A Study On The Adsorption Of Typical Organic Pollutants By Pine Sawdust Pyrolysis Char Modified By H₃PO₄-Microwave

In this research, H3PO4-microwave method was used to modify the pine sawdust pyrolytic char(PyC). The best condition of modification was discussed.The percent of H3PO4concentration was50%, soaking ratio (solid-liquid ratio) for1:5, microwave power for380W, microwave time for2min. After modification, the adsorption performance of pyrolytic char was greatly improved. The characterization of PyC and modified PyC (APC) was analyzed by element analysis, BET, FTIR, XRF, SEM, XRD and Boehm titration. The results Indicated that the pore structure of APC was more loose, the surface area was increased, the surface structure of APC was changed greatly.The research used APC as adsorbent, for removal parachlorophenol (ρ-CP),4-chlorine-2,5-dimethoxy nitrobenzene(CDNP) and paranitrophenol(ρ-NP) in a single system. The reuse of APC and competitive adsorption between ρ-CP and ρ-NP on APC were studied. The influence factors of adsorption conditions, such as adsorbent dosage, pH, contact time, salt concentration, initial concentration and temperature were investigated. The experimental results were as follows:(1) In the adsorption of ρ-CP on APC, best solution pH was2<pH<7, the salt concentration had no effect on adsorption behavior. The Freundlich and Koble-Corrigan model better fitted the adsorption isotherm of APC-ρ-CP system. Pseudo-second-order kinetic model describled well the adsorption dynamics process of APC-ρ-CP system in low concentration, Double-constant model and Elovich model better fitted in high concentration. Elovich equations better describled the desorption process.Thermodynamic parameters showed that the adsorption process was entropy reduction, spontaneous, exothermic and physical adsorption.(2) In the adsorption of CDNP on APC, best solution pH was2<pH<5, the salt concentration had no effect on adsorption behavior. The Temkin model better fitted the adsorption isotherm of CDNP-APC system. Pseudo-second-order kinetic model and Elovich model describled well the adsorption dynamics process of CDNP on APC. Thermodynamic parameters showed that the adsorption process was spontaneous and physical adsorption.(3) In the adsorption of ρ-NP on APC, best solution pH was6<pH<11, the adsorption capacity increased and then decreased with the increase of salt concentration. The Koble-Corrigan model better fitted the adsorption isotherm. Elovich model describled well the adsorption dynamics process. Thermodynamic parameters showed that the adsorption process was entropy reduction, spontaneous, exothermic and physical adsorption.(4) In competitive adsorption between ρ-CP and ρ-NP, APC adsorbed p-NP preferentially, after the adsorption equilibrium of ρ-NP on APC, the adsorption of ρ-CP on APC became equilibrium.The adsorption quantity of a component in mixture is less than that in single component system. The adsorption of ρ-CP on APC is affected greater by competitive adsorption.