Melegari Silvia P, Matias William G
Laboratory of Environmental Toxicology (LABTOX), Department of Sanitary and Environmental Engineering, University Campus "Trindade", Florianopolis, SC, CEP 88040-970, Brazil.
Chem Cent J. 2012 Aug 14;6(1):86. doi: 10.1186/1752-153X-6-86.
This study evaluated the adsorption capacity of the natural materials chitin and oyster shell powder (OSP) in the removal of saxitoxin (STX) from water. Simplified reactors of adsorption were prepared containing 200 mg of adsorbents and known concentrations of STX in solutions with pH 5.0 or 7.0, and these solutions were incubated at 25°C with an orbital shaker at 200 RPM. The adsorption isotherms were evaluated within 48 hours, with the results indicating a decrease in STX concentrations in different solutions (2-16 μg/L). The kinetics of adsorption was evaluated at different contact times (0-4320 min) with a decrease in STX concentrations (initial concentration of 10 μg/L). The sampling fractions were filtered through a membrane (0.20 μm) and analyzed with high performance liquid chromatography to quantify the STX concentration remaining in solution.
Chitin and OSP were found to be efficient adsorbents with a high capacity to remove STX from aqueous solutions within the concentration limits evaluated (> 50% over 18 h). The rate of STX removal for both adsorbents decreased with contact time, which was likely due to the saturation of the adsorbing sites and suggested that the adsorption occurred through ion exchange mechanisms. Our results also indicated that the adsorption equilibrium was influenced by pH and was not favored under acidic conditions.
The results of this study demonstrate the possibility of using these two materials in the treatment of drinking water contaminated with STX. The characteristics of chitin and OSP were consistent with the classical adsorption models of linear and Freundlich isotherms. Kinetic and thermodynamic evaluations revealed that the adsorption process was spontaneous (ΔGads < 0) and favorable and followed pseudo-second-order kinetics.
本研究评估了天然材料几丁质和牡蛎壳粉（OSP）从水中去除麻痹性贝类毒素（STX）的吸附能力。制备了简化的吸附反应器，其中含有200毫克吸附剂和已知浓度的STX，溶液pH值为5.0或7.0，这些溶液在25°C下以200转/分钟的速度在轨道摇床上孵育。在48小时内评估吸附等温线，结果表明不同溶液（2 - 16μg/L）中STX浓度降低。在不同接触时间（0 - 4320分钟）下评估吸附动力学，STX浓度降低（初始浓度为10μg/L）。取样部分通过0.20μm的膜过滤，并用高效液相色谱分析以量化溶液中剩余的STX浓度。
发现几丁质和OSP是有效的吸附剂，在评估的浓度范围内（18小时内超过50%）具有从水溶液中去除STX的高能力。两种吸附剂对STX的去除率均随接触时间降低，这可能是由于吸附位点饱和，表明吸附是通过离子交换机制发生的。我们的结果还表明，吸附平衡受pH影响，在酸性条件下不利。
本研究结果证明了使用这两种材料处理受STX污染的饮用水的可能性。几丁质和OSP的特性与线性和弗罗因德利希等温线的经典吸附模型一致。动力学和热力学评估表明，吸附过程是自发的（ΔGads < 0）且有利，并遵循准二级动力学。
