Heavy metals exist in water and soil for a long time and are difficult to degrade. They will accumulate in plants, animals and even human body along with the ecological cycle, thus causing human poisoning and endangering health. In order to reduce the harm, it is very important to control the first pass of heavy metal pollution, that is, it is necessary to treat wastewater containing heavy metals in time and effectively. Material adsorption is an effective way to remove heavy metals. Compared with other adsorbents, functional silica gel can not only effectively adsorb heavy metal ions through coordination, but also has the characteristics of easy separation, reusability and strong stability. It has become the most potential and widely used heavy metal adsorbent in environmental science. However, with the change of functional groups on silica gel, the types and capacities of heavy metal adsorption are different. Therefore, with the development of each functional silica gel adsorbent, it is necessary to explore its performance in different heavy metal adsorption. Nitrogen can coordinate with some heavy metal ions and has high adsorption performance. There are various functional groups of nitrogen ligands. In recent years, the separation and enrichment materials with nitrogen ligands as functional groups have been widely studied.
Lead (PB) is a kind of common toxic heavy metal, which often appears in the waste water produced by machinery, metal, battery, electroplating, coating, paint and other industries. With the discharge of the waste water, it is easily enriched in various biological tissues, and then absorbed by the human body through the skin, digestive tract and respiratory tract, and has adverse reactions with various organs. If the lead content of human body is more than 0.1 mg / L, it is easy to cause anemia and damage the nervous system. In order to solve the problem that the content of heavy metal lead in water pollution exceeds the standard, researchers have carried out a lot of research on it at present. For example, balela and others use natural hydrophobic kapok fiber modified polyacrylonitrile (Pan) to absorb Pb2 + ions from water solution, soak kapok pan nanocomposites in sodium hydroxide solution for hydrolysis, which can significantly improve the adsorption capacity of Pb2 + (78.34 mg / g). At present, the main method to remove lead ions is adsorption method. Generally, adsorption materials with large specific surface area or special functional groups are used. However, the preparation steps of these materials are tedious and the preparation cost and conditions are high. Therefore, a cheap and practical material is urgently needed.
In this paper, aminopropyl bonded silica gel (monoamine, sio2-n) and ethylenediamine-n-propyl bonded silica gel (diamine, sio2-2n) were prepared by one-step reaction of heterogeneous ammoniation. Two-step reactions were carried out to prepare divinyltriamine bonded silica gel (triamine, sio2-3n), triethylenetriamine bonded silica gel (tetramine, sio2-4n), tetravinylpentamine bonded silica gel (pentamine, Sio2-5n, pentavinylamine bonded silica gel (hexamine, sio2-6n) and polyethyleneimine bonded silica gel (polyamine, sio2-nn). The adsorption properties of these seven bonded silica gels for Pb2 + were also studied.
Synthesis of 01 amino silica gel
Synthesis of chloropropyl bonded silica gel (sio2-cp)
300 g of SiO2 was placed in 1000 ml of 6 mol / L hydrochloric acid and mechanically stirred at 60 ℃ for 6 h. After the reaction, it was washed with distilled water for many times to neutral and dried in a blast drying oven to obtain acidified silica gel. The acidified silica gel was activated in a vacuum drying oven at 130 ℃ for 3 h to obtain the activated silica gel.
Weigh 30 g of activated silica gel, put it into a 250 ml four port round bottom flask, add 100 ml of re evaporated toluene and 35 ml of cptes, and reflux reaction under mechanical agitation for 24 h. After the reaction is completed, cool and filter, wash with 30 ml of toluene, 30 ml of ethanol and 30 ml of ether successively, and dry in vacuum at 60 ℃ for 6 h to obtain the final product.
Synthesis of a series of amino bonded silica gel
Weigh 10 g of activated silica gel, put it into a 100 ml four port round bottom flask, add 50 ml of re evaporated toluene, 12 ml of APTES or 12 ml of ethylenediamine-n-propyltrimethoxysilane, reflux reaction under mechanical agitation for 24 h, wait until the reaction is completed, cool and filter, wash with 30 ml of toluene, 30 ml of ethanol and 30 ml of ether successively, and dry in vacuum at 60 ℃ for 6 h, Finally, aminopropyl bonded silica gel and ethylenediamine-n-propyl bonded silica gel were obtained.
Other series of amino bonded silica gel synthesis routes refer to the relevant literature, and make appropriate modifications, the specific steps are as follows.
Weigh 10 g of dry sio2-cp, put it into a 250 ml four port round bottom flask, add 100 ml of re evaporated toluene, 1.3 ml of 9.23 mol / L deta, 1.96 ml of 6.31 mol / L triethylenetetramine, 2.40 ml of 5.01 mol / L triethylenetetramine, 3.09 ml of 3.88 mol / L triethylenetetramine or 0.60 ml of 0.02 mol / L polyethylenimine, reflux for 24 h under mechanical agitation, cool and filter after reaction, Wash with 30 ml water, 30 ml ethanol and 30 ml ether in turn, and dry in vacuum at 60 ℃ for 6 h to obtain corresponding series of amino bonded silica gel. The preparation route is shown in Figure 1.
Fig. 1 synthesis route of series of amino bonded silica gel
Fig. 1 Synthesis of a series of the amino bonded silica gel
SiO2-N: aminopropyl bonded silica gel; SiO2-2N: ethylenediamine-N-propyl bonded silica gel; SiO2-3N: diethylenetriamine bonded silica gel; SiO2-4N: triethlenetetramine bonded silica gel; SiO2-5N: tetraethylenepentamine bonded silica gel; SiO2-6N: pentaethylenehexamide bonded silica gel; SiO2-nN: polyethyleneimine bonded silica gel.
02 for the detection of Pb2 + in the actual wastewater, accurately weigh 3 parts of 160mg sio2-2n to 3 50ml centrifuge tubes, add 20ml of wastewater containing Pb2 + respectively, shake in a shaker at 30 ℃ for 10h, centrifuge at 4200 R / min for 5min, take 2ml of solution, add 10ml of boric acid potassium chloride buffer solution with pH = 9, shake well, add 5.0ml of trichloromethane solution containing 0.05g of dithizone, shake violently for 1min, after standing and layering, The chloroform layer was filtered into a 1 cm cuvette and the absorbance value was measured at 510 nm.
China Chemical Society:
http://www.ccspublishing.org.cn/article/doi/10.3724/SP.J.1123.2019.09030
China HowNet:
https://kns.cnki.net/KCMS/detail/21.1185.O6.20200220.1721.020.html
Contents of Volume 38, issue 3 of previous excellent journal of chromatography
Application of molecularly imprinted polymer in the determination of antibiotic residues
Enrichment and identification of n-phosphorylated modified proteins
[special issue of women scholars] Research Progress in analytical methods of perfluorinated / perfluorinated compounds
Research progress of supramolecular macrocyclic compounds for dye adsorption
Research progress of pretreatment methods for mycotoxins in food
Research progress in separation and analysis of chiral compounds by capillary electrophoresis
[special issue of women scholars] in situ solvothermal polymerization of metal organic framework / nitrogen carbide nano coated solid phase microextraction fiber for high sensitive detection of pesticide residues in black tea
[special issue of women scholars] monitoring the chemical synthesis of human atrial natriuretic peptide by ultra high performance liquid chromatography mass spectrometry