Possible Utilization of Silica Gel Sludge for the Removal of Phenol from Aqueous Solutions: Laboratory Studies

This paper discusses the adsorption capacity of silica gel sludge for phenol removal from aqueous solution. Kinetic experiments showed that phenol adsorption was completed after 2 h. Adsorption isotherms were measured for phenol from aqueous solution onto silica gel sludge under various pHs and temperatures. Results showed that the adsorption capacities for phenol was increased as pH decreased from 6.5 to 2. Temperature also was found to affect the adsorption isotherm. As temperature increases from 30 to 50°C, the adsorption capacity increases. The adsorption equilibrium of phenol on silica gel sludge was described by the linear Freundlich and Langmuir models. Furthermore, results showed that the isotherm parameters fit both linearized Langmuir and Freundlich adsorption isotherms. The Freundlich and Langmuir parameters at optimum pH was found as K _f=2.89, 1/n=0.23 and K _d=22.0, q _m=7.98, respectively. Whereas, for those at optimum temperature it was observed as K _f=2.87, 1/n=0.16 and K _d=20.93, q _m=7.91, respectively.     

Adsorption of mercury on laterite from Guizhou Province, China

The adsorption behaviors of Hg(Ⅱ) on laterite from Guizhou Province,China,were studied and the adsorption mechanism was discussed.The results showed that different mineral compositons in the laterite will cause differences in the adsorption capacity of laterite to Hg(Ⅱ).Illite and non-crystalloids are the main contributors to enhancing the adsorption capacity of laterite to Hg(Ⅱ).The pH of the solution is an important factor affecting the adsorption of Hg(Ⅱ) on laterite.The alkalescent environment (pH 7-9) ...     

污泥生物炭制备吸附陶粒

以城市污泥热解产生的生物炭(BC)与高岭土(KL)为原料制备吸附陶粒(SKC),研究其对环丙沙星(CIP)的吸脱附性能,开展吸附动力学和等温吸附特性研究,结合形貌、孔结构、物相组成、表面电位探讨其吸附机制,利用TCLP法研究重金属浸出特征.结果表明BC与KL以6∶4的质量比混合造粒,经1 050℃烧结5 min得到的SKC对CIP有明显的吸附效果,去除率达65.34%;SKC对CIP的吸附符合二级动力学模型,在不同质量浓度下的吸附特性适用于Freundlich等温吸附模型,吸附过程同时存在物理和化学吸附.SKC具有良好的孔隙结构,物相组成以硅铝氧化物、铁氧化物和金属磷酸盐为主,既能降低重金属的浸出毒性又具有良好的CIP吸附去除效果,有望为处理废水中高浓度CIP提供一种低成本可回收的吸附材料,也为BC的规模化安全利用提供了新思路.     

邻苯二甲酸酯在黄河沉积物上的吸附特性

文章利用反相高效液相色谱技术研究了黄河兰州段沉积物对水中邻苯二甲酸二甲酯(DMP)的吸附动力学,以及DMP、邻苯二甲酸二乙酯(DEP)、邻苯二甲酸正二丙酯(DnPrP)和邻苯二甲酸二丁酯(DBP)在沉积物上共存的等温吸附行为,探讨了助溶剂甲醇、离子强度等对吸附的影响。结果表明,在一定的浓度范围内,DMP在沉积物上的吸附速率先快后慢;DMP、DEP在沉积物上的等温吸附行为符合线性方程,而DnPrP、DBP的吸附等温线以Freundlich方程拟合最佳;沉积物对DMP的吸附容量还随着离子强度和溶液中甲醇百分比含量的增大而降低。     

交联壳聚糖对铀的吸附研究

以壳聚糖(CTS)为原料,在碱性条件下用环氧氯丙烷对壳聚糖进行化学改性,制得不溶水的交联壳聚糖(CCTS)。利用CCTS吸附铀(UO22+),探讨吸附动力学规律以及初始浓度,pH值的影响。实验结果表明,CCTS对UO22+的吸附符合Langmu ir吸附等温模型,并能用准二级速率方程对吸附动力学加以描述。当在CCTS为10 mg,pH为3,UO22+初始浓度为50μg/mL条件下,CCTS对UO22+的吸附去除率为98%以上。     

电炉钢渣对水中Cu2+、Cd2+和Pb2+的去除作用

以宝钢电炉钢渣为研究对象,考察了钢渣对溶液中重金属离子Cu2+、Cd2+、Pb2+的吸附动力学、吸附等温线、吸附热力学特征,借助多种分析手段(XRD、BET比表面分析、SEM/EDS等)对钢渣进行了理化性能测试和表征.结果表明,电炉钢渣对重金属离子的吸附速率较快,吸附速率顺序为Cd2+>Pb2+>Cu2+,吸附过程符合一级动力学模型(R2>0.99).吸附等温实验结果表明,Langmuir模型较为适合重金属离子在钢渣上的吸附,实验条件下对Cu2+、Cd2+、Pb2+离子的最大吸附容量分别为0.101、0.058、0.120 mmol.g-1.3种重金属离子在钢渣上的吸附是一个吸热(ΔH0<0)、熵值增大(ΔS0>0)的自发反应过程(ΔG0<0),熵效应是吸附反应自发进行的主要驱动力.SEM/EDS分析结果揭示了吸附前后钢渣表面形貌和化学成分的变化.电炉钢渣以其低价、高效性在重金属废水处理中具有广阔的应用前景.     

芳香族化合物在XAD-4上吸附机理的研究

通过批量吸附实验考查了7种芳香族化合物在XAD-4上的吸附热力学行为.结果表明,在实验条件下,Freundlich方程能很好地拟合这7种化合物在XAD-4上的等温吸附数据,且都为优惠吸附,吸附能力均随着温度的升高而降低.结合7种化合物的分子结构描述符和Freundlich方程的吸附平衡常数,建立了QSPR模型,较高的可决系数R2(0.991)、去一法交互检验可决系数R2CV(0.985)和外部预测集交互检验系数Q2ext(0.994)表明,该模型具有较高的稳定性能和预测能力.模型结果表明,水杨酸等7种芳香族化合物在XAD-4上的Freundlich吸附平衡常数与溶质疏水性能呈正比关系,与温度、溶质分子极性和溶质分子的氢键酸度常数呈反比关系.     

纳米塑料聚苯乙烯对水中铅离子的吸附行为研究

纳米塑料作为一种新兴污染物在水中可长久稳定存在,其表面吸附的重金属对水环境产生了潜在危害.本文研究了纳米塑料聚苯乙烯微球在吸附时间、溶液pH、氯化钠溶液、锰离子、温度等不同实验条件下对铅离子的吸附行为.结果表明,粒径为400 nm的单分散聚苯乙烯微球可快速吸附铅离子,吸附平衡时间约为30 min,吸附率达到53.30%.聚苯乙烯微球对铅离子的吸附动力学符合伪一级动力学,吸附等温线遵循Freundlich模型,吸附过程主要为非线性吸附.随着溶液pH的增加,铅离子平衡吸附量增加,静电作用是影响铅离子在聚苯乙烯微球上吸附的关键因素.增加溶液盐浓度,微塑料发生聚集,比表面积减小,吸附位点减少,铅离子的吸附量显著降低,在3.5%氯化钠溶液中,纳米塑料对铅离子的吸附率仅为7.5%.与重金属锰离子共存,可促进聚苯乙烯微球对铅离子的吸附.升高温度,纳米塑料对铅离子的平衡吸附量增加.     

Removal of perfluorinated surfactants from wastewater by adsorption and ion exchange——Influence of material properties,sorption mechanism and modeling

Perfluorooctane sulfonate(PFOS) has attracted increasing concern in recent years due to its world-wide distribution, persistence, bioaccumulation and potential toxicity. The influence of sorbent properties on the adsorptive elimination of PFOS from wastewater by activated carbons, polymer adsorbents and anion exchange resins was investigated with regard to their isotherms and kinetics. The batch and column tests were combined with physicochemical characterization methods, e.g., N_2 physisorption, mercury porosimetry, infrared spectroscopy, differential scanning calorimetry, titrations, as well as modeling. Sorption kinetics was successfully modelled applying the linear driving force(LDF) approach for surface diffusion after introducing a load dependency of the mass transfer coefficient βs.The big difference in the initial mass transfer coefficient βs,0, when non-functionalized adsorbents and ion-exchange resins are compared, suggests that the presence of functional groups impedes the intraparticle mass transport. The more functional groups a resin possesses and the longer the alkyl moieties are the bigger is the decrease in sorption rate.But the selectivity for PFOS sorption is increasing when the character of the functional groups becomes more hydrophobic. Accordingly, ion exchange and hydrophobic interaction were found to be involved in the sorption processes on resins, while PFOS is only physisorptively bound to activated carbons and polymer adsorbents. In agreement with the different adsorption mechanisms, resins possess higher total sorption capacities than adsorbents. Hence, the latter ones are rendered more effective in PFOS elimination at concentrations in the low μg/L range, due to a less pronounced convex curvature of the sorption isotherm in this concentration range.     

Removal of Cd2+ from water by Friedel’s salt (FS: 3CaO.Al2O3·CaCl2·10H2O): Sorption characteristics and mechanisms

The development of low-cost and efficient new mineral adsorbents has been a hot topic in recent years. In this study, Friedel’s salt (FS:3CaO·A12O3 ·CaCl2 ·10H2O), a hexagonal layered inorganic absorbent, was synthesized to remove Cd2+ from water. The adsorption process was simulated by Langmuir and Freundlich models. The adsorption mechanism was further analyzed with TEM, XRD, FT-IR analysis and monitoring of metal cations released and solution pH variation. The results indicated the adsorbent FS had an outstanding ability for Cd(Ⅱ) adsorption. The maximum adsorption capacity of the FS for Cd(Ⅱ) removal can reach up to 671.14 mg/g. The nearly equal numbers of Cd2+ adsorbed and Ca2+ released demonstrated that ion-exchange (both surface and inner) of the FS for Cd(Ⅱ) played an important role during the adsorption process. Furthermore, the surface of the FS after adsorption was microscopically disintegrated while the inner lamellar structure was almost unchanged. The behavior of Cd(Ⅱ) adsorption by FS was significantly affected by surface reactions. The mechanisms of Cd2+ adsorption by the FS mainly included surface complexation and surface precipitation. In the present study, the adsorption process was fitted better by the Langmuir isotherm model (R2 = 0.9999) than the Freundlich isotherm model (R2 = 0.8122). Finally, due to the high capacity for ion-exchange on the FS surface, FS is a promising layered inorganic adsorbent for the removal of Cd(Ⅱ) from water.