谷壳的差热红外扫描电镜分析及对铜铅离子的生物吸附研究

Characterization of chaff and biosorption of copper and lead ions from aqueous solution

用差热分析(DTGDTA)、红外光谱(FTIR)、扫描电镜(SEM/EDS)等方法对谷壳的质量随温度上升而变化的情况、表面的官能团、表面形态及主要元素构成等进行了分析,并研究了谷壳对水溶液中Cu2+、Pb2+的生物吸附作用.加热170℃时谷壳质量损失约6%,至170～290℃时质量损失约45%,至500℃时质量仅余约11%.在320℃、440℃分别有2个放热峰.谷壳的红外吸收光谱图主要由碳水化合物如木质素、纤维素等的吸收带组成.红外光谱分析表明,1735cm-1和1615cm-1处的吸收峰为不同CO的伸缩振动峰;1515cm-1处为苯环的骨架振动峰,而1243cm-1处是苯羟基中C—O的伸缩振动峰.1456cm-1处的吸收峰为CH3—和CH2—的弯曲振动峰,1374cm-1处是甲基的弯曲振动峰.SEM/EDS分析表明,谷壳表面粗糙,且主要由碳氧硅铝元素构成.结果表明,吸附时间、溶液pH、吸附剂用量、金属离子初始浓度及Na+和Ca2+离子对吸附均有影响.谷壳对Cu2+、Pb2+的吸附在30min基本达到平衡,在pH为5左右吸附效果较好,Ca2+对吸附的影响比Na+严重.随初始浓度的增加,吸附量增大,且吸附可用Langmuir方程描述.在本实验条件下,谷壳对Cu2+、Pb2+的最大吸附量分别为3.46mg·L-1、12.5mg·L-1.一种金属离子的存在能显著降低谷壳对另一种金属离子的吸附,且Pb2+对Cu2+的影响较Cu2+对Pb2+的影响更严重.单一体系和混合体系的实验结果表明,谷壳对单一体系中Cu2+、Pb2+的吸附能力分别大于对混合溶液中Cu2+、Pb2+的吸附能力.

The characteristics of cereal chaff obtained from agricultural by - product are studied by thermogravimetry analysis（TGA） , differential thermal analysis（DTA） , Fourier-Transform Infrared Analysis spectroscopy（FTIR） and Scanning Electron Microscopy/ An energy dispersive X-ray Spectra（ SEM/ EDS） , while the adsorption ability of cereal chaff was investigated for the removal of Cu（Ⅱ） and Pb（Ⅱ） from single （non-competitive） and binary （ competitive） aqueous systems, Heated up to 170℃, a mass loss of 6% is observed, From 170 -290℃ , a mass loss of 45% is observed, Up to 500℃, the mass of remains is only 11%. The max peaks at 320℃ and 440℃ in DTA are observed by exothermic decomposed reaction, respectively. The IR spectroscopy of the chaff is mainly composed of the adsorption of carbohydrates, lignin, cellulose etc. The peaks located at 1734 and 1651 cm^-1 are characteristics of carbonyl groups stretching from carboxylates and ketones. The peak near 1515 cm^-1 is assigned to the stretching in aromatic rings. The peak near 1456 cm^-1 is attributed to the bending stretching of CH2- and CH3-. The peak at 1243 cm^-1 is from C-O stretching vibration in phenols. SEM/EDS analysis shows that the main elements of chaff are carbon, oxygen, silicon, aluminum and the surface of chaff is roughness. Adsorption of the objective heavy metal ions by chaff strongly depends on pH, contact time, initial concentration of the heavy metal ions and adsorbent dosage. The experimental data for single Cu （Ⅱ） and Cd （Ⅱ） systems fitted the Langmuir isotherm model excellently. The maximum adsorption capacities of Cu （Ⅱ） and Pb （Ⅱ） per gram chaff were calculated as 3.46 and 12.5 mg·L^-1 for single system, respectively. For binary system, the adsorptive capacity for one metal ion was affected by another metal ion, but the effect of Cu（Ⅱ） by Pb（Ⅱ） is significantly, The affinity of chaff for Pb（Ⅱ） is greater than Cu（Ⅱ）. The results show that chaff may be used effectively in removal of Cu（Ⅱ） and Pb（Ⅱ） ions from aqueous systems for environmental cleaning purposes.