Study On The Preparation Of Biochar Functional Materials For The Removal Of Organic Pollutants

Phenolic pollutants have the characteristics of wide distribution,substantial toxicity and poor biodegradability,which have caused severe harm to human health and the ecosystem.Therefore,it is of considerable significance to research and develop an efficient and environment-friendly wastewater treatment method for environmental protection.Biochar has attracted extensive attention due to its wide range of raw materials sources,low cost,environment-friendly and excellent stability.However,traditional biochar materials have a small specific surface area and poor adsorption performance,which limit their applications in wastewater treatment.A large number of studies use modified methods to improve the removal performance of biochar for pollutants,but there are few reports on the removal of phenolic pollutants.Photocatalysis has attracted much attention because of its ability to convert harmful substances into harmless through light illumination.Titanium dioxide（Ti）is the most common photocatalyst,which has the characteristics of high photocatalytic activity,strong chemical stability and non-toxicity.However,it has been restricted in practical applications due to the limitations of adsorption capacity,light utilization rate,preparation process and recycling.In this study,a variety of modified biochar and its functional material compounded with laboratory-synthesized titanium dioxide were prepared using phoenix leaves as raw materials and applied to the removal of phenolic pollutants.The research results are as follows:（1）Biochar with microporous and hierarchically porous structure was prepared via stage calcination by using KOH as the activator,with a specific surface area and pore volume of 1,792.38 m²/g and 0.94 m³/g,respectively.A large number of hydroxyls,carboxyl,benzene ring and other functional groups were found on the surface of biochar.Under the acidic condition,these functional groups can remove p-nitrophenol by the hydrophobic interaction,hydrogen bonding,andπ-πinteraction,wherein the hydrophobic effect as dominant.The adsorption behaviour of biochar for p-nitrophenol removal in wastewater was following the pseudo-second-order kinetic model,and the isothermal adsorption process was under the Langmuir model.At 298K,the maximum adsorption amount of p-nitrophenol in wastewater was measured as622.73 mg/g.The thermodynamic study showed that the adsorption of p-nitrophenol by biochar was a spontaneous and exothermic reaction process.In addition,the biochar material displayed excellent regeneration performance.The adsorption capacity of p-nitrophenol reached 485.01 mg/g after seven cycles of regeneration.The blockage of pores and inactivation of surface functional groups were considered as factors affecting the adsorption performance of chemically regenerated biochar.The phoenix leaves were prepared into biochar and used for the removal of p-nitrophenol,which turned the biomass waste into treasure,and the purpose of"treating waste by waste"was achieved.Also,the material had good adsorption and regeneration properties,which had a good application prospect in organic wastewater treatment.（2）A variety of TiO₂ materials were prepared through orthogonal experiments by solvothermal method.The photocatalytic degradation efficiency results of phenol solution were used as the indicator,and the range analysis method was adopted.It was concluded that the temperature of the reaction system was the most critical factor affecting the photocatalytic activity of nano-Ti O2 materials.The Ti O2 material prepared under optimized conditions was quasi-spherical particles with a particle size of about 20 nm and anatase phase.The degradation rate for phenol was 94.10%under 120 min of UV light.The Ti O2 prepared under the optimal combination was compounded with biochar materials,and the effects of the preparation method and calcination temperature on the performance for phenol removal under visible light were studied.It was found that the composites prepared by ultrasonic and high-temperature calcination had higher removal performance of phenol.Increasing the calcination temperature is conducive to improving the adsorption performance of the carbon materials and thus improving the phenol removal performance of the composite materials.In the prepared composite materials,the sample composite of ultrasonic-combined Tibiochar at 800°C calcination showed excellent removal performance of phenol.The removal rate of phenol was 89.60%.Ti O2 and biochar composite for phenolic pollutant removal achieved an effective combination of photocatalytic technology and adsorption technology,provided a new technique for the treatment of organic wastewater.The pollutants adsorbed on the surface of the composite were photo-degraded at the same time of adsorption,which significantly improved the recyclability of the material,thereby increased the practical application value.