Study On Preparation Of Nitrogenous Biochar Materials And Treatment Of Phenol Wastewater

Advanced oxidation processes（AOPs）with persulfate as oxidant has attracted much attention because of its comprehensive application,fast reaction rate and strong oxidation ability.Biochar has a large surface area and abundant surface functional groups,which can effectively activate persulfate,which can decompose into oxides to treat phenol-containing wastewater.In this study,self-doped nitrogen-containing biochar was prepared using two nitrogen-containing materials,chitosan and shrimp shell,as precursors and used to activate persulfate for the treatment of phenol-containing wastewater.（1）The nitrogen-containing biochar was prepared by one-step pyrolysis of high-temperature calcination of chitosan,which realized the self-doping of nitrogen in carbon materials.The surface structure,surface functional groups and elemental composition of BC-N were analyzed by scanning electron microscopy,energy dispersive spectroscopy,X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.The chitosan biochar（BC-N）,prepared when the charring temperature was 500℃and the mass ratio of chitosan and zinc chloride（ZnCl₂）was 1:2,was the most effective for phenol removal by activating persulfate（PDS）.The reaction conditions of SBC activated persulfate system（SBC/PDS）for treating phenol-containing wastewater were explored and optimized.When the dosage of BC-N was0.20 g/L,the dosage of persulfate was 0.6 g/L,and no adjustment of initial pH,the removal rate of phenol of 0.10 g/L could reach 98%and the corresponding mineralization efficiency could reach 80%in 120 min.The system has good removal effect on acidic and neutral phenol wastewater and high salinity wastewater.The oxidation species that played a major role in the oxidative degradation of phenol was singlet oxygen generated by the decomposition of BC-N activated persulfate.（2）When charring temperature was 800℃and the mass ratio of shrimp shell and zinc chloride was 1:1,the shrimp shell biochar（SBC）prepared by one-step pyrolysis had the best effect on phenol removal by activating persulfate.SBC was characterized by scanning electron microscopy,energy dispersive spectroscopy,X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.The reaction parameters of SBC activated persulfate system（SBC/PDS）for treating phenol-containing wastewater were optimized.When the concentration of phenol was 0.10 g/L,the dosage of SBC was0.20 g/L and the dosage of persulfate was 0.6 g/L,98%phenol removal rate and 80%phenol mineralization rate were achieved after reaction for 120 min in the initial pH.The non-radical singlet oxygen played a major role in the degradation process of phenol,while free radical played a minor role.Compared with BC-N/PDS system,SBC/PDS system can be applied to a wider range of pH,and can activate persulfate to treat phenolic wastewater at pH=1-9,and has a higher tolerance to salt ions and common ions.（3）The shrimp shell biochar was modified by loading with manganese chloride（MnCl₂）.When charring temperature was 800℃and the mass ratio of shrimp shell and manganese chloride was 3:1,the shrimp shell biochar loaded by manganese（SBC-Mn）had the best effect on phenol removal by activating persulfate.SBC-Mn was characterized by scanning electron microscopy,energy dispersive spectroscopy,X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy.The experimental conditions of SBC activated persulfate system（SBC-Mn/PDS）for the treatment of phenol wastewater were optimized.Under the conditions:phenol concentration was 0.10 g/L,SBC-Mn dosage was 0.20 g/L,persulfate dosage was 0.6g/L,and no adjustment of initial pH,the removal rate of phenol was 98%,and the corresponding phenol mineralization rate was 81%.In this system,more than 95%phenol removal can be reached in 60 min,and it has ideal treatment effect for phenol wastewater with pH=1-9.The removal rate of phenol can also reach more than 90%under the interference of high concentration of common ions.