, 1:1.5, and 1:2 followed by hydrothermal treatment resulted AlPO-14 zeolite frameworks (Z1, Z2, and Z3). The physico-chemical, structural, functional, morphological aspects of the raw CFA, and the zeolites were characterized via XRF, XRD, FT-IR, SEM, and BET methods. Further, the zeolites were tested their applicability adsorbing the cationic R 6G dye in batch mode. Moreover, the influence of pH, adsorbent dosage, initial dye concentration, temperature, agitation speed, kinetic models, adsorption isotherms on the removal of R 6G onto zeolites were emphasized. The results indicate that, neutral pH favors the separation of R 6G (qm = 208.11 mg/g) following Langmuir isotherm model, and best fitted to pseudo-second order kinetic model. Lastly, the adsorbent was responsive to the alkaline medium (NaOH), and can be readily retrieved for reuse, i.e., Z2 can be reused for 5 successive cycles, followed by Z1-3 times and Z3-2 times respectively. In summary, the major note downs were CFA based AlPO-14 had a commercial potentiality in adsorption applications and regarded to be a new entrant into zeolite database.