水土比、pH和有机质对沉积物吸附四环素的复合影响

Combination effects of pH, solution/soil ratio and inherent organic matter on the adsorption of tetracycline by sediments

为更深入了解抗生素在水环境迁移过程中受沉积物吸附影响的特征和规律,选取典型抗生素之四环素(TC)为代表,研究了不同水土比、pH及有机质对九龙江沉积物吸附TC的复合影响。通过在不同水土比条件下进行改变pH的吸附实验考察水土比和pH的复合影响,又以去除有机质前后的沉积物为吸附剂,在不同水土比、pH条件下对初始浓度范围为20~100 mg·L^(-1)的TC溶液进行等温平衡吸附试验,研究有机质在不同环境条件下对沉积物吸附TC的影响。结果显示pH的影响规律为:沉积物对TC的吸附率总是在酸性条件(pH=3~5)下出现最大值,并且吸附率总体上会随着pH的升高而降低。水土比的影响规律为:水土比的变化会使达到最大吸附率的pH位点和最大吸附率值都发生改变,如:水土比为0.125和0.25时,吸附率在pH=3时达到最大,分别是96.8%和95.3%;水土比0.5时,达到最大吸附率的pH值为5,且最大吸附率值降低至82.82%。这可能是吸附方式由阳离子交换转变为离子交换和配位络合的综合作用导致的。沉积物中有机质的影响研究发现,有机质不是单一的促进或抑制作用,而是在TC形态和沉积物的主要吸附方式发生变化的时候,其促进和抑制作用发生转换。

To understand the characteristic and mechanism of antibiotics migration in the aquatic environment influenced by sediment adsorption more clearly, this present study investigated the combination effects of pH, solution/soil ratio and inherent organic matter on the adsorption of tetracycline（TC）by sediments taken from Jiulong River. Composite effects of solution/soil ratio and pH on the adsorption was investigated by batch sorption experiments with different solution/soil ratio and pH value. The effects of inherent organic matter on the adsorp-tion at different solution/soil ratio and pH conditions were also reseached by batch sorption experiments with initial concentration of TC in the range of 20-100 mg·L^-1. The results showed that the sorption of TC by sendiment was strongly pH-dependent, of which the adsorption efficiency reached the maximum value at the pH rang of 3-5. Moreover, the adsorption efficiency decreased with pH increasing. The variety of solution/soil ratios changed the optimum pH value at which the maximum adsorption efficiency reached, i.e. The maximum adsorption efficiencies were all reached at the optimum pH 3 when solution/soil ratio was 0.25 and 0.125 with the maximum value 95.3% and 96.8%,respectively. While the optimum pH value was changed to pH 5 when solution/soil ratio was 0.5（The maximum adsorption efficiency was decreased to 82.82%）. The reason may be that the main way of adsorption was changed from cation exchange to combination of ion exchange and complexation. Furthermore, the effect of the inherent organic matter of the sendiment could promote or inhibit the sorption of TC depending on the different pH, TC fractions, equilibrium concentrations and other conditions.