Kinetic and Thermodynamic Studies for the Removal of Nickel Ions from an Aqueous Solution by Adsorption Technique

The kinetics and dynamics of nickel ions adsorption on activated carbon and bentonite were studied. The influence of parameters (pH, amount of adsorbent, adsorbate concentration, solution volume, rotation speed, and temperature) were investigated. Kinetic models of pseudo-first, pseudo-second and Weber-Morris models were applied. The data was better reported by the pseudo-second order model. Freundlich, Langmuir, and D-R models were utilized for the analysis of adsorption equilibrium. Evaluation of thermodynamic parameters reveal that adsorption is spontaneous and endothermic in nature. From the experimental data, it was concluded that bentonite has more efficiency for the adsorption of nickel ions than activated carbon.     

有机膨润土改性高吸油树脂复合材料的合成及性质

以十六烷基三甲基溴化铵为表面改性剂制备了有机膨润土,并制备了以甲基丙烯酸十六酯为单体的吸油树脂/有机膨润土复合材料.采用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)、扫描电子显微镜(SEM)对样品进行分析.结果表明,经十六烷基三甲基溴化铵改性的膨润土层间距由原来的1.12 nm增大到1.87 nm;所得有机膨润土/吸油树脂复合材料对四氯化碳的饱和吸油率为16.3 g/g.     

Evaluation of the Thermodynamic Parameters for the Adsorption of Some Hydrocarbons on Chemically Treated-Bentonites by Inverse Gas Chromatography

Inverse gas chromatography has been used to evaluate the adsorption parameters (ΔH_a, ΔH_st, ΔS_a and ΔG_a) of some probe molecules, each representing a class of organic (n-hexane, cyclohexane, benzene, n-octane, 1-octene and isooctane) on bentonite and chemically treated-bentonites. The adsorption parameters of the probes on the bentonite samples were determined in infinite dilution region. Adsorption of the organic species was investigated in the temperature range of 200–275^∘C, using a flame ionization detector, and nitrogen as a carrier gas. The net retention volumes (V_n) of the probes were determined by the help of the retention times (t_R) observed on gas chromatograms for each probe. Injection was made at least three times for each probe, obtaining reproducible results of ± 0.5%. It was found that benzene exhibits more negative ΔH than for n-hexane and cyclohexane on all of the adsorbents. In addition, it was found that 1-octene exhibits more negative ΔH than for n-octane and isooctane on the chemically treated-bentonites, whereas n-octane exhibits more negative ΔH than for 1-octene and isooctane on the natural bentonite. Also, interactions of benzene with the natural- and chemically treated-bentonites were found to be stronger than those of n-hexane and cyclohexane with the same carbon number. Again, interactions of the 1-octene with the chemically treated-bentonites were found to be stronger those of n-octane and isooctane with the same carbon number. On the contrary, interactions of n-octane with the untreated-bentonite were found to be stronger than those of 1-octene and isooctane.     

改性脚润土处理染色废水的研究

将自制的改性膨润土作为吸附混凝剂，处理不同的染色废水，COD去除率和脱色率分别可达90%和9500，且鹰水pH在4-9范围内时，脱色率较稳定.通过改性膨润土与膨润土废水处理效果的比较，初步表明改性膨润土可提高染色废水处理效率.     

Desorption of Heavy Metals from Typical Soil Components (Clay,Peat) with Glycine

Abstract

Natural organic chelating agents take part in the mobilization and translocation of heavy metals in unpolluted and polluted soils. They also have to be considered as possible extracting agents for the decontamination of heavy metal polluted soils. For an assessment of the desorption capability of glycinc, heavy metals (Cd, Cu, Ni, Pb, Zn) were adsorbed onto typical soil components (bentonite and peat). The metal loaded sorbents were resuspended in aqueous solutions of glycine at pH 7.0 and 4.5 and the quantities of the desorbed metals were analysed in the liquid phase. Furthermore, the dependency of the desorption rate on the duration of experiments and the metal content were investigated. The remobilization of heavy metals from bentonite by glycine at pH 7.0 decreases following the order Cu > Ni > Zn > Cd > Pb and ranges from 95% to 9.5%. The desorption rate was significantly lower at pH 4.5 and in suspensions of peat.     

膨润土-壳聚糖及其改性吸附剂脱除燃烧烟气中Hg0的性能研究

应用VM3000在线测汞仪作为检测手段,在固定床实验台架上,以改性膨润土 壳聚糖为吸附剂进行脱汞(Hg⁰)实验研究。采用N₂吸附/脱附、扫描电镜(SEM)和傅里叶变换红外光谱(FT-IR)等分析仪对吸附剂进行表征。分析发现改性后吸附剂的孔隙和比表面积降低;碘离子进入了膨润土的内部,碘、硫酸和壳聚糖中的氨基发生了化学反应。脱汞实验表明,负载壳聚糖的膨润土吸附剂表现出较膨润土差的脱汞效果,证明膨润土负载壳聚糖脱除气态中单质汞的机理和液相中二价汞的机理不同。经碘改性后,各吸附剂均可不同程度地提高其脱汞效率,且以碘改性膨润土的脱汞效果最好;碘改性吸附剂中添加适量的硫酸后,膨润土负载壳聚糖吸附剂的脱汞效率从85%提高至100%,因与膨润土负载壳聚糖不同的物理化学特性,碘和硫酸改性的膨润土的脱汞效率则降低。     

Biodegradable polymer/clay systems for highly controlled release of NPK fertilizer

The aim of this work was to obtain biodegradable polymeric systems based on poly(hydroxybutyrate) (PHB) for use in the controlled release of agrochemicals and to analyze the relationship between the properties of polymers and the rates of release of active compounds. Two types of systems were obtained: one using nitrogen, phosphorous, and potassium (NPK) fertilizer directly mixed within the polymer matrix and another with the fertilizer previously incorporated in bentonite (Bent) and mixed with the polymer. The systems were obtained by melt processing and then evaluated by their properties. The release of the active compounds was analyzed by conductometric analysis using an aqueous solution as release medium for 240 hours. The obtained results were correlated with the biodegradation process of PHB. All of the systems presented a significant reduction in the active compounds released to the environment as compared with the direct application of NPK. The PHB/NPK systems showed a release of up to 37% of the compounds, while the PHB/m‐Bent showed greater control, with a release between 4% and 11% after 240 hours. In addition, the properties of the polymer systems presented a direct relationship with the rate of active compounds released. The type of production process, properties, and biodegradability indicate interesting potential of these systems for application in the controlled release of active compounds.     

活性白土的制备

活性白土的制备谭钦德，陈淑荷，谭志诚（佛山大学化学系佛山５２８０００）关键词膨润土，活性白土，活化工艺活化是膨润土深加工中的一个基本工艺过程。活性白土既可直接用作医药、化妆品和涂料等的原料，也可用于油品制造的脱色以及碱性、极性基团的吸附工艺［１～３］...     

Adsorption of 2,2′-bipyridyl onto sepiolite,attapulgite and smectite group clay minerals from anatolia: The FT-IR and FT-Raman spectra of surface and intercalated species

The adsorption of 2,2-bipyridyl by natural sepiolite, attapulgite, hectorite, saponite and natural and ion exchanged (Mn, Fe, Co, Ni, Cu, Zn or Sn) bentonites has been investigated by FT-IR and FT-Raman spectroscopy. Spectroscopic results indicate that most of the adsorbed molecules are coordinated to either exchangeable cations (in the case of smectite group clays) or Lewis acidic centres (in the case of sepiolite and attapulgite) as bidentate ligands. The formation of monoanionic surface species has also been detected, to a relatively small extent. No physisorbed surface species has been observed. XRD patterns and UV-visible spectra of the samples are also recorded for additional information.Author for correspondence.     

Stabilization of emulsions by heterocoagulation of clay minerals and layered double hydroxides

 Paraffin/water emulsions were stabilized by colloidal particles without surface active agents. Mixtures of two types of particles with opposite signs of charge were used: a layered double hydroxide (the hydroxide layers carry positive charges) and the clay mineral montmorillonite (the silicate layers carry negative charges). The emulsions were very stable and did not separate a coherent oil phase. The stability of the emulsion (no oil coalescence after centrifugation) was independent of the mixing ratio of both the compounds when the total solid content was >0.5%. Solid contents up to 2.0% were optimal. In contrast to stability, flow behavior of the emulsion was dependent on the mass fraction χ of the hydroxide. The maxima of viscosity and yield value were observed at χ≈0.2–0.3; the emulsion showed pronounced antithixotropic behavior. Weak thixotropic properties, smaller viscosities and yield values were observed at χ≤0.2 and ≥0.5. In the absence of the clay mineral, the double hydroxide particles stabilize by forming envelopes around the oil droplets. Addition of bentonites creates a three-dimensional network of particles with high elasticity which impedes coalescence of the oil droplets. Received: 9 March 1998 Accepted: 6 April 1998