Abstract: In order to solve the problem that there are many oxygen-containing functional groups on the surface of low-rank coal and the separation effect of traditional flotation agents is poor,the low rank coal flotation experiment was carried out by using the anionic surfactant SDBS as flotation promoter.By single factor condition test,the suitable range of diesel oil and SDBS dosage were determined to be 6-9 kg/t and 800-1 500 g/t respectively,and the ratio of sec-octanol to diesel oil dosage was 1 ∶ 10-1 ∶ 5. On this basis,the response surface method was used to optimize the amount of diesel,sec-octyl alcohol and SDBS.The optimization test results show that there is an interaction among diesel,sec-octyl alcohol and SDBS,and the main effect relationship was as follows: SDBS>diesel>sec-octyl alcohols,and the second order regression equation with flotation perfect degree as the response values is obtained,which determines the best dosage of diesel,sec-octyl alcohols,SDBS to be 8. 57 kg,1. 28 kg/t,1 307 g/t,respectively.At this time,the theoretical value of the flotation perfect degree is 24. 16%.Under the condition of the optimal dosage of reagents,the flotation experiment was carried out. The obtained flotation perfect degree is 23. 98%,which is consistent with the theoretical value of the response surface methodvalue.The results show that the response surface method used to optimize agent system is accurate and feasible.The XPS wide-range scanning test results show that the oxygen-carbon ratio on the surface of low-rank coal is 1.40%.After adsorbing SDBS,diesel oil and diesel oil+SDBS,the oxygen-carbon ratio decrease to 1. 26%,1. 12% and 1. 01%,respectively.XPS C1 s analysis results show that the content of C—C/C—H group on the surface of low-rank coal is 66. 47%.After adsorbing SDBS,diesel oil and diesel oil+SDBS,the oxygen-carbon ratio increase to 72. 60%,75. 13%and 77. 12%,respectively.Before and after adsorption,the content of oxygen-containing functional groups on the surface of low-rank coal decreases significantly,the content of C—O group decreases from 16. 59% before adsorption to 15. 71%,14. 66% and 12. 71%,the content of C O group decreases from 10.09% to 7. 70%,4. 23% and 5.64%,and the content of O C—O group decreases from 6. 85% to3. 99%,5. 98% and 4.54%,respectively.The XPS test results show that the combined use of diesel and SDBS is better than that of diesel and SDBS alone.When SDBS as promoter,the content of C—C/C—H groups on the surface of low rank coal increases and the content of oxygen containing functional groups decreases,which indicates that the hydrogen bonding adsorption is the main physical adsorption of SDBS on the surface of low rank coal,the effective implementation of oxygen containing functional groups in low rank coal surface is realized,at the same time,C—C/C—H groups of SDBS expose on the surface of low rank coal enhance the hydrophobicity of low rank coal surface,which helps improve the flotability of low rank coal slime.