Study on the mercury removal performance and strengthening method of high sulfur and iron content textile dyeing sludge char
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摘要: 以高硫高铁印染污泥为原料制备热解焦,对热解前后样品中的硫和铁结合态进行了分析,并研究了热解焦对单质汞的脱除特性,进一步的,通过空气氧化、ZnCl2浸渍等手段对热解焦进行改性,提升其脱汞性能。研究结果表明,污泥中的硫主要为硫酸盐、硫化物、有机硫三部分,铁以三价和二价化合物存在。热解后,无机硫向有机硫转化,三价铁向二价铁转化,大部分硫和铁保留在热解焦中,部分生成磁黄铁矿 (Fe1−xS)。污泥原焦比表面积较小,具有一定的脱汞能力,以化学吸附为主导。空气氧化时间控制在12 h以内可以使高温(≥ 600 ℃)热解焦的汞吸附量提升46%以上。ZnCl2浸渍污泥热解制焦,可以进一步固硫生成ZnS,600 ℃热解的ZnCl2改性焦30 min内汞吸附量达到了28.71 μg/g,加以空气氧化,脱汞效率进一步提升,氧化12 h后性能最佳,汞吸附量为43.75 μg/g。Abstract: Pyrolysis char was prepared from high sulfur and iron content textile dyeing sludge. The combined states of S and Fe in the samples before and after pyrolysis and the removal characteristics of Hg0 by pyrolysis char were studied. The performance of Hg0 removal was improved by air oxidation and ZnCl2 impregnation. The results showed that S in sludge was divided into sulfate, sulfide, and organic sulfur. Fe existed as Fe3+ and Fe2+ compounds. After pyrolysis, inorganic sulfur was transferred to organic sulfur and Fe3+ was transferred to Fe2+. Most S and Fe were retained in pyrolysis char and some formed pyrrhotite (Fe1−xS). The specific surface area of raw char was small and had a certain Hg0 removal capacity, dominated by chemical adsorption. When the air oxidation time was controlled within 12 h, the Hg0 adsorption capacity of pyrolysis char at high temperature (≥600 ℃) was increased by more than 46%. During pyrolysis of ZnCl2 impregnated sludge, more S was fixed in pyrolysis char to generate ZnS. The Hg0 adsorption capacity of ZnCl2 modified char pyrolyzed at 600 ℃ reached 28.71 μg/g in 30 min. With air oxidation, the Hg0 removal efficiency was further improved. After oxidation for 12 h, the Hg0 adsorption capacity was 43.75 μg/g.
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Key words:
- textile dyeing sludge /
- pyrolysis char /
- demercuration /
- adsorption
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表 1 污泥及热解焦特性
Table 1 Characteristics of sludge and pyrolysis char
Sample Char yield/% Ultimate analysis w/% Ash wd/% XRF analysis of ash w/% R(S) R(Fe) S/C C S N H Fe2O3 SO3 ZnO Cl C000 − 32.22 10.19 5.15 4.34 32.93 42.30 16.38 1.41 ND 12.35 9.75 0.38 C400 66.33 31.90 13.47 5.47 2.40 43.97 51.36 14.35 2.16 ND 16.00 15.81 0.50 C500 61.92 32.92 13.75 5.22 1.96 48.60 49.92 16.24 2.38 ND 16.91 16.98 0.51 C600 57.25 33.98 14.10 4.60 1.66 52.57 56.95 15.42 2.24 ND 17.34 20.96 0.51 C700 52.93 33.58 14.54 4.10 1.41 55.54 52.59 15.34 2.48 ND 17.95 20.45 0.53 Z-C600 72.89 17.76 7.23 2.89 1.59 59.41 27.73 16.11 28.42 16.40 11.06 11.53 0.62 d, dry base; ND, not detected; P(X), contents of components (Table 1); R(S), the relative content of S in char, R(S)=0.4×P(SO3)×P(Ash)+P(S), 0.4 is the proportion of S in SO3 molecular weight; R(Fe), the relative content of Fe in char, R(Fe)=0.7×P(Fe2O3)×P(Ash), 0.7 is the proportion of Fe in the molecular weight of Fe2O3; S/C=[R(S)]/P(C) 表 2 不同热解焦孔隙结构
Table 2 Pore structure of different pyrolysis char
Sample SBET/
(m2·g−1)Pore volume/
(10−2 cm3·g−1)Average pore
width/nmC000 3.95 2.40 24.33 C400 12.57 4.62 14.69 C500 18.49 5.26 11.38 C600 28.16 6.55 9.29 C700 17.60 5.43 12.33 Z-C400 1.47 0.87 23.40 Z-C600 7.98 3.34 16.73 SBET: specific surface area 表 3 样品热解前后不同结合态S、Fe相对含量
Table 3 Relative contents of different combined-form S and Fe before and after pyrolysis
Combined-form Before pyrolysis/% After pyrolysis/% Sulfides 55.28 30.01 Organic sulfur 35.88 59.59 Sulfates 8.84 10.40 Fe(Ш) 46.51 36.78 Fe(Ⅱ) 53.49 63.21 -
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