Speciation of the ionizable antibiotic sulfamethazine on black carbon (biochar).
Speciation of the ionizable antibiotic sulfamethazine on black carbon (biochar).
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DOI：
10.1021/es202487h
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发表时间：
2011-10
影响因子：
11.4
通讯作者：
M. Teixidó;J. Pignatello;J. Beltrán;M. Granados;J. Peccia
中科院分区：
文献类型：
--
作者：
M. Teixidó;J. Pignatello;J. Beltrán;M. Granados;J. Peccia
黑碳对可电离化合物的吸附特性很差。兽医抗生素磺胺二甲嘧啶（SMT; a.k.a.，磺胺二甲嘧啶; pK（a1）= 2.28，pK（a2）= 7.42）作为浓度、pH、无机离子、有机离子和分子的函数被测定。SMT表现出非常规的吸附行为。尽管其具有亲水性（log K（ow）= 0.27），但在pH 5（SMT（0）占优势）下的分配比K（d）高达10（6）L kg（-1），是文献报道的K（oc）的10（4）倍。K（d）在高pH和低pH下降低，但与电离形式的K（ow）的降低不相称。在pH 1下，其中SMT（+）占主导并且表面是正的，主要驱动力是质子化苯胺环与富π电子石墨烯表面的π-π电子供体-受体相互作用，称为π（+）-π EDA，而不是普通的静电阳离子交换。在碱性区域中，SMT（-）占优势并且表面是负的，吸附伴随着与水的近化学计量的质子交换，导致OH（-）的释放和SMT（0）与表面羧酸盐或酚盐之间异常强的氢键的形成，归类为负电荷辅助的氢键，（-）CAHB。在pH 5时，SMT（0）的吸附伴随着部分质子释放，并与三甲基苯基铵离子竞争，表明SMT（+）和/或两性离子SMT（±）的贡献，它们利用了π（+）-π EDA相互作用和库仑吸引力对去质子化表面基团的作用。实质上，在吸附状态下，相对于溶解状态，pK（a1）和pK（a2）均增加，SMT（±）稳定。
Adsorption of ionizable compounds by black carbon is poorly characterized. Adsorption of the veterinary antibiotic sulfamethazine (SMT; a.k.a., sulfadimidine; pK(a1) = 2.28, pK(a2) = 7.42) on a charcoal was determined as a function of concentration, pH, inorganic ions, and organic ions and molecules. SMT displayed unconventional adsorption behavior. Despite its hydrophilic nature (log K(ow) = 0.27), the distribution ratio K(d) at pH 5, where SMT(0) prevails, was as high as 10(6) L kg(-1), up to 10(4) times greater than literature reported K(oc). The K(d) decreases at high and low pH but not commensurate with the decline in K(ow) of the ionized forms. At pH 1, where SMT(+) is predominant and the surface is positive, a major driving force is π-π electron donor-acceptor interaction of the protonated aniline ring with the π-electron rich graphene surface, referred to as π(+)-π EDA, rather than ordinary electrostatic cation exchange. In the alkaline region, where SMT(-) prevails and the surface is negative, adsorption is accompanied by near-stoichiometric proton exchange with water, leading to the release of OH(-) and formation of an exceptionally strong H-bond between SMT(0) and a surface carboxylate or phenolate, classified as a negative charge-assisted H-bond, (-)CAHB. At pH 5, SMT(0) adsorption is accompanied by partial proton release and is competitive with trimethylphenylammonium ion, signifying contributions from SMT(+) and/or the zwitterion, SMT(±), which take advantage of π(+)-π EDA interaction and Coulombic attraction to deprotonated surface groups. In essence, both pK(a1) and pK(a2) increase, and SMT(±) is stabilized, in the adsorbed relative to the dissolved state.