The removal of textile dyes by diatomite earth

The adsorption of some textile dyes by diatomite was investigated using Sif Blau BRF (SB), Everzol Brill Red 3BS (EBR), and Int Yellow 5GF (IY). Adsorption of these textile dyes onto diatomite earth samples was studied by batch adsorption techniques at 30 degrees C. The adsorption behavior of textile dyes on diatomite samples was investigated using a UV-vis spectrophotometric technique. The effect of particle size of diatomite, diatomite concentration, the effect of initial dye concentrations, and shaking time on adsorption was investigated. Adsorption coverage over the surface of diatomite was studied using two well-known isotherm models: Langmuir's and Freundlich's. These results suggest that the dye uptake process mediated by diatomite has a potential for large-scale treatment of textile mill discharges. According to the equilibrium studies, the selectivity sequence can be given as IY > SB > EBR. Values of the removal efficiency of the dyes ranged from 28.60 to 99.23%. These results show that natural diatomite holds great potential to remove textile dyes from wastewater.     

Effect of alkali metals,alkaline earth metals and lanthanides on the adsorption of uranium on activated charcoal from aqueous solutions

Effects of alkali metals, alkaline earth metals and some lanthanides on the adsorption of uranium on activated charcoal from aqueous solutions have been studied. These effects are correlated with the ionic radii of metal ions present in the solutions. Adsorption capacity, X_m and binding energy contant, K for uranium adsorption were calculated from the Langmuir equätion. The mean energy of adsorption, E_s was calculated from adsorption energy constant, K, values determined from the Dubinin-Radushkevich isotherm equation. Wavelength dispersive X-ray fluorescence spectrometry was used for measuring the uranium concentration.     

国产硅藻土吸附尿激酶机理的研究

在常温下, 尿激酶在浙江土和吉林土表面的吸附等温线分别为V型和II型; 焙烧后两者皆转为III型。吸附等温线类型与硅藻土表面结构、孔结构、表面ζ电位有关。在400℃焙烧的硅藻土等电点值最低, 吸附量最大; 改性后, 吸附量也发生改变。本文还测定了尿激酶在硅藻土表面的吸附形态, 其吸附等温线方程符合0/(1-0)=(Kc)^1/β, 并讨论了平衡常数K和尿激酶吸附功能链段数β随温度的变化。     

Adsorption of Anionic Dyes onto Chitosan-modified Diatomite

The purpose of this work is to study the possibility of anionic dyes Reactive Red M-8B(RR) and Direct Green B(DG) adsorbed on chitosan-modified diatomite. The characteristics of adsorbent, adsorption isotherms and the influence of adsorption time, temperature and pH were researched in this work. The results show that the mo- dified diatomite had a much better adsorption capability than the natural diatomite. The adsorption capacities of chitosan-modified diatomite for RR and DG were 94.46 and 137.0 mg/g, respectively. Both adsorption time and adsorption temperature provided a positive effect on the dye adsorption. Within the experimental pH range, the adsorbance was enhanced at lower pH but reduced sharply at high pH. On the basis of the experimental results and discussion, electrostatic attraction is considered as the main mechanism of this chemisorption.     

Functionalization of chitosan with 3,4-dihydroxybenzoic acid for the adsorption/collection of uranium in water samples and its determination by inductively coupled plasma-mass spectrometry

A chitosan resin derivatized with 3,4-dihydroxybenzoic acid moiety (CCTS-DHBA resin) was newly synthesized for the collection/concentration of trace uranium by using cross-linked chitosan (CCTS) as base material, and the adsorption behavior of uranium as well as 60 elements on the resin was examined by passing the sample solutions through a mini-column packed with the resin. After the elution of the collected elements on the resin with 1 M HNO₃, the eluates were measured by inductively coupled plasma-mass spectrometry (ICP-MS).The CCTS-DHBA resin can adsorb several metal cations and several oxoanionic elements at appropriate pH. Among these metal ions, uranium shows an excellent adsorption behavior on this resin. Uranium as UO₂²⁺ species can be adsorbed on the resin by chelating mechanism with adsorption capacity of 330 mg g⁻¹ resin. Through the column treatment, the complete removal of large amounts of alkali and alkaline earth matrices without any loss of adsorption efficiency over prolonged usage were achieved with this resin.The CCTS-DHBA resin was applied to the adsorption/collection of uranium in tap water, river water and seawater samples with satisfactory results. The validation of the proposed method was carried out by analyzing uranium in the standard reference materials of SLRS-4, CASS-4, and NASS-5 after passing through the CCTS-DHBA resin, and the results showed good agreement with the certified values.     

改性硅藻土对富营养化水体中磷的吸附行为

以硅藻土原土为原料,通过碱洗及浸渍负载羟基氧化铁对其进行改性,利用SEM、XRD及物理吸附仪对改性硅藻土的形貌、比表面积等进行表征,并研究了改性硅藻土对富营养化水体中磷的吸附性能。结果表明,(1)改性后,硅藻土杂质元素减少,孔径明显增大,比表面积增大23倍,并有效负载了β-FeO(OH);(2)其对磷的吸附受温度及pH值的影响,温度越高,达到吸附平衡时间越短,吸附容量也越大;在pH值为4~11之间,吸附容量随pH的增大而减小;(3)拟二级反应动力学方程,能准确地描述改性硅藻土对磷的吸附,而粒内扩散,不是改性硅藻土对磷吸附的唯一控制步骤;(4)改性硅藻土在富营养化水体中对磷的吸附行为,符合Freundlich等温线方程,其吸附过程为物理吸附,吸附过程焓变(H)为39.949kJ/mol,各温度下的自由能变(G)均小于零,熵变(S)均为正值,该吸附过程是自发的吸热物理过程。     

聚乙烯亚胺表面改性硅藻土及其对苯酚吸附特性的研究

使用紫外吸收光度法研究了硅藻土对聚乙烯亚胺(PEI)的等温吸附;采用浸渍法,用PEI对硅藻土进行了表面改性;使用4-氨基安替比林光度法研究了经PEI表面改性的硅藻土对苯酚的捕集行为.研究结果表明,凭借强烈的静电相互作用,表面带负电荷的硅藻土粉体对阳离子性大分子PEI具有很强的吸附能力,等温吸附满足Freundlich吸附方程;经PEI表面改性后,硅藻土粉体表面的电性发生了根本性改变,且等电点由pH=2.0移至pH=10.5;在中性溶液中,改性粉体通过氢键作用与静电相互作用的协同,对水溶液中的苯酚会产生很强的捕集作用,饱和吸附量可达92 mg/g;在酸性溶液中改性粉体通过氢键相互作用,对水溶液中的苯酚产生一定的吸附作用,但由于PEI分子链高度的质子化,氮原子对苯酚的氢键相互作用很弱,吸附量很低.     

Flocculation of diatomite by methylated egg albumin

A common and inexpensive protein, egg albumin, was applied to the solid-liquid separation or flocculation of diatomite. Egg albumin was methylated in a 0.05 M HCl methyl alcohol solution at room temperature. About 90% of the carboxylic groups of egg albumin could be methylated within 24 h. The adsorption of egg albumin onto diatomite at pH 6.8 was remarkably enhanced by methylation. The adsorption constant of methylated egg albumin to diatomite at 30 degrees C was about 100-fold larger than that of native egg albumin; however, the adsorption constant of methylated egg albumin decreased to about 1/100 with temperature decreasing from 30 to 6 degrees C. The saturated adsorption amount of egg albumin was also increased by the methylation. The flocculating ability of methylated egg albumin was examined with a diatomite suspension at 6 and 30 degrees C in the pH range from pH 2 to 11. The diatomite suspension was effectively flocculated by the addition of small amounts of methylated egg albumin (only 0.5-1 wt% against diatomite) over a wide pH range from pH 3 to 10.     

Fe–Mn binary oxide incorporated into diatomite as an adsorbent for arsenite removal: Preparation and evaluation

Fe–Mn binary oxide incorporated into diatomite (FMBO-diatomite) was prepared by a simple coating method, and exhibited high oxidation and adsorption ability for arsenite [As(III)]. After being incorporated by Fe–Mn binary oxide, the surface area of diatomite increased 36%, and the pore volume increased five times. The pH_zpc of FMBO-diatomite was determined to be 8.1. These characteristics are responsible for the increased As(III) adsorption efficiency. The adsorption equilibria of As(III) on FMBO-diatomite were described well by a Langmuir isotherm model due to the homogeneous distribution of Fe–Mn binary oxide on a diatomite surface. As(III) was oxidized into As(V), and then adsorbed by FMBO-diatomite. The oxidation and adsorption efficiencies for As(III) depended deeply on the pH of solution. When the pH was raised to 8.1, the As(III) adsorption efficiency of FMBO-diatomite was almost equal to the As(III) oxidation efficiency. Silicate and phosphate had negative effects on As(III) adsorption. Also the influence of silicate and phosphate with the pH variation was different.     

Adsorption of Malachite Green by Diatomite: Equilibrium Isotherms and Kinetic Studies

The utilization of diatomite as potential adsorbent to remove malachite green (MG) from aqueous solution was developed. The characterization of the diatomite was evaluated by scanning electron microscope (SEM) and Brurauer Emmerr Teller (BET). The operating variables of pH, diatomite mass, initial MG concentration, and adsorption reaction time were studied. The equilibrium, kinetics, and thermodynamic parameters were investigated as well. It was found that the diatomite was composed of integral and almost circle sieve tray with lots of small pores on it, which afforded the diatomite high specific surface area of 46.09 m² g^?1. The optimum pH and reaction time were 7 and 90 minutes, respectively. The MG removal increased accordingly as the diatomite mass increased. The isotherm results showed that the equilibrium data were fitted to Langmuir model better, indicating the MG adsorption was better characterized by mono-layer. The maximum mono-layer capacity obtained from Langmuir was 23.64 mg g^?1 at 25°C. The kinetic studies indicated that experiment data followed pseudo-second-order model better. It also revealed that intraparticle diffusion was not the only rate-controlling step. The thermodynamic results concluded that the adsorption process was endothermic and more favorable at high temperature. Researches confirmed the applicability of diatomite as an efficient adsorbent and low-cost process to remove hazardous materials.     

Enhanced Dye Adsorption by Microemulsion-Modified Calcined Diatomite (μE-CD)

This study attempted to improve the adsorption performance of calcined diatomite for the removal of colour from wastewaters through modification with microemulsions. The surface area, pH_ZPC, Fourier transform infrared (FTIR) of calcined diatomite and μE-CD were studied. It is found that an increase in the BET surface area, pH_ZPC and total pore volume after modification was obtained. A decrease in average pore volume was observed after modification. This suggests that the pore opening deceased to be in the micro- and meso-pore region hence the adsorption capacity for the modified adsorbent will be enhanced by reducing the escaping of dye molecules. The influence of concentration, pH and particle size on the adsorption capacities of methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was investigated. It was concluded from FTIR and pH analysis that the predominant mechanism of RY molecules onto μE-CD is by an electrostatic attraction between the carboxylate anion and the dye. In the case of MB and RB, the adsorption mechanism could be a combination of different mechanisms such as electrostatic attraction, capturing by microemulsion micelles in the pores of the calcined diatomite or the hydrophobic attraction. The adsorption capacities were higher than unmodified calcined diatomite. In the case of adsorption of MB molecules, a high adsorption capacity onto μE-CD was obtained.     

Green Composite Based on Silver Nanoparticles Supported on Diatomaceous Earth: Kinetic Adsorption Models and Antibacterial Effect

A green synthesis of composite based on silver nanoparticles (AgNPs) obtained by Melissa officinalis (MO) extract and supported on diatomaceous earth (DE) was synthesized. Kinetic adsorption models were proposed to describe the sorption mechanism of AgNPs nanoparticles during the impregnation process. Theoretical models as pseudo first order, pseudo-second order, Elovich and intraparticle diffusion were developed to establish accurately the kinetic parameters, such as correlations factors (R²) and maximum Ag nanoparticles sorption capacity of the diatomite. According to the Kinetic adsorption parameters obtained, the pseudo-second order model reveals the best linear fit. Also, four types of pseudo-second order model were performed and analyzed. The proposed models describe with great precision, the adsorption mechanism of Ag nanoparticles during the impregnation process onto DE surface. Complementary, the antibacterial activity of the composite against Staphylococcus aureus and Escherichia coli were evaluated. The green composite (Ag nanoparticles/diatomaceous earth) was characterized by Electron Microscopy, X-Ray Diffraction and Infrared Spectroscopy.     

Effects of inherent/enhanced solid acidity and morphology of diatomite templates on the synthesis and porosity of hierarchically porous carbon

The inherent or enhanced solid acidity of raw or activated diatomite is found to have significant effects on the synthesis of hierarchically porous diatomite-templated carbon with high surface area and special porous structure. The solid acidity makes raw/activated diatomite a catalyst for the generation of porous carbon, and the porous parameters of the carbon products are strongly dependent on the solid acidity of diatomite templates. The morphology of diatomite also dramatically affects the textural structure of porous carbon. Two types of macroporous structures in the carbon product, the partially solid pillars and the ordered hollow tubes, derive from the replication of the central and the edge pores of diatom shell, respectively. The hierarchically porous carbon shows good capability for the adsorption of solvent naphtha and H(2), enabling potential applications in adsorption and gas storage.     

Infrared spectral investigations of adsorption and oxidation of N,N-dimethylaniline by sepiolite,loughlinite and diatomite

The adsorption behaviour of sepiolite, loughlinite (Nasepiolite) and diatomite for N,N-dimethylaniline (DMA) and its catalytically formed oxidation products are studied using IR spectroscopy. It is found that sepiolite and loughlinite adsorb DMA and then react with it more easily than diatomite. The adsorption capacity sequence of DMA for the minerals studied is sepiolite > loughlinite > diatomite.     

On uranium(VI) adsorption on activated carbon

The uranium adsorption on activated carbon from dilute solutions was studied as a function of pH, uranium concentration and ageing time. Optimum conditions for quantitative adsorption of uranium from water solutions were determined: uranium concentration 2.5.10⁻⁴ g/l or less; adsorption must be carried out in fresh prepared solutions with ageing time not more than one hour; pH 7.5–8.5; time for achieving the adsorption equilibrium not less than 20 min. The instrumental neutron activation method was used for the uranium analysis.     

硅藻土增强橡胶复合材料的研究进展

硅藻土是单细胞硅藻的遗骸经自然条件形成的硅质沉积岩,因其具有质轻、大的比表面积、超强的吸附性、隔音、耐磨、耐热以及耐腐蚀等特点而被广泛应用于化工、石油、建材、生物医药卫生以及环保等众多领域。然而由于硅藻土与白炭黑的结构成分相似,白炭黑通常用作橡胶的补强填料,目前硅藻土用于橡胶补强填料的研究鲜少报道。本文综述了硅藻土的性能、硅藻土的国内外研究现状、硅藻土的改性以及硅藻土增强橡胶复合材料的制备过程,并对硅藻土增强橡胶复合材料的发展趋势做了展望。     

Diglycolamide functionalized multi-walled carbon nanotubes for removal of uranium from aqueous solution by adsorption

Diglycolamide functionalized multi-walled carbon nanotubes (DGA-MWCNTs) were synthesized by sequential chemical reactions for removal of uranium from aqueous solution. Characterization studies were carried out using FT-IR spectroscopy, XRD and SEM analysis. Adsorption of uranium from aqueous solution on this material was studied as a function of nitric acid concentration, adsorbent dose and initial uranium concentration. The uranium adsorption data on DGA-MWCNTs followed the Langmuir and Freundlich adsorption isotherms. The adsorption capacity of DGA-MWCNTs as well as adsorption isotherms and the effect of temperature on uranium ion adsorption were investigated. The standard enthalpy, entropy, and free energy of adsorption of the uranium with DGA-MWCNTs were calculated to be 6.09 kJ mole⁻¹, 0.106 kJ mole⁻¹ K⁻¹ and −25.51 kJ mole⁻¹ respectively at 298K. The results suggest that DGA-MWCNTs can be used as efficient adsorbent for uranium ion removal.     

Adsorption of uranium from aqueous solution by graphene oxide nanosheets supported on sepiolite

Adsorptive behavior of uranium from aqueous solution on graphene oxide supported on sepiolite composites (GO@sepiolite composites) as a function of pH, ionic strength, temperature and initial uranium concentration was carried out by the batch techniques. GO@sepiolite composites was synthesized and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and potentiometric acid–base titration. According to XRD patterns and SEM images, the graphene oxide nanosheets were grafted on sepiolite surface successfully. The macroscopic results showed that the adsorption of uranium on GO@sepiolite composites was significantly depended on pH, whereas no effect of ionic strength on uranium adsorption at high pH and high ionic strength conditions was observed. The uptake equilibrium is best described by Langmuir adsorption isotherm, and the maximum adsorption capacity (Q_e) of GO@sepiolite composites at pH 5.0 and T = 298 K were calculated to be 161.29 mg/g. Thermodynamic results indicated that the adsorption of uranium on GO@sepiolite composites is the spontaneous and exothermic process.     

Hydrothermal leather waste by hydrothermal method for uranium (VI) removal from a Simulated Saline Solution

Hydrothermal leather waste was prepared by hydrothermal method, using leather waste as the precondition and applying the adsorption of uranium (VI) in solution. The effects of pH value, adsorption time and initial concentration of uranium (VI) on the adsorption efficiency were investigated. The adsorption process was in accordance with the pseudo‐second‐order kinetic model and Freundlich adsorption isotherm model. Kinetic and thermodynamic studies showed that the adsorption process was endothermic and spontaneous, and it reached adsorption equilibrium in 240 min. In the simulated high salinity environment, the adsorbent exhibited excellent adsorption rate on the trace of uranium (VI). The adsorbent was characterized by scanning electron microscopy, flourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy, and it was found that the adsorption mechanism was coordinated complex.     

Kinetic studies of uranium(VI) adsorption on a composite ion exchanger

In this paper, we studied the continuous adsorption of uranium on a composite ion exchanger. The experimental study was carried out at optimum conditions of uranium uptake found in the previous study. For these conditions first the adsorption isotherm was determined. This isotherm shows non-linear sorption according to the Langmuir model. Then we investigated uranium adsorption at different time intervals at temperatures of 30°C and 60°C, respectively.