Research On Adsorption Behavior Of DNBP On Fly Ash And Modified Fly Ash

2-sec-butyl-4, 6-dinitrophenol(DNBP) is applied extensively as herbicide, pesticide and polymerization inhibitor for aromatic vinyl compound. A mass of highly toxic nitrophenol waste effluents are produced in the process of DNBP production. The waste water has caused not only many serious environmental problems, but also hindered further development of these production industries. At present, very little research on the treatment of DNBP wastewater can be found. In the paper, the adsorption behavior of DNBP in aqueous solution on fly ash and modified fly ash has been investigated by static adsorption technique. This research provides the potential application of fly ash as an adsorbent for the treatment of DNBP wastewater. The research in this paper involves two parts.In the first part of the paper, the effects of various factors, such as shaking time, frequence of shaking, initial concentration of DNBP, pH value, tempreture, particle size and inorganic anion on the adsorption capability of fly ash have been studied throughly. The adsorbility of fly ash was compared with that of activated carbon under the optimum adsorption condition. The results show that a lower pH value of solution and smaller particle size of fly ash is favourable for DNBP adsorption. Inorganic anions such as Cl^-, NO₃^-, SO₄^2- have a competition effect on the adsorption capability of fly ash. The adsorption capability of fly ash is superior to that of activated carbon when the initial concentration of DNBP is lower than 29mg/L, and the adsorption capability of fly ash can still achieve 98.2ï¼…-86.6ï¼…of the activated carbon when the initial concentration of DNBP is higher than 29mg/L. The adsorption capability of fly ash can be enhanced by modifing fly ash with hexadecyl trimethyl ammonium bromide(CTMAB). The adsorption capability of modified fly ash is superior to that of activated carbon in all concentrations of DNBP studied in this paper. The equilibrium amount of DNBP adsorbed increases from 6.45mg/g for fly ash to 8.78mg/g for modified fly ash. Compared with fly ash, the modified fly ash have a better adsorption capability in an extensively pH range.In the second part of the paper, the thermodynamics and kinetics in the process of adsorption of DNBP on fly ash and modified fly ash were analysed. The adsorption isotherms and kinetics models were applied to calculate the corresponding parameters. The results show that pseudo-second order kinetics model can describe the adsorption of DNBP on fly ash and modified fly ash very well. The process of adsorption of DNBP on fly ash and modified fly ash are controlled by film diffusion and particle diffusion. The adsorption isotherms of fly ash and modified fly ash can be fitted by both Langmuir and Freundlich models. The Freundlich parameters indicate the favorable case of the adsorption of DNBP on fly ash and modified fly ash, and the adsorption capability of modified fly ash for DNBP is larger than fly ash. The adsorption of DNBP on fly ash is an exothermic process accompaning the decrease of disorder of the system and can be occured spontaneously. The adsorption mechanism was proposed on the basis of analysis of morphology, surface area and Zeta potential of fly ash and modified fly ash. It can be concluded that hydrogen bond forces, dipole bond forces and Van der Waals forces maybe exist in the adsorption of DNBP on fly ash while hydrophobic bond force, Van der Waals forces and static function maybe exist in the adsorption of DNBP on modified fly ash.