Effect of humic acid on equilibrium adsorption of water of Shengli lignite
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摘要: 研究了褐煤中重要的成分腐殖酸对褐煤水分的影响。测定了内蒙胜利褐煤中腐殖酸含氧官能团的含量，并分析了褐煤、棕黑腐殖酸和残余煤的等温吸附和脱附曲线。通过Dent吸附等温模型研究了褐煤和棕黑腐殖酸第一层吸附和第二层吸附。结果表明，胜利褐煤2/5羧基和1/5羟基是由腐殖酸提供的。棕黑腐殖酸相对褐煤孔径和孔容较小，不利于水簇的形成。腐殖酸对褐煤的复吸水是不利的。Abstract: The effect of humic acid, an important component of lignite, on the water content in Shengli lignite was studied. The content of oxygen containing functional groups of humic acid in Shengli lignite was determined. The isothermal adsorption and desorption curves of the lignite, brown humic acid and the residual coal were analyzed. Further the primary and secondary site adsorption of the lignite, brown humic acid and the residual coal were studied. The results show that 2/5 carboxyl and 1/5 hydroxyl in Shengli lignite are provided by humic acid. The pore size and pore volume of brown humic acid are smaller than those of the lignite. So brown humic acid is unfavorable for the formation of water clusters. The humic acid is adverse to equilibrium adsorption of water for Shengli lignite.
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Key words:
- lignite /
- humic acid /
- equilibrium adsorption of water /
- isothermal adsorption
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图 1 等温吸附和脱附曲线
Figure 1 Curves of isothermal adsorption and desorption
(a): raw coal; (b): brown humic acid; (c): residual coal
表 1 原煤的工业分析
Table 1 Proximate analysis of the raw coal sample
Proximate analysis w/% Mad Ad Vd FCd Vdaf FCdaf 14.44 16.00 41.19 42.81 49.04 50.96 
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表 2 原煤的腐殖酸含量测定
Table 2 Analysis of humic acid content
Total humic acid w/% Brown humic acid w/% Fulvic acid w/% 30.22 25.64 4.58
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表 3 钠元素含量的测定
Table 3 Analysis of Na
Raw coal w/% Brown humic acid w/% Residual coal w/% 1.00 0.35 17.49
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表 4 含氧官能团的衡算
Table 4 Balance of oxygen containing functional groups
Sample Content w/% Total acidity /(mmol·g-1) Carboxyl /(mmol·g-1) Hydroxyl /(mmol·g-1) Brown humic acid (measure) 25.64 7.32 4.73 2.59 Fulvic acid (measure) 4.58 9.00 7.57 1.43 Residual coal (measure) 69.78 7.16 3.19 3.97 Raw coal (calculation) 100.00 7.29 3.79 3.53 Raw coal (measure) 7.38 3.85 3.50
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表 5 腐殖酸含氧官能团对褐煤含氧官能团的贡献
Table 5 Contribution of oxygen functional groups of humic acid to the oxygen containing functional groups of brown coal
Sample Carboxyl /(mmol·g-1) Hydroxyl /(mmol·g-1) Brown humic acid 1.21 0.66 Fulvic acid 0.35 0.065 Raw coal 3.85 3.53 Contribution of total humic acid 40.52% 20.54%
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表 6 孔容、孔径和比表面积的测定
Table 6 Determination of pore volume, pore size and specific surface area
Sample Pore volume v/(cm3·g-1) Pore size d/nm Specific surface area (BET) A/(m2·g-1) Raw coal 2.59×10-2 35.04 2.95 Brown humic acid 1.31×10-2 5.23 10.00 Residual coal 6.15×10-3 39.94 0.616
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