Study On The Utilization Of Wheat Straw As A Resource And Its Products' Adsorption And Treatment Effect On Water Pollutants

At present,the water environment is mainly faced with two major problems:eutrophication and heavy metal overdose,and most of the water bodies are compound polluted water bodies.Adsorption is an effective technique to control environmental pollution.It is often used in eutrophicated water government,and can also be used to remove heavy metals in water.The adsorption method has the advantages of high efficiency and less secondary pollution.China is rich in wheat straw resources,and the utilization of agricultural wheat straw waste through the resource is relatively small.This paper takes wheat straw as raw material to explore the utilization technology of wheat straw resources.The feasibility of synthetic synthetic zeolite from wheat straw was investigated by hydrothermal synthesis method and biochar from wheat straw was prepared by continuous pyrolysis at low temperature.Using biochar for Cr⁶⁺ and PO₄^3- polluted water for adsorption,mainly analyzes the biochar categories,types of pollutants concentration,pollutants（single and compound pollution）,initial solution pH value,adsorption temperature on the influence of the biological carbon adsorption effect,at the same time,through dynamic model fitting,isothermal curve fitting model to explore the biological carbon under different conditions on the adsorption mechanism of Cr⁶⁺ and PO₄^3- .The main conclusions are as follows:Using wheat straw making synthetic zeolite,when low activation temperature of 400℃,the hydrothermal synthesis of generating crystal,when the activation temperature is 600℃,activation time of 1h,lye material for 2 mol/L NaAlO₂ solution,the crystallization temperature is 80 ℃,the crystallization time of 12 h,wheat straw can synthesize the type A zeolite with high purity,but lower crystallinity and crystal is not stable.When using wheat straw to prepare biochar,the pore structure of biochar increased with the increase of the preparation temperature,the total pore volume first decreased and then increased with the extension of the preparation time,and slowly increased with the increase of the preparation temperature until reached a stable state.Biochar has a large number of functional groups on its surface,mainly C≡C,C=O,C-O,and aromatic C-H bonds.Biochar has a good removal efficiency for CrO₄^2-.In single CrO₄^2-polluted water body and composite CrO₄^2-and PO₄^3- polluted water body,the removal rate of CrO₄^2- by biochar reaches more than 90%.In single polluted water body,the removal rate decreases with the increase of pollution concentration,but in compound polluted water body,the removal rate decreases with the increase of pollution concentration.The removal efficiency of PO₄^3- increased with the increase of preparation temperature and time,but decreased with the increase of PO₄^3- concentration.The adsorption rate of biochar for CrO₄^2-in the composite polluted water body was slightly different from that in the single polluted water body,both adsorption rates were 6 h,but the adsorption equilibrium amount increased from 743.24 mg g^-1 to 863.31 mg g^-1.Both adsorption rates were combined quasi-secondary kinetic models.Biochar reached the adsorption equilibrium at about 4h in a single po43-polluted water body,while the adsorption equilibrium time increased to 3 h in a compound polluted water body,and the adsorption equilibrium amount increased from 255.76 mg·g^-1 to 294.09 mg·g^-1,indicating that the presence of CrO₄^2-and PO₄^3- could enhance the adsorption performance of biochar on each other.The adsorption performance of biochar for CrO₄^2-increased with the increase of adsorption temperature in the two polluted water bodies.However,in the single CrO₄^2-polluted water body,the adsorption process was endothermic reaction and adsorption isothermal composite Freundlich model,while in the complex polluted water body,the adsorption process was exothermic reaction and adsorption isothermal composite Langmuir model.The adsorption performance of biochar for PO₄^3- in two polluted water bodies increased with the increase of adsorption temperature,and both were endothermic reactions.The adsorption process could be well fitted by Langmuir model.