A microwave-activated coal fly ash catalyst for the oxidative elimination of organic pollutants in a Fenton-like process

Surfactant modified waste ash for the removal of chloro and nitro group substituted benzene from wastewater

A surfactant-modified coal fly ash was developed as a multifunctional adsorbent for the removal of organic pollutants from wastewater. Sodium dodecyl sulfate (SDS) was used to modify the surface of coal fly ash (CFA). The modified CFA was characterized using scanning electron microscopy (SEM), surface porosity analyzer, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The results showed that loading CFA with SDS not only improved the functionality and surface morphology of the raw ash for the adsorption of organic pollutants, but also enhanced its thermal stability. The efficiency of the modified fly ash was tested in terms of removal of two non-polar organic pollutants namely chlorobenzene (CB) and nitrobenzene (NB) from aqueous phase. The maximum uptake capacity of chlorobenzene and nitrobenzene with SDS-modified coal fly ash (SCFA) was 225 mg/g and 90 mg/g, respectively. The kinetic analysis was done by controlled kinetic models, i.e., pseudo first and second order kinetic models. The results showed that adsorption of CB and NB onto SCFA followed a pseudo second order kinetic model. The adsorption of chlorobenzene was exothermic over the modified adsorbent while nitrobenzene showed an endothermic behavior. The isotherm analysis depicted the multilayer adsorption of both pollutants onto the surface of the surfactant modified adsorbent. This work has shown that surface modification using surfactants can be a viable option to enhance the adsorption capacity of fly ash for pollutants removal.

Formation of Fly Ash Catalysts and Selection of a Matrix Binder and Its Application in Denitration

The development of high-efficiency and low-cost new catalysts is an extremely attractive topic. In this study, two different matrix bentonite-modified fly ash catalysts were successfully prepared, and the compressive strength of the catalyst was studied by using unsaturated dynamic and static triaxial technology. The axial compressive strength of FC (fly ash catalysts added with Ca-based bentonite) was greater than that of FN (fly ash catalysts added with Na-based bentonite). The catalyst reached 978 kPa. The prepared catalyst was characterized by X-ray diffraction analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, and specific surface area analysis (BET) of the catalyst. In addition, denitration performance of different catalysts was explored, and the reaction conditions were optimized. The results demonstrate that when the mixing ratio of fly ash and calcium-based bentonite in the FC is 4:1, the compressive strength is relatively high, and the denitration rate reaches about 82%.

Studies on the Potential of Nonmodified and Metal Oxide-Modified Coal Fly Ash Zeolites For Adsorption of Heavy Metals and Catalytic Degradation of Organics for Waste Water Recovery

A nanocrystalline zeolite of Na-X type (CFAZ) was synthesized by ultrasonic-assisted double stage fusion-hydrothermal alkaline conversion of lignite coal fly ash. Modified CFAZ with magnetic nanoparticles (MNP-CFAZ) was obtained by adding presynthesized magnetic nanoparticles between the synthesis stages. CFAZs loaded by particles of copper (Cu-CFAZ) and cobalt (Co-CFAZ) oxides were prepared by postsynthesis modification of the parent CFAZ, applying a wet impregnation technique. The parent and modified CFAZs were examined for their phase composition by X-ray diffraction, morphology by scanning electron microscopy, and surface characteristics by N2 physisorption. Comparative studies have been carried out on the adsorption capacity of the starting CFAZ and its derivatives with respect to Cd2+- and Pb2+-ions from aqueous solutions. Adsorption isotherms of Cd2+-ions on the studied samples were plotted and described by the adsorption equations of Langmuir, Freundlich, Langmuir–Freundlich, and Temkin. The best correlation between the experimental and model isotherms for the parent and modified CFAZ was found with the Langmuir linear model, assuming a monolayer adsorption mechanism. Parent and modified CFAZs were also studied as catalysts for heterogeneous thermal Fenton oxidation of methylene blue. At 90 °C, the higher catalytic activity exhibits the nonmodified sample, but with the decrease in temperature to 60 °C, the modified samples are more effective catalysts.