Strong adsorption of phosphate by amorphous zirconium oxide nanoparticles

Phosphate removal is important in the control of eutrophication of water bodies. Adsorption is one of the promising approaches for the removal of phosphate, which could serve as a supplement for the biological phosphate removal process commonly used in the wastewater treatment industry to meet the discharge requirement when the biological performance is deteriorated from changes of operation conditions. Amorphous zirconium oxide nanoparticles were synthesized by a simple and low-cost hydrothermal process, and their phosphate removal performance was explored in aqueous environment under various conditions. A fast adsorption of phosphate was observed in the kinetics study, and their adsorption capacity was determined at about 99.01 mg/g at pH 6.2 in the equilibrium adsorption isotherm study. Commonly coexisting anions showed no or minimum effect on their phosphate adsorption performance. The phosphate adsorption showed little pH dependence in the range from pH 2 to 6, while it decreased sharply with the pH increase above pH 7. After adsorption, phosphate on these am-ZrO₂ nanoparticles could be easily desorbed by NaOH solution washing. Both the macroscopic and microscopic techniques demonstrated that the phosphate adsorption mechanism of am-ZrO₂ nanoparticles followed the inner-sphere complexing mechanism, and the surface hydroxyl groups played a key role in the phosphate adsorption.     

改性炭对磺胺甲噁唑的吸附及解吸特性

采用商品活性炭和金属氧化物改性炭作为吸附剂,研究了几种活性炭对磺胺甲噁唑(SMZ)的吸附及解吸特性。结果表明:SMZ在几种活性炭上的吸附动力学符合拟二级动力学方程;SMZ的吸附均可采用Freundlich、Langmuir和Langmuir-Freundlich模型进行拟合,Langmuir-Freundlich吸附模型能更好地描述活性炭和改性炭对SMZ的吸附行为;铁、锰氧化物的存在对活性炭的比表面或者孔结构影响不大,并且其对活性炭吸附水中SMZ的性能影响甚微;与AC-Fe和AC-Mn相比,AC-0上吸附的SMZ更易解吸,改性炭负载的金属氧化物与SMZ的表面络合作用增强了AC-Fe和AC-Mn对SMZ的化学吸附,并且改性炭的MnOx和FeOx能氧化降解部分SMZ。     

The use of hydrous iron (III) oxides for the removal of hydrogen sulphide in aqueous systems

The potential for iron (hydr)oxides to remove dissolved hydrogen sulphide from seawater has been examined under flow-through conditions. Ferrihydrite (a hydrous iron (III) oxide) was stabilised by precipitation onto zeolite pellets, and rates of sulphide removal were determined under laboratory conditions at pH 8.5. Sulphide removal kinetics were dependent on the initial sulphide concentration, substrate mass and flow rate. The experimental data suggest that these parameters can be optimised to result in the rapid and effective removal of hydrogen sulphide. The results from laboratory experiments compared favourably with sulphide removal kinetics determined in a series of experiments performed online in a recirculating mariculture production system. However, the presence in solution of ligands such as phosphate may also significantly affect reaction rates; a 50% reduction in sulphide removal rate for substrate removed from an online system was partly attributed to phosphate adsorption. The formation of a more crystalline, less reactive iron (hydr)oxide in recharged substrate was the likely result of FeS oxidation, which may also have contributed to the observed reduction in sulphide removal rates. Ferrihydrite-coated zeolite would appear to provide an efficient, low-cost method for sulphide removal, which is particularly suited to relatively small-scale aqueous flow-through systems. The reaction of iron (hydr)oxides with dissolved sulphide is also accompanied by a distinct colour change due to the formation of black FeS(s) which, under appropriate conditions, may be used as a rapid indicator of sulphidic conditions.     

Desorption of dye from activated carbon beds: effects of temperature, pH, and alcohol.

The adsorption isotherms of yellow and red dye solutions onto granular activated carbon at varying solution pHs (2-8). temperatures (15-50 degrees C), and alcohol concentrations (0-20%) were experimentally determined by batch tests and the Tóth model was found to best fit the adsorption isotherm data for varying solution pHs. temperatures, and alcohol concentrations. The maximum adsorption capacity was found to decrease with increasing solution pH and alcohol concentration and could be predicted by the correlation equations obtained in this study. A correlation equation was also obtained to account for the effects of solution temperature on the adsorption equilibrium constant. The 25 degrees C water was found to be a very poor regenerant for the carbon bed presaturated with the yellow dye compared with 20% alcohol solution. A simple equation was derived, based on non-linear wave propagation theory, to predict the desorption curves of activated carbon bed. Given presaturation concentration, bed density and void fraction, and adsorption isotherm, the wave propagation theory predicted the desorption curves quite satisfactorily.     

活性氧化铝吸附水中As(V)的实验研究

通过静态实验研究了活性氧化铝对水中As(V)的吸附性能,分析了吸附As(V)动力学、吸附等温线以及不同pH和溶液中共存离子的影响.结果表明:活性氧化铝吸附As(V)的最佳pH为4~6,在pH为5.5左右的时候达到最大去除率99%;受氟离子、碳酸根离子和磷酸根离子影响较大,硝酸根和硫酸根基本无影响,而氯离子有促进吸附的效果;可用Langmuir吸附等温线很好地拟合,属于单分子层吸附,最大吸附量为15.7mg/g;其动力学符合Lagergren二级动力学模型.     

改性钢渣的制备及其吸附除磷性能

研究了改性钢渣吸附除磷影响因素、等温吸附线特征和吸附动力学,并对生物处理后的出水进行吸附除磷研究。结果表明:在初始磷浓度10mg/L,投加量10g/L、pH为7时,改性钢渣吸附后总磷浓度为0.687mg/L,去除率达93%;改性钢渣对磷的吸附符合Langmuir模型,理论饱和吸附量是1.977mg/g,吸附动力学符合准二级动力学模型(R20.99);实际生活污水的吸附除磷中,投加量为50g/L,反应2h后出水总磷浓度达到《城镇污水处理厂污染物排放标准》(GB18918—2002)一级B标的排放要求。     

氢氧化铁对水中砷的吸附试验研究

就氢氧化铁对As(Ⅲ)的吸附动力学、吸附等温线以及pH和温度等影响因素进行了研究。结果表明:氢氧化铁对As(Ⅲ)的吸附动力学符合Lagergren二级吸附动力学模型,其吸附等温线可用Langmuir方程很好地描述,即属于单分子层吸附,试验得到的饱和吸附量为9.09mg/g;pH值在4.1~8.5内,氢氧化铁对As(Ⅲ)的去除率较高,保持在70%以上,超出这个范围,氢氧化铁对As(Ⅲ)的去除率逐渐降低,pH值为6.8左右时,氢氧化铁对As(Ⅲ)的去除率达到最高,约为94.8%;随着温度的升高,氢氧化铁对As(Ⅲ)的吸附率逐渐降低,在0~25℃时,氢氧化铁对As(Ⅲ)的去除率保持在80%以上。     

Impact of pH on the adsorption and desorption kinetics of 2-nitrophenol on activated carbons

The adsorption and desorption kinetics of 2-nitrophenol (2NP) from aqueous solutions using F-400 and WV-B granular activated carbons (GAC) have been studied at pHs 1, 4.6 and 13, using batch tests. Adsorption and desorption kinetics of 2NP on to both carbons were adequately described by the homogeneous solid surface diffusion model (HSSD). The adsorption and desorption kinetics can be predicted at different pHs by using adsorption kinetics parameters of the pH 4.6 and the isotherm parameters for the corresponding pH. Thus, the differences in the rates of adsorption are primarily attributable to the differences in the equilibrium loadings at the various pHs.     

Removal of zinc, copper and lead by natural zeolite-a comparison of adsorption isotherms

An uptake of zinc (Zn), copper (Cu), and lead (Pb) from aqueous solutions by ion exchange on natural zeolitic tuff has been studied. The Croatian zeolite clinoptilolite from the Donje Jesenje deposit has been used as a natural ion exchanger. The efficiency of removal is higher for Pb and Cu than for Zn ions. Measured concentrations of Si in the liquid phase identify the detachment of the aluminosilicate structure during ion exchange in the presence of H(+) and OH(-) ions. The adsorption isotherm equations; Langmuir-Freundlich, Redlich-Petersen, Toth, Dubinin-Radushkevich, modified Dubinin-Radushkevich, and Lineweawer-Burk were derived from the basic empirical equations, and used for calculation of ion exchange parameters. The best fitting of experimental results to the proposed isotherms was observed in models that assume that ionic species bind first at energetically most favorable sites, with multi-layer adsorption taking place subsequently.     

Preparation and evaluation of a novel Fe-Mn binary oxide adsorbent for effective arsenite removal

Arsenite (As(III)) is more toxic and more difficult to remove from water than arsenate (As(V)). As there is no simple treatment for the efficient removal of As(III), an oxidation step is always necessary to achieve higher removal. However, this leads to a complicated operation and is not cost-effective. To overcome these disadvantage, a novel Fe-Mn binary oxide material which combined the oxidation property of manganese dioxide and the high adsorption features to As(V) of iron oxides, were developed from low cost materials using a simultaneous oxidation and coprecipitation method. The adsorbent was characterized by BET surface areas measurement, powder XRD, SEM, and XPS. The results showed that prepared Fe-Mn binary oxide with a high surface area (265 m2 g(-1)) was amorphous. Iron and manganese existed mainly in the oxidation state +III and IV, respectively. Laboratory experiments were carried out to investigate adsorption kinetics, adsorption capacity of the adsorbent and the effect of solution pH values on arsenic removal. Batch experimental results showed that the adsorbent could completely oxidize As(III) to As(V) and was effective for both As(V) and As(III) removal, particularly the As(III). The maximal adsorption capacities of As(V) and As(III) were 0.93 mmol g(-1) and 1.77 mmol g(-1), respectively. The results compare favorably with those obtained using other adsorbent. The effects of anions such as SO4(2-), PO4(3-), SiO3(2-), CO3(2-) and humic acid (HA), which possibly exist in natural water, on As(III) removal were also investigated. The results indicated that phosphate was the greatest competitor with arsenic for adsorptive sites on the adsorbent. The presence of sulfate and HA had no significant effect on arsenic removal. The high uptake capability of the Fe-Mn binary oxide makes it potentially attractive adsorbent for the removal of As(III) from aqueous solution.