Purification And Application Of Fulvic Acid And Humic Acid From Sludge Compost

Fulvic acid and humic acid are macromolecular mixtures widely found in the surface environment of nature.They contain a large number of reactive groups with acidic,hydrophilic,interfacial,ion exchange,adsorption and complexing properties.They are important factors affecting the ecological environment.The structural composition of fulvic acid and humic acid has not yet been clarified,and a full understanding of the structural composition of fulvic acid and humic acid will help to understand its environmental effects.In this paper,aerobic composting was carried out using municipal sludge and leaves as raw materials.Fulvic acid,humic acid and humin were extracted from the compost by the alkali dissolution and acid extraction method.Subsequently,XAD-8macroporous resin method,four-stage membrane separation method and water washing purification method were used for classification and purification.Fulvic acid could be divided into six components by ultra-high performance liquid chromatography-mass spectrometry.The molecular weight and chemical formula of each component of fulvic acid are analyzed,and the chemical structure is reasonably speculated.Finally,humic acid and humin were used as adsorbents,the adsorption of humic acid and humin on Cu²⁺,Cd²⁺,Pb²⁺,Zn²⁺was studied.The main conclusions are as follows:The XAD-8 macroporous adsorption resin method is an effective method for purifying fulvic acid.The four-stage membrane separation method can classify fulvic acid into four fractions according to the molecular weight.Fulvic acid and humic acid are mainly composed of C,H,O and N.And their molecular structures contain a large number of aromatic structures,-OH bonds,and oxygen-containing functional groups.¹³C nuclear magnetic resonance(¹³C NMR)shows that carbon in humus mainly existed in the form of aliphatic carbon,aromatic carbon and carboxylic carbon.X-ray photoelectron spectroscopy（XPS）shows that there are seven chemical forms of carbon,four chemical forms of nitrogen and two chemical forms of oxygen on the surfaces of fulvic acid,humic acid and humin.The results of thermal analysis（DSC/TG）show that humus have exothermic peak.The specific surface area（BET）analysis show that the specific surface area of humus are small.High performance liquid chromatography（HPLC）can effectively separate fulvic acid.The effects of mobile phase,column,temperature,elution mode and sample solvent on the separation were studied.Under the positive ion detection mode,fulvic acid was separated into six single compounds by ultra performance liquid chromatography-time of flight-quadrupole-mass spectrometry（UPLC-TOF-Q/MS）.Humic acid and humin can effectively adsorb Cu²⁺,Cd²⁺,Pb²⁺and Zn²⁺.Adsorption time,reaction temperature,p H,initial concentration of heavy metal ions and the amount of adsorbent have significant effects on the adsorption process.Under the conditions of reaction temperature of 25℃,p H of 2.0,reaction time of 6 h,and the amount of adsorbent of 2.5 g.The removal rate of Cu²⁺,Cd²⁺,Pb²⁺and Zn²⁺at a concentration of 100 mg/L was 91.47%,85.14%,98.61%,69.71%,respectively.