Method for in-situ passivation of cadmium pollution in rice field soil by using bottom ash from agricultural and forestry biomass direct-fired power plants

Abstract

The invention relates to a method of passivating cadmium pollution in a rice field in situ by bottom ash of an agriculture and forestry biomass direct-fired power generation plant. The cadmium pollution in the rice field in situ is passivated by using a composite material formed by the bottom ash of the agriculture and forestry biomass direct-fired power generation plant, animal carbon and bentonite as a repairing agent. Compared with biomass ash which is independently used, compounded with the animal carbon, the cadmium fixing ability of the material is improved obviously. By applying the repairing agent to repair the cadmium polluted land, the effect is obvious. The maximum adsorption amount of cadmium in solution by the repairing agent is 34.8 mg / g. After applying the repairing agent which is over 5 kg / m<2> to the in situ cadmium polluted soil, the soil cadmium passivating effect is obvious and the cadmium content in effective state is reduced obviously. By inputting the repairing agent at one time, the cadmium content in early season rice is reduced by 60% or above in a same year, and the cadmium content in late rice is reduced by 57-73%. Compared with a blank control group, the effective silicon content of soil of a blot with the repairing agent is enhanced obviously, and the plant height of rice is increased.

Description

technical field [0001] The invention belongs to the technical field of soil cadmium pollution control, and in particular relates to a method for in-situ passivation of cadmium pollution in paddy field soil by using the bottom ash of agricultural and forestry biomass direct combustion power plants. Background technique [0002] The "National Soil Pollution Survey Bulletin" jointly issued by the Ministry of Environmental Protection and the Ministry of Land and Resources in 2014 shows that the overall situation of my country's soil environment is not optimistic. The soil pollution in some areas is relatively serious, and the quality of cultivated land soil environment is worrying. The survey shows that the total excess rate of soil pollution in my country is 16.1%, and the main types of soil pollutants are inorganic substances. Among the eight kinds of inorganic substances investigated, cadmium has the highest rate of excessive limit, reaching 7.0%. The exceeding range is large....

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Problems solved by technology

[0007] The biomass power plant involved in the above-mentioned patent is a broad concept. Waste-to-energy power generation also belongs to the category of biomass power generation. However, the heavy metal content in the ash obtained from waste-to-energy power generation usually exceeds the standard and cannot be used as a repair agent.

In addition, the above-mentioned patent needs to grind the ashes of agricultural and forestry biomass direct-fired power plants, and then carry out processing steps such as screening, and the particle size is required to be between 180-220 mesh (about 70-80 μm), and the disadvantages are obvious: (1 ) has strict requirements on grinding and screening equipment, which is not conducive to reducing the production cost of restoration agents

(2) The particle size of 70-80 μm of biomass ash is too small, it is easy to be affected by natural factors such as wind force and precipitation during the application process, which makes it inconvenient to add in engineering application and easily causes loss

(3) If the particle size of biomass ash is too small, there is a risk of blocking soil voids and reducing soil permeability

[0008] It should also be pointed out that the above-mentioned patent uses the ashes of agricultural and forestry biomass direct-fired power plants alone for cadmium pollution remediation, and its remediation efficiency is obtained based on pot experiments, and it is not known whether it is applicable to in-situ site remediation

In addition, the restoration effect of the above-mentioned patents only utilizes the adsorption effect of the ashes of agricultural and forestry biomass direct-fired power plants, and does not consider the positive effect of the release of silicon components in the power plant ash to increase the available silicon content of the soil

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