Study On The Relationship Between The Surface Chemical Structure And ? Potential Of Deashing Coal

The flocculation efficiency of coal slime water is essentially determined by the chemical structure of coal itself.It is of great significance to study the chemical structure of coal to improve the treatment efficiency of slime water.The strong negative electricity on the particle surface makes the slime water difficult to settle,which is especially prominent in the low-rank coal slime water.Based on the chemical structure of coal itself,it is one of the key problems to study the cause of coal surface electronegativity and its influencing factors to improve the efficiency of slime water treatment.In this paper,the chemical structure of different rank coal is analyzed by potentiometric titration and ? potential test.The structural parameters of coal are determined by 13C-NMR,and the relationship between structural parameters and IEP is analyzed.At the same time,the molecular model of coal is constructed,and the relationship between the chemical structure of coal and ? potential is analyzed from the micro level by using quantum chemistry and molecular dynamics calculation.The reason of high ? potential of some slime water is explained,which provides theoretical basis for the treatment of difficult to settle slime water.Through 13C-NMR analysis,it is found that all coal samples mainly include aromatic carbon and aliphatic carbon.With the increase of coal rank,the proportion of aromatic carbon increases gradually.At the anthracite stage,almost all carbon atoms exist in the form of aromatic carbon.The IEP decreased with the increase of faC and falO.The increase of f'a,faH and faB means the decrease of side chain groups and the increase of protonated aromatic carbon ratio in coal aromatic ring structure,which will increase the hydrophobicity and IEP of coal.The binding energy of the oxygen-containing functional model compound to the H3O+ system is around-200 kJ/mol,far more than weak interactions between molecules.The Mayer bond between H3O+ and oxygen-containing functional groups exceeds 0.5,and the basin-space integral of the electron localization function(ELF)is 2,that is,the adsorption of H3O+ by coal is mainly based on chemical adsorption.It is found that the negative potential caused by the ? electron cloud is superimposable,so the binding energy between the aromatic nuclear structure model and H3O+ increases with the number of benzene rings.It also shows that the high rank coal is easier to adsorb H3O+.Based on the 13C-NMR test results,structural unit models of coal are constructed,and the surface electrostatic potential are analyzed.It is found that the extreme points of the electrostatic potential of long-flame coal and gas coal are mainly distributed near the oxygen-containing functional groups,while the extreme points of coking coal and anthracite are distributed near fused ring aromatic hydrocarbons.With the rise of coal ranks,the area of non-polar areas on the surface of coal structural units has increased from 39.68%to 52.40%.Water molecules exist on the surface of coal as a single molecular layer;although there is no obvious adsorption layer structure of H3O+,there is still a large density near the interface.Water molecules are easy to diffuse into long-flame coal and gas coal,while there are almost no water molecules in coking coal and anthracite.The average hydrogen bond length between water molecules is 1.77 A,which basically has nothing to do with H3O+and coal type.H3O+can destroy the original semi-ordered structure in the water body.In the acid environment,the stability of the hydration membrane structure on the coal surface is reduced.When the water molecules are not enough to cover the coal surface,it is preferentially adsorbed on the oxygen-containing functional groups and the model surface with a lower z value.When the number of water molecules exactly covers the model surface,the coal surface will gradually form a hydration film structure.The initial stage of the formation of the hydration film on the coal surface is mainly the hydrogen bond function between the oxygen-containing functional groups and water molecules on the surface.Low-rank coal has more polar groups and is more prone to hydration.After the coal surface begins to form a hydration film,the subsequent increase in thickness of the hydration film is mainly due to hydrogen bonding between water molecules.The paper has 31 pictures,20 tables,and 115 references.