Abstract
p-Nitroaniline (PNAN) and nitrobenzene (NB) being important raw materials and intermediates for the production of a wide range of chemical products have the potential of constituting water pollutants. Hence, the development of the means of removing these chemicals from water would go a long way to safeguard the health of the environment. The goal of this research was to transform bagasse fly ash (BFA), solid waste from the sugar industry into porous zeolitic adsorbents MgFZBFA and MgMZBFA and examine them for their adsorptive removal of PNAN and NB from aqueous solutions. The syntheses of the sorbents involve alkali fusion technique and microwave hydrothermal treatment for the desired properties. Advanced characterization techniques such as FTIR (Fourier transform infrared spectroscopy), XRF (X-ray fluorescence spectroscopy), XRD (X-ray diffraction spectroscopy), SEM (scanning electron microscopy), Brunauer–Emmett–Teller (BET)/Barrett–Joyner–Halenda (BJH) Method, and TGA (thermogravimetric analysis) were used for the characterization and evaluation of the sorbents’ properties. The adsorptive removal of PNAN and NB from aqueous solutions by MgFZBFA and MgMZBFA were investigated. Various parameters such as pH, adsorbent dosage, initial sorbate concentration were optimized during the adsorption experiment to achieve best performance. Adsorption isotherm, kinetics and dynamics were studied. It was found that Langmuir adsorption isotherm model better represents the adsorption processes and that the processes follow pseudo-second-order kinetics. More so, the sorption processes were most possibly completed by both surface sorption (liquid-film diffusion) and intra-particle diffusion. The maximum sorption capacities observed with MgFZBFA for PNAN and NB are 30.86 mg g−1 and 19.92 mg g−1, while with MgMZBFA the values are 12.72 mg g−1 and 10.20 mg g−1, respectively. The performances of MgFZBFA and MgMZBFA for the sorption of PNAN and NB were compared with some adsorbents previously studied for the same purpose, and results show that the adsorbents in the present study exhibit better performances. The application as materials of cheap source for the removal of PNAN and NB from contaminated water could be considered.
Highlights
Studies on natural zeolites being used as adsorbents for wastewater treatment have attracted great attention due to their porous nature which gives them the potential to entrap water pollutants (Wang and Peng 2010)
Results obtained from the Barrett– Joyner–Halenda (BJH)/BET analysis of the adsorbent samples show that the surface area and the pore volume of MgFZBFA are greater than those of MgMZBFA (Table 3)
The results obtained for the bulk densities of MgFZBFA and MgMZBFA are in accordance with the inverse trend of the cumulative pore volumes associated with the adsorbents, i.e., on comparing the two adsorbents, the decrease in the magnitude of density was observed with increase in the cumulative pores of the adsorbents
Summary
Studies on natural zeolites being used as adsorbents for wastewater treatment have attracted great attention due to their porous nature which gives them the potential to entrap water pollutants (Wang and Peng 2010). The presence of triply charged aluminium in the tetrahedra arrangements results in the generation of a net negative charge in the framework which creates an avenue for the framework to be balanced by metal ions. Such metal ions could generate strong local electric fields and attract the negative centers of polar molecules to the surface of a zeolite (Xu et al 2007). Bagasse fly ash is a solid waste generated from the sugar industry and available in ample of amount with negligible cost It contains high amount of silica which is the primary building block of zeolitic materials. The outcome of this research could suggest additional ways to put fly ash into use, and more importantly, serving as a cheap raw material for mitigating water pollution
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