Study On Removal Of Typical Pollutants From Aqueous Solution By Modified Diatomitete

The water pollution was becoming more and more serious,and has threatened the health of human and the stability of ecosystems,especially the problems caused by organic pollutants.So looking for an effective treatment method of organic pollutants is particularly urgent.Various techniques have been used to remove the organic pollutants,however,adsorption was considered to be one of the best feasibility technologies,and diatomite have attracted much attention by considering its cheapness,stable properties,great capabilities in adsorption,and it's convenience of regeneration.This paper emphasizes the removal kinetics and mechanism of tipical organic pollutants?aniline and phenol?in water by manganese modified diatomite.Aming at the diatomite used in the study,novel rapid green one-step method was developed for the preparation of manganese modified diatomite?Mn-D?by treating roasted diatomite with an acidic permanganate solution.In this paper,Mn-D was characterized by Brunauer–Emmett–Teller analysis?BET?,X-ray diffractometry?XRD?,Scanning electron microscopy?SEM?,Fourier transform infrared spectroscopy?FTIR?and X-ray photoelectron spectroscopy?XPS?and measured some performance parameters.The adsorption and oxidation of Mn-D was studied,the optimum preparation process was determined,the effects of time,dosage,ionic strength,pH,temperature and the interaction between manganese oxide and diatomite were investigated.The removal kinetics,mechanism and reaction intermediates of aniline by Mn-D were also discussed.The major results are as follows:The surface area of Mn-D was 48.94 m² g^-1,the zero charge points(pH_ZPC)was 2.62,and the loading amounts of manganese oxide was 0.82g g^-1.The SEM showed that the manganese oxide were loaded on the Mn-D evenly and wasn't plugged the channel when the mass ratio of KMnO₄ and diatomite???was 1.6.XRD and XPS pattern of Mn-D showed that the manganese oxide was?-MnO₂,including MnO₂,MnO and their hydrates,Mn⁴⁺was the main valence state.FTIR spectra found the characteristic adsorption peaks of?-MnO₂ and the exists of surface hydroxyl,silicon hydroxyl and siloxane.The properties and optimal condition for Mn-D to remove aniline were investigated.The results showed that when the optimal calcination temperature was 450?,?was 1.6.The adsorbent velocity was quick,and more than 80%of aniline was adsorbed in 10 minutes,accompanied with the release of Mn²⁺.Acidity condition,higher temperature and dosage were favorable,and the effect of ionic strength was first increased and then decreased,manganese and diatomite showed synergistic effects.The removal rate was 85.89%when the pH was 5.0,temperature 25?,?was1.6,dosage was 2.0 g L^-1 and the initial concention of aniline was 100 mg L^-1,the saturated adsorption amounts was 41.75 mg g^-1,and the equilibrium time was 1 h.In acidic conditions,the adsorption process on Mn-D followed pseudo-second-order and was mainly controlled by intra-particle diffusion.The best fit for the experimental adsorption data was given by the Freundlich.The FTIR and XPS showed that Mn-D adsorbed aniline by silanol groups and manganese hydroxyl,while the manganese showed adsorption and oxidation ability.GC-MS was applied to identity the reaction intermediates at different times,and azobenzene was found to be the main reaction intermediate in the degradation system.The removal of pheonl by Mn-D was similar with aniine,but had slightly different.The optimal synthesized conditions were the same,namely,calcination temperature was 450?and?was 1.6.While the adsorbent velocity was slower than aniline,and only 60%of phenol was adsorbed in 30 minutes.The removal rate was 86.5%when the pH was6.0,temperature 25?,?was 1.6,dosage was 2.0 g L^-1 and the initial concention of phenol was 100 mg L^-1,the saturated adsorption amounts was 43.27 mg g^-1.In acidic conditions,the adsorption process on Mn-D followed pseudo-second-order and was mainly controlled by the proliferating in the fluid film and inside the grains.The best fit for the experimental adsorption data was also given by the Freundlich.The FTIR and XPS showed manganese showed adsorption and oxidation ability,and the oxidation was more obvious.GC-MS showed that benzoquinone was the main reaction intermediate in the degradation system.We also investigated the removal of compound pollutants,the results showed that,the removal rate of aniline and phenol were significantly reduced with the increasing of initial concentration,when the concentration of aniline and phenol were single.But the removal rate of phenol decline was faster than aniline.The effect of different concentrations of aniline and phenol were also investigated.Research showed that the main adsorption mechanism of anilin and phenol were surface adsorption and partitioning effect.They share some adsorption sites,but also have different,and the adsorption periods were different.