Investigation On Preparation Of Biochar And Its Application In Soil Improvement And Treatment

The yield of straw and other biomass is very large every year.However,the traditional utilization of biomass has following problems.On the one hand,it causes a lot of waste of resources,on the other hand,it brings serious environmental pollution.At the same time,the soil quality in our country continue to decline,and the organic pollution is especially serious.As a new type of soil additive,the application of biochar carbonized from waste straw biomass is not only an effective use of straw resources,but also provides a new choice for solving problems of soil.Therefore,it is of great significance to investigate preparation process of biochar from biomass and applying it in soil improvement and treatment.The main research work of this topic is as follows:(1)Biochar was prepared by using high temperature resistance furnace with different biomass sources(wheat straw,soybeans straw and corn straw)under various reaction temperature(400 ??500 ??600 ??700 ?)and pyrolysis time(30 min?60 min?120 min?180 min?240 min).Its physical and chemical properties such as ash,pH value,surface morphology,surface functional groups,phase,specific surface area,particle size and elemental content and other properties were tested to examine the impact of various pyrolysis conditions on the quality of biochar.(2)Ryegrass was planted at room temperature of 25?,relative humidity of 49%and light duration of 16 h/d with different kinds of biochar(apricot shell biochar,rice husk biochar,pine charcoal purchased and wheat stalk biochar,soybean stalk biochar and corn stalk biochar obtained at 500? for 2 h)to carry out soil improvement experiment.And the rhizosphere soil was collected at different periods of cultivation(1,2,3,and 4 weeks of ryegrass emergence).On this basis,the dynamic changes of enzyme activity in the process were analyzed to compare the effect of different biochar on soil enzyme activity.(3)Taking the representative of PAHs-naphthalene as research object,soil remediation experiments were carried out.During different adsorption time,change the types of biochar(same as ryegrass pot experiment)and dosage of biochar(mass ratio with soil is:0.2%,0.5%,1%,1.5%and 2%)and analyze the adsorption characteristics of organic pollutants from different biochar as well as the dynamic response characteristics of the bioavailability of pollutants in the processThrough the above experimental study,the main conclusions are as follows:(1)It was discovered in the characterization experiment that the physical and chemical properties of biochar will be different due to the changes of their biomass materials and pyrolysis parameters.As a result,biochar prepared at 500? for 120 min will have better quality,such as larger specific surface area,higher pH value and SEM imaging with the characteristics of rich pores than those with other pyrolysis conditions.(2)In the pot experiment of ryegrass,it found that soil invertase activity was positive correlated with the time that biochar was added to the soil.When ryegrass grew for 4 weeks,the activity of invertase increased from 20%to 83%,the promoting effects of biochar on invertase activity were:pine charcoar>soybean straw biochar>apricot shell biochar>rice husk biochar>wheat straw biochar>corn stalk biochar.The maximum rate of soil urease activity appareed when the ryegrass was cultivated 3 weeks.Among them,the group that added wheat straw biochar had the maximum value of urease activity promotion rate:64.76%.The growth rate of urease in the groups adding the other five biochars ranged within 21.71%to 49.38%.(3)In the experiment of adsorption effect of naphthalene in soil on biochar,whether adsorption time or biochar dosage as a variable,pine charcoal has obvious advantage for adsorbing naphthalene.When adsorption time was 48 h,the amount of adsorption and biochar dosage showed a positive correlation.When biochar dosage was 2%,pine charcoal had the strongest naphthalene removal rate of 90.29%.The removal rates of naphthalene in soils were 61.94%?87.81%?46.24%?66.53%and 61.73%,respectively,with addition of apricot shell biochar,rice husk biochar,wheat straw biochar,soybean straw biochar and corn stalk biochar.When biochar dosage was 0.5%,the adsorption efficiency of biochar increased with the increase of adsorption time.When the adsorption time was 48h,the group of adding pine charcoal had the maximum removal rate of naphthalene of 88.65%.The removal rates of naphthalene in soils were 50.45%,87.14%,37.83%,62.75%and 54.74%,with the addition of apricot shell biochar,rice husk biochar,wheat straw biochar,soybean straw biochar and corn stalk biochar respectively.