pH和共存阳离子对草莓茎吸附水体氨氮的影响

为了开发新型氨氮吸附剂和探讨环境因素对氨氮吸附的影响,以草莓茎为吸附材料,通过批平衡法研究了不同初始pH、共存阳离子、初始浓度和温度下氨氮去除的特点.结果表明,等温吸附符合Langmuir和Freundlich这2种模型,理论最大吸附量qm在15、25和35℃下分别为3.05、4.24和4.79 mg.g-1.温度升高有利于草莓茎对氨氮的吸附.草莓茎吸附氨氮最适初始pH为4～8.低pH减少草莓茎表面负电荷,高pH减少溶液中NH 4+的含量,都减少氨氮的吸附.草莓茎对溶液pH的缓冲则缓和了两者对氨氮吸附的影响.共存阳离子K+、Na+、Ca2+、Mg2+对草莓吸附铵离子没有竞争作用,而Zn2+、Al3+则由于其水解降低溶液的pH而显著降低草莓茎对氨氮的吸附.草莓茎吸附氨氮的应用pH范围较广且不易受废水中常见金属阳离子的干扰,说明草莓茎不仅可以作为废水中氨氮的吸附剂原料,而且较大多数矿物原料还有其自身的优势.

Effects of pH and Coexisting Cations on Ammonia Adsorption from Aqueous Solution by Strawberry Stem Powder

Batch equilibrium experiments were carried out to study ammonia adsorptions from aqueous solution by strawberry (Fragaia ananassaDuchesne) stem powder. The effects of pH, coexisting cations, initial ammonia concentration and temperature were investigated as well. The results showed that the equilibrium data fitted well to the Langmuir model and Freundlich model, and the maximum adsorption capacities were 3.05, 4.24 and 4.79 mg·g^-1 at 15, 25 and 35°C respectively. The increase of temperature was favorable to ammonia adsorption. The optimal pH of ammonia adsorption was in the range of 4-8. The NH⁺₄ content decreased at higher pH and the negative charges decreased at lower pH, resulting in the decrease of ammonia adsorption at both higher and lower pH. The pH changes after adsorption buffered both effects. K⁺, Na⁺, Ca²⁺ and Mg²⁺ had no effect on ammonia adsorption by strawberry stem, but Zn²⁺ and Al³⁺ decreased the adsorption for their hydrolyzation. The ammonia adsorption by strawberry stem powder could be applied in a large pH range and could not be affected by usual metal cations in wastewater, therefore the strawberry stem powder not only could be a suitable ammonia adsorbent, but also had advantages comparing with most mineral materials.