| In recent years, food safety incidents soil cadmium pollution caused by frequent non-poor,find a safe and reliable remediation of cadmium contaminated soils repair agent imminent.Biochar as an environmentally friendly and significant effect modifier attracted widespread attention. But on different biochar modified physicochemical properties, research on cadmium adsorption characteristics there are different conclusions, which may be related to the nature of biochar. This thesis chooses corn cobs, corn stover and wood chips as raw materials, select400℃, 500℃, 600℃ and 700℃ as the final pyrolysis temperature, and the use of modified and modified by microwave Na OH solution of two different methods for preparing the modified organism charcoal, then study the physicochemical properties, adsorption properties and mechanisms of different types of biochar screened for cadmium adsorption biochar good varieties of pot experiment, which studies the impact modified biochar on soil physical and chemical properties, reducing soil effect and reduce the amount of crops to absorb cadmium cadmium content.The main findings are as follows:Biochar different physico-chemical properties 1. different pyrolysis temperatures preparation, heating rate, pyrolysis temperature, etc. will affect the modification process for preparing biochar physicochemical properties. Biochar yield with increasing pyrolysis temperature decreases, wherein the C content, ash content, specific surface area and porosity but rises with increasing temperature, the temperature rises causing the p H to increase also will biochar Big. Under the same raw materials and conditions of pyrolysis temperature, microwave modified biochar C, H, N, S and other elements were higher than other treatments. After sodium hydroxide modified in biochar production, aperture, and other indicators of the basic group compared to the unmodified biochar have raised, since the Na OH particles attach biochar surfaces, resulting in reduced specific surface area. 700℃ corn stover biochar than the other 35 kinds of biochar, has a large specific surface area(131.57m2 / g) and the minimum aperture(2.08nm). After Na OH modified, the total number of biochar basic groups are compared with other methods 103.51-418.37% increase, lactone group number is less, the number of carboxyl30.27%-133.73% decline in the total number of acidic groups are 1.77%-35.56% decrease.2. The test found that after Na OH solution modified biological carbon adsorption is better,where corn stover biochar with Na OH at 600℃ conditions Modification of Cd adsorption best,up to 78.7mg / g, the modified biological carbon adsorption of Cd than the unmodified biochar increase 2.3-7.6 times; when the adsorption time reaches 50 min, biological carbon adsorption of Cd basically balanced; the solution p H around 7, biochar Cd adsorption rate of up to 80%. Thus,corn stover-600℃-Na OH biochar adsorption capacity, fast adsorption rate characteristics, to better treatment of contaminated water.3. Applying biochar in soil can not only improve soil, improve soil nutrients and reduce the cadmium content in the soil, but also increase crop yields, reduce the amount of crop so absorbed cadmium. After biological charcoal, ground fresh weight with cabbage biochar is added to increase the growth rate of 1.4 to 25.3%, 5% 600℃ by adding Na OH modified wood biochar increase crop fresh weight of the best, growth rate of 25.3%; cabbage aboveground amount of Cd content increases as the added amount of biochar significantly reduced compared to the control group, a drop of 25.3% in the control group of Chinese cabbage in the amount of Cd content was0.76 mg / kg; in addition, adding biochar cause soil potassium, nitrogen, phosphorus, organic matter content increases, can also improve soil CEC and used to improve acidic soils.Na OH-modified 600℃ wood biochar at 5% addition, can inhibit crop uptake Cd, increase crop yield, improve soil compared to other aspects of treatment have better results. |
PDF Full Text Request