Mg-Al LDH and Calcined LDH: Green Nanocatalysts for wet peroxide oxidation of phenol in wastewater

The catalytic wet peroxide oxidation (CWPO) of phenol from wastewater using Mg-Al LDH and calcined LDH at ۵۰۰ ºC was investigated. The LDH was synthesized by co-precipitation and characterized by XRD, FTIR, SEM, EDS and BET. XRD result showed that during calcination of LDH at ۵۰۰ ºC, LDH decomposed to the mixed oxide. The SEM images approved Mg-Al LDH comprised of flakes and the calcined LDH comprised of spherical nanoparticles. BET results indicated the specific surface area of ۱۰۰.۲ and ۸۶.۳ m۲.g-۱ for pure LDH and calcined LDH, respectively. The process was optimized by one factor at a time method and considering four process factors i.e. reaction temperature, peroxide dosage, initial phenol concentration, and reaction time. The optimum conditions resulted at initial phenol concentration of ۱۰۰ ppm, reaction temperature of ۶۰ ºC, with peroxide volume of ۳ mL and time on stream of ۴۵ min over calcined LDH with maximum ۸۵% removal of phenol. On the pure LDH, the maximum phenol removal (۷۹%) resulted at peroxide volume of ۲.۵ mL at ۵۵ min. The study concluded that the calcined Mg-Al LDH due to synergistic effect of MgO and Mg-Al mixed oxide showed higher catalytic activity despite a relatively low surface area.

Keywords:

Mg-Al LDH , Phenol , wet peroxide oxidation , Mixed metal oxide , Optimization