Study On Preparation Of Biochars Produced From Different Types Of Feedstocks And Their Adsorption Properties For Methylene Blue

With the rapid growth on economy and global population,the increasing energy demand leads to the scarcity of fossil fuels and other resources,while the environmental problems is getting more and more serious.Biomass is a kind of renewable energy source and has many advantages such as easy to store and transport,large variety and quantity,and low cost.As a class of famous carbon materials,biochars prepared from biomass present great potential in waste water treatment and soil improvement because of their excellent physical and chemical properties and diversity functions.In this paper,three kinds of biomass including municipal sludge,garden waste and corn stalk in Dalian area were used as raw materials.The effects of different pyrolysis temperature,carbonization time and heating rate on the production rate and p H of biochars were investigated.Instrumental analysis techniques were used to characterize the morphology,surface functional groups and crystal structure of biochars,and their adsorption properties for methylene blue were also studied in detail.The main research results obtained are as follows:（1）The effect of pyrolysis temperature on the yield of three kinds of biochars is significant,but the effects of carbonization time and heating rate are not obvious.Under the same pyrolysis conditions,the yield of sludge biochar is higher than that of garden waste and corn stalk biochar.The p H of the three biochar is in the range of 7.27～9.98,the value order is:corn stalk biochar>garden waste biochar>sludge biochar.（2）Scanning electron microscope analysis results show that the suitable conditions for pore formation are about 500℃,longer pyrolysis time,and lower heating rate.Garden and straw biochars show clear tubular pores,and the pores on sludge biochar is disordered and irregular.The results of Fourier infrared spectroscopy analysis show that higher pyrolysis temperature lead to less polar functional groups and more aromatic ones with higher stability for all three kinds of biochars.Functional groups in garden and straw biochars are more abundant than that of sludge biochar.X-ray diffraction analysis results indicate that the pyrolysis temperature has no obvious effect on the crystal structure of sludge biochar,in which the inorganic components are mainly quartz and aluminum phosphate.However the increase of pyrolysis temperature makes the diffraction peak of cellulose in garden and straw biochar weaker,the ones of Ca CO₃stronger,and the graphitization degree higher.（3）The adsorption ability of plant sources biochars is better than that of sludge biochar,and the adsorption capacity of three biochars for methylene blue is 24.54～24.83 mg·g^-1,and the removal rate is 7.3%～65.5%.The garden waste biochar has the best adsorption performance prepared by carbonized for 4 h at 700℃with the heating rate of 5℃/min.The adsorption capacity of the prepared biochar（0.1g）for methylene blue solution(50 mg·L^-1)is24.83 mg·g^-1,and the removal rate is 65.5%after shaking for 4 h.In summary,the stability of biochar can be achieved through reasonable control of pyrolysis conditions.The three biochars have a certain adsorption effect on methylene blue in wastewater.The development of biochar is of great significance for mitigating environmental pollution and achieving resource recovery and utilization of biomass waste.