Preparation Of Modified Asphalt Adsorbent And Its Application In Dye Wastewater Treatment

Chemical synthetic dyes are widely used in the printing and dyeing industry due to the increasing demand for printing and dyeing products,resulting in a sharp rise in the amount of dye wastewater.Methylene blue(MB),Congo red(CR)and other azo dyes and their metabolites contain benzene rings,which are not only harmful to human health,but also destroy the photosynthesis of aquatic ecology.Therefore,there is an urgent need to develop fast,simple and low-cost wastewater treatment technologies and related new materials.In this paper,based on the treatment strategy of dye wastewater by adsorption method,a kind of efficient carbon based adsorbent CTPA was prepared using the industrial solid waste coal tar pitch(CTP)as carbon source through the combination of strong alkali activation method and non-oxidation calcination method.In addition,another adsorbent CM was prepared by selecting another kind of industrial solid waste oil shale semi-coke(SC)as raw material and calcined with CTP togather.X-ray diffraction(XRD),Scanning Electron Microscopy(SEM)and Fourier Transform Infrared Spectroscopy(FT-IR)were intoduced to characterize the samples.The adsorption properties and adsorption mechanisms of the adsorbates were studied in detail using the dyes MB and CR as target pollutants.The main research contents are as follows:(1)A new adsorbent CTPA was prepared by activating CTP with KOH at high temperatures.CTPA has a steep surface roughness and a section abundant in micropores,and has excellent adsorption properties for MB(1724.17 mg/g at 303 K,1867.09 mg/g at 313 K,and 2049.95mg/g at 323 K).Zeta potential analysis shows that electrostatic adsorption plays an essential role in the adsorption process.Statistical physics models of bilayer adsorption strongly describe the aggregation behavior of MB on CTPA.Studies of the Site energy analysis(SED theory)have shown that increasing the temperature increases the trapping capacity of the molecule and the number of adsorption sites of the adsorbate,thus promoting an increase in the adsorption capacity.Desorption and re-adsorption experiments have shown that CTPA is an excellent adsorbing material with excellent stability of the adsorption cycle.(2)Asphalt/semi-coke composite CM was prepared by elevated temperature calcination(KOH as activator)using CTP as carbon source and MSC as precursor.The adsorption capacity of the CM is 848.56 mg/g for MB and 430.57 mg/g for CR.SEM image analysis revealed that the large lamellar structure in the SC was corroded by KOH and peeled into minor fragments,which then showed chaotic cross-link aggregation under penetration and encapsulation of asphalt solution,forming a rough surface.The XRD pattern shows that the crystalline phases of SC and intermediate MSC disappear on the CM surface.At the same time,fresh silica and sic nanoparticles are generated on the surface of CM.(3)The adsorption properties and mechanisms of MB were investigated by treating MB dye wastewater with bitumen/semi-coke composite CM as an adsorbent.CM has excellent adsorption properties for MB(918.21 mg/g at 303 K,936.50 mg/g at 313 K and 966.72 mg/g at 323 K).The kinetic fitting results show that the quasi-second-order kinetic model can describe the adsorption process of CM adsorbing MB more accurately.The adsorption process is more of an intra-particle diffusion process and the adsorption rate is controlled by chemisorption.The Zeta potential and Langmuir model analysis show that chemisorption and electrostatic interactions are the dominant binding modes in the adsorption process.Analysis of the SED theory shows that the number of high-energy sites increases as the contact temperature increases,thus promoting the adsorption of MB.Desorption and re-adsorption experiments show that the CM is remarkably stable over the adsorption cycle,which is promising for practical applications.(4)Asphalt/semi-coke composite CM was used as an adsorbent to treat CR dye wastewater and its adsorption properties and CR mechanism were investigated.At T=303 K,the adsorption capacity of CM on CR is 457.13 mg/g.In-particle diffusion models and quasi-second order kinetic models can accurately describe the adsorption process of CM on CR,where the adsorption process is dominated by in-particle diffusion and the adsorption rate is controlled by chemisorption.The Zeta potential analysis shows that electrostatic adsorption also plays an essential role.The Hill physical model speculates that multiple CR molecules interact with multiple adsorption sites.SED theory based on this model showed that with the increase of contact temperature,the number of high-energy sites would increase,thus promoting the adsorption of MB.The desorption and re-adsorption experiments showed that CM still had a excellent adsorption performance for CR when five cycles of adsorption were completed.