三种不同生物质炭对2,4-二氯苯氧乙酸吸附特性的研究

以植物类生物质原料(玉米秸秆和毛杨树叶)、城市污泥两类原材料在400℃条件下制备生物质炭(秸秆、毛杨树叶以及城市污泥三种生物质炭分别表示为J400、Y400和W400),使用酸洗法去除生物质炭表面灰分优化生物质炭,采用批量吸附实验的方法分析三种生物质炭对2,4-二氯苯氧乙酸(简称2,4-D)的吸附特性,并结合元素分析及显微红外等分析方法,探讨生物质原料对生物质炭吸附2,4-D吸附特性的影响。结果表明:三种生物质炭的元素含量、O/C、H/C和(H+O)/C存在差异,大小顺序均为W400Y400J400,表明秸秆生物质炭具有更强的疏水性和更低的极性,有利于提高生物质炭对有机物的吸附能力。吸附试验显示秸秆生物质炭、杨树生物质炭、污泥生物质炭对2,4-D的吸附特性及吸附能力不同,吸附量大小依次为2.732、2.650、2.633 mg·g(-2)。三种生物质炭的红外光谱结果相似,但在O-H、饱和C-H和不饱和C-H面外振动等处存在差异;污泥生物质炭在吸附2,4-D后多处位点的吸收峰发生变化,而杨树和秸秆生物质炭发生变化的位点较少;污泥生物质炭与其他两种生物质炭对2,4-D的吸附机制差异较大。

Adsorption of 2, 4-Dichlorophenoxyacetic acid in aqueous solution by biochars derived fromthree feedstocks

In this study, we investigated the adsorption kinetics and isotherms of a model solute(2,4-dichlorophenoxyacetic, or 2,4-D)by biochars prepared from three feedstocks(corn stover, poplar leaves and sewage sludge)at 400℃. At the same pyrolysis temperature, sewage sludge biochar had significant low C content in comparison with those derived from plant materials, but their O/C, H/C and (H+O)/C radio had similar trends. The properties of feedstocks greatly influenced the adsorption characteristics of biochars. The mechanisms of 2,4-D ad-sorption by sewage sludge biochar were obviously different from those of the other two biochars. The selection of adsorbents must be case-by-case based on the characteristics of biochar feedstocks. This study provides us a potential way to use relatively more suitable biochar in reducing the leaching of organochlorine pesticides.