Preparation Of Wood-based Absorbents And The Study On Purification Of Water Pollutants

The pollution of heavy metal and oily wastewater has become an urgent environmental problem.The surface of wood fiber material is rich in hydroxyl,carboxyl and other active groups,and has a certain adsorption capacity.With its high specific surface and chemical modifiable properties,the functional construction of its surface is carried out to prepare efficient and low-cost biological adsorbents,which is of great significance in water pollution treatment.This paper focuses on the adsorption of heavy metals,oils and organic solvents in water by high value utilization of wood materials.The preparation of modified wood powder and the construction of hydrophobic surface of cellulose aerogel were completed by using abundant agricultural and forestry biomass resources.At the same time,the structure,morphological characteristics,thermal stability and adsorption performance of the adsorbed materials were discussed by means of experiments,physical and chemical tests,model fitting and other analysis methods.The main research contents were as follows.(1)In the preparation of bio-based adsorbents from wood processing residues,wood based adsorbents rich in amino functional groups were prepared by using the high adhesion characteristics and chemical versatility of plant polyphenolic tannic acid and the"two-step"co-deposition method.The FTIR,X-ray photoelectron spectroscopy(XPS)and other test methods showed that the amino chain segment containing catechenol was successfully introduced.(2)The modified saw powder can effectively remove Cd(II)from water,and its adsorption capacity is up to 22.66mg/g,156 times that of original wood powder.The initial concentration of ions,temperature,adsorption time and pH of the solution all have certain effects on the removal of Cd(II).The results showed that the pH significantly effect the removal of Cd(II)from modified saw powder.As the pH value increased from 2.0 to6.0,the removal rate of Cd(II)was on the rise.When the initial concentration was 50mg/L and the pH was 6.0,the removal rate of Cd(II)was up to 65%.The XPS,FTIR,X-ray spectrum(EDX)and other characterization confirmed that the saw powder adsorbent was mainly used to remove metal ions through coordination chelation of amino and catechiol functional groups anchored on the surface with Cd(II).(3)The uneven pore diameter distribution and low specific surface area of the saw powder are still the dominant factors restricting its adsorption performance.The high length-diameter ratio of cellulose nanofibers(CNFs)can form aerogel with three-dimensional porous shape,which has advantages in the field of adsorption.With the help of biomimetic silanization strategy,long-chain siloxane prepolymer and tannic acid molecules can be co-deposited on the surface of CNFs,and a full bio-based aerogel material with low density(15.5 mg/cm~3)and high porosity(0.01cc/g)can be prepared through freeze drying process.The surface microstructure of CNFs was characterized by FTIR,TGA and TEM,and the results showed that the catechol functional groups on the surface of CNFs made long-chain siloxane(derivative of cashew phenol)bond through covalent bond and hydrogen bond,giving the aerogel higher hydrophobic property(water contact Angle up to 121°).In addition,the polyphenols remaining on the surface provide abundant chelating sites for heavy metal ions.The adsorption properties and the influencing factors and the mechanism of aerogel were evaluated.The maximum adsorption capacity of Cu(II)in water was 45.6 mg/g by modified aerogel with 0.2 g siloxane addition.When pH=5 and the initial concentration of Cu(II)in the simulated wastewater was 50 mg/L,the highest removal rate of Cu(II)by aerogel was 89.65%.The adsorption behavior of Cu(II)was consistent with the quasi-second-order kinetic adsorption model and the Langmuir isothermal adsorption model.The results of oil and organic solvent adsorption experiments showed that the maximum absorption capacity of aerogel to chloroform was up to 108 g/g,and the adsorption process was controlled by internal and external diffusion.