Removal of Pb(II) from water using keratin colloidal solution obtained from wool

The aim of this study is to investigate the use of keratin colloidal solution, which was obtained from wool, for the removal of Pb(II) from water. The addition of keratin colloidal solution (15 g L^?1, 0.30 mL) to a Pb(II) solution (1.0 mM, 0.90 mL, pH 5.0) resulted in the formation and precipitation of a Pb–keratin aggregate. Measurement of the Pb(II) and protein concentrations in the supernatant solution revealed that 88 and 99 % of the Pb(II) and keratin protein were removed from the solution, respectively. The maximum Pb(II) uptake capacity of keratin in the colloidal solution was 43.3 mg g^?1. In addition, the Pb–keratin aggregate was easily decomposed via the addition of nitric acid, which enabled the recovery of Pb(II). However, aggregation did not occur in solutions with Pb(II) concentrations below 0.10 mM. Therefore, we used a keratin colloidal solution encapsulated in a dialysis cellulose tube to remove Pb(II) from 0.10 mM solutions, which enabled the removal of 95 % of the Pb(II). From these results, we conclude that keratin colloidal solution is useful for the treatment of water polluted with Pb(II).     

Accumulation of chromium (VI) from aqueous solutions using water lilies (Nymphaea spontanea)

This study describes an investigation using tropical water lilies (Nymphaea spontanea) to remove hexavalent chromium from aqueous solutions and electroplating waste. The results show that water lilies are capable of accumulating substantial amount of Cr(VI), up to 2.119 mg g(-1) from a 10 mg l(-1) solution. The roots of the plant accumulated the highest amount of Cr(VI) followed by leaves and petioles, indicating that roots play an important role in the bioremediation process. The maturity of the plant exerts a great effect on the removal and accumulation of Cr(VI). Plants of 9 weeks old accumulated the most Cr(VI) followed by those of 6 and 3 weeks old. The results also show that removal of Cr(VI) by water lilies is more efficient when the metal is present singly than in the presence of Cu(II) or in waste solution. This may be largely associated with more pronounced phytotoxicity effect on the biochemical changes in the plants and saturation of binding sites. Significant toxicity effect on the plant was evident as shown in the reduction of chlorophyll, protein and sugar contents in plants exposed to Cr(VI) in this investigation.     

Removal of PAHs from water using an immature coal (leonardite)

It has been studied an immature coal (leonardite) as an adsorbent for removing PAHs [fluorene, pyrene, benzo(k)fluoranthene, benzo(a)pyrene and benzo(g,h,i)perylene] from water. To determine the efficiency of leonardite as an adsorbent of PAHs, factors such as pH, contact time and equilibrium sorption were evaluated in a series of batch experiments. There were no significant differences in the removal percentages for the various pH values studied, except for fluorene. The adsorption of fluorene was higher at lower pH values. The equilibrium time was reached at 24h. At this time, more than 82% of the pyrene, benzo(k)fluoranthene, benzo(a)pyrene and benzo(g,h,i)perylene had been removed. During the first 2h, the adsorption rate increased rapidly. After that time, however, there was a minor decrease. Equilibrium data were fitted to Freundlich models to determine the water-leonardite partitioning coefficient. Physical adsorption caused by the aromatic nature of the compounds was the main mechanism that governed the removal process. The polarity of the humic substances in leonardite may also have influenced the adsorption capacity.     

粉煤灰复合氧化钙去除铬渣渗滤液中的总铬

粉煤灰虽然具有较大的比表面积,但单独做为处理剂处理含铬废水,效果并不理想,具有吸附容量小、溶解损失大、且有毒性浸出等特点.为了解决粉煤灰以上缺陷,提出氧化钙复合粉煤灰去除铬渣渗滤液中总铬的技术,研究表明,在室温25℃条件下,总铬初始浓度在0.30~80.00 mg/L范围内,选择粉煤灰与CaO配比为1:1时,以150 r/min转速充分振荡24 h,总铬去除率均能达到90%以上.通过空白对照实验研究表明,粉煤灰复合CaO使用,对总铬的去除远优于单独使用粉煤灰或CaO做为吸附剂的处理效果.利用SEM,XRD,红外光谱分析3种材料表征方法,对粉煤灰原料、CaO-粉煤灰处理后残渣等进行分析,结果表明,在水介质条件下,粉煤灰与CaO能生成晶体矿物.当溶液中有铬存在时,晶体矿物在形成的过程中能将铬裹入其结构中.通过浸出实验表明,此晶体矿物对铬具有很好的固定作用.     

Removal of phosphate from water by a highly selective La(III)-chelex resin

A new polymer ligand exchanger (PLE) has been developed for the removal of phosphate in wastewater. This PLE, consisting of lanthanum(III) bound to chelex-100 resin, was prepared by passing LaCl3 solution through a column of chelex-100. Uptake of phosphate from water by this La-chelex resin was investigated in the column mode. The La-chelex resin was able to remove phosphate efficiently from water, and the uptake of phosphate was not affected by the presence of large amounts of anions (0.1M) such as chloride and sulfate. The La-chelex resin was also able to efficiently remove phosphate from seawater to <0.1mg-Pl(-1), and regenerated for reuse by removing the sorbed phosphate by eluting with 6M HCl.     

Ageing of chromium(III)-bearing slag and its relation to the atmospheric oxidation of solid chromium(III)-oxide in the presence of calcium oxide

Slag arising in ferrochromium and stainless steel production is known to contain residual levels of trivalent chromium. As the chromium is normally bound in the slag matrix in various silicate or spinel phases, and hence not easily mobilised, utilisation or controlled disposal of such slag is generally considered unproblematic. Experimental test work with a number of slag materials indicates, however, that very gradual oxidation of trivalent to hexavalent chromium does occur when the slag is exposed to atmospheric oxygen, rendering a quantifiable but small portion of chromium in this much more mobile and toxic form. Mechanisms and rates of the oxidation reaction were investigated in a number of long-term studies using both original slag materials and artificial mixes of chromium and calcium oxides. Powders of these materials, some of them rolled into balls, were left to age under different conditions for periods of up to 12 months. In the slag samples, which contained between 1 and 3 wt.% chromium, 1000–10 000 μg Cr(VI) were found per gram of chromium within 6–9 months of exposure to an ambient atmosphere. The rate of the oxidation reaction decreased exponentially, and the reaction could generally be said to have ceased within 12 months. In mixtures of calcium and chromium oxides the oxidation reaction is presumed to occur at the boundaries between chromium oxide and calcium oxide phases through diffusion of oxygen along the grain boundaries and of Cr³⁺ across the boundaries, resulting in the formation of calcium chromate. In the slags, where calcium and chromium oxide can form a solid solution, the oxidation is likely to occur at the exposed surface of grains containing this solution.     

改性天然菱铁矿去除水中六价铬

六价铬Cr(Ⅵ)是地下水污染的重要组分之一。近几年吸附法除铬被广泛应用。为了强化Cr(Ⅵ)的去除效率,对成本低廉的天然菱铁矿进行了改性,并研究了最优改性条件及其对Cr(Ⅵ)的吸附特性。经过不同温度的灼烧改性发现,在500℃灼烧20 min时改性材料去除地下水中Cr(Ⅵ)的效率最高,在25℃时其吸附容量可达0.092 mg/g,吸附效率为92%。通过一系列的静态批实验,考察了最优改性菱铁矿对水中Cr(Ⅵ)的吸附效果。结果表明,二级吸附动力学模型可以更好地描述不同温度下的吸附过程。与Langmuir等温吸附模型相比,等温吸附数据更好地符合Freundlich等温吸附模型。溶液pH对改性天然菱铁矿的吸附效果影响较大,pH在2~8之间吸附容量基本稳定;当pH=8~11时,随着pH升高吸附量明显减小。SEM、比表面积、ZPC测定等结果表明,改性菱铁矿比表面积增大,pHzpc在7.8左右。因此,比表面积、表面电荷的分布等表面性质是改性天然菱铁矿除铬性能强的主要原因。     

Removal of fluoride from water by using a coagulant (inorganic polymeric coagulant)

Environmental Science and Pollution Research - Excess fluoride (F) ion of drinking water is a major problem in many areas of India and causes harmful effects such as dental and skeletal fluorosis....     

Removal of As(III) and As(V) from water by chitosan and chitosan derivatives: a review

As arsenic removal becomes a global concern, the development of removal processes for arsenic treatment is still a major challenge. With regard to environmental compatibility and cheapness, chitosan and chitosan derivatives are considered as a promising removal technology for arsenic. Chitosan and chitosan derivatives possess the properties of low cost and good sorption on the arsenic removal. The present review is concerned about the present understanding of the mechanisms involved in sorption processes. Further on, detailed discussions are given of the effects of various factors on the performance of chitosan and chitosan derivatives in arsenic treatment processes. Finally, special attention is paid to the future challenges of chitosan and chitosan derivatives utilized for industrial arsenic treatment.     

Adsorption mechanism of chromium(III) using biosorbents of Jatropha curcas L.

Environmental Science and Pollution Research - The removal of Cr3+ from water solutions by biosorbents from the rind, endosperm, and endosperm + episperm of the Jatropha curcas was evaluated....     

Removal of As(III) and As(V) using iron-rich sludge produced from coal mine drainage treatment plant

To test the feasibility of the reuse of iron-rich sludge (IRS) produced from a coal mine drainage treatment plant for removing As(III) and As(V) from aqueous solutions, we investigated various parameters, such as contact time, pH, initial As concentration, and competing ions, based on the IRS characterization. The IRS consisted of goethite and calcite, and had large surface area and small particles. According to energy dispersive X-ray spectroscopy mapping results, As was mainly removed by adsorption onto iron oxides. The adsorption kinetic studies showed that nearly 70 % adsorption of As was achieved within 1 h, and the pseudo-second-order model well explained As sorption on the IRS. The adsorption isotherm results agreed with the Freundlich isotherm model, and the maximum adsorption capacities for As(III) and As(V) were 66.9 and 21.5 mg/g, respectively, at 293 K. In addition, the adsorption showed the endothermic character. At high pH or in the presence of phosphate, the adsorption of As was decreased. When the desorption experiment was conducted to reuse the IRS, 85 % As was desorbed with 1.0 N NaOH. In the column experiment, adsorbed As in real acid mine drainage was 43 % of the maximum adsorbed amount of As in the batch test. These results suggested that the IRS is an effective adsorbent for As and can be effectively applied for the removal of As in water and wastewater.     

Removal of hydrogen chloride from gaseous streams using magnesium-aluminum oxide

Magnesium-aluminum oxide (Mg-Al oxide) obtained by thermal decomposition of Mg-Al layered double hydroxide (Mg-Al LDH) effectively removed HCl from gaseous streams. HCl removal was greater in the presence of added water vapor at all temperatures examined and increased with decreasing temperature in both the presence and absence of added water vapor. Wet and dry removal of gaseous HCl were attributed to the production of MgCl2 . 6H2O and MgCl2 . 4H2O, respectively. For the wet scrubbing process, the reconstruction reaction of Mg-Al LDH from Mg-Al oxide was the primary mechanism for increased HCl removal.     

PBTCA稳定零价纳米铁的制备及其去除水中Cr(Ⅵ)

以2-膦酸丁烷-1,2,4三羧酸(PBTCA)为稳定剂,通过FeCl3.6H2O与NaBH4反应,利用液相还原法制备稳定纳米级零价铁颗粒(P-NZVI),并用透射电子显微镜(TEM)、扫描电子显微镜(SEM)及X射线衍射(XRD)进行表征,颗粒平均粒径为73 nm。考察了Cr(Ⅵ)溶液初始浓度、pH、NZVI投加量、温度等条件对Cr(Ⅵ)去除效果的影响,并与同等条件下不加稳定剂制备的纳米铁(N-NZVI)进行对比。结果表明:Cr(Ⅵ)的去除率随温度和纳米铁投加量增加而升高,随pH和Cr(Ⅵ)溶液初始浓度升高而降低。在相同实验条件下,P-NZVI对Cr(Ⅵ)的去除效果明显优于N-NZVI,表明改性后纳米铁在地表水原位修复领域具有较好的应用前景。     

生物炭负载羧甲基纤维素钠稳定化纳米铁对水中六价铬的去除

利用液相还原法,通过先负载再包裹的方式制备了4种不同炭铁质量比的生物炭负载羧甲基纤维素钠稳定化纳米铁(BC-nZVI-CMC)材料,并将其用于对水中Cr(Ⅵ)的去除,使用扫描电镜、X射线衍射和傅里叶红外等技术对BC-nZVI-CMC的结构与性质进行了表征。结果表明：BC-nZVI-CMC具有较好的分散性,粒径为纳米级且被CMC完全包覆,抗氧化能力得到较大提升,可有效去除水中Cr(Ⅵ);投加1 g·L⁻¹的BC-nZVI-CMC对含有30 mg·L⁻¹的Cr(Ⅵ)去除率达99.83%;pH越小,越有利于BC-nZVI-CMC对水中Cr(Ⅵ)的去除,最高去除率可达100%;BC-nZVI-CMC的抗氧化能力明显高于商品纳米铁和生物炭负载纳米铁;含有8 g·L⁻¹ C/Fe=1∶1的BC-nZVI-CMC对电镀废水中Ni、Zn、Cu、总铬、Cr(Ⅵ)的去除率可达39.60%、91.70%、100%、91.69%、100%。上述研究结果对水中Cr(Ⅵ)去除新技术的开发有重要的参考价值。     

吸水凝胶包覆型纳米零价铁对水中土霉素的去除

为解决纳米零价铁(nZVI)在应用中易团聚、易氧化的局限,以聚丙烯酸钠和聚丙烯酰胺的共聚物(PPAA)为载体,以茶多酚为还原剂,采用绿色合成法制备吸水凝胶包覆型纳米零价铁(PPAA-nZVI),并将其用于水中土霉素(OTC)的去除。通过SEM、BET、FTIR和XPS等表征了PPAA-nZVI的微观形貌和物化性质,探讨了OTC初始质量浓度、溶液初始pH和共存物质对OTC去除效果的影响。结果表明,茶多酚能够还原制备nZVI,且成功将nZVI负载到PPAA内。随着初始OTC质量浓度的增加,OTC的去除率逐渐增加,当PPAA-nZVI投加量为0.5 g·L⁻¹、OTC初始质量浓度为300 mg·L⁻¹时,材料对OTC的去除量达到最大481 mg·g⁻¹。pH对材料去除OTC的影响较小。PO₄³⁻和HA的存在对PPAA-nZVI去除OTC均有抑制作用。材料去除OTC主要通过Fenton氧化、OTC与Fe³⁺的络合以及材料表面活性位点的吸附3种途径。以上研究结果可为nZVI在净化污染水体中的OTC提供一种有前景的方法。     

Removal of Cr(VI) onto Ficus carica biosorbent from water

The utilization of sustainable and biodegradable lignocellulosic fiber to detoxify the noxious Cr(VI) from wastewater is considered a versatile approach to clean up a contaminated aquatic environment. The aim of the present research is to assess the proficiency and mechanism of biosorption on Ficus carica bast fiber via isotherm models (Langmuir, Freundlich, Temkin, Harkin’s–Jura, and Dubinin–Radushkevich), kinetic models, and thermodynamic parameters. The biomass extracted from fig plant was characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. To optimize the maximum removal efficiency, different parameters like effect of initial concentration, effect of temperature, pH, and contact time were studied by batch method. The equilibrium data were best represented by the Langmuir isotherm model, and the maximum adsorption capacity of Cr(VI) onto biosorbent was found to be 19.68 mg/g. The pseudo-second-order kinetic model adequately described the kinetic data. The calculated values of thermodynamic parameters such as enthalpy change (?H ⁰), entropy change (?S ⁰), and free energy change (?G ⁰) were 21.55 kJ/mol, 76.24 J/mol?K, and ?1.55 kJ/mol, respectively, at 30 °C which accounted for spontaneous and endothermic processes. The study of adsorbent capacity for Cr(VI) removal in the presence of Na⁺, Mg²⁺, Ca²⁺, SO ₄ ^2? , HCO ₃ ^? and Cl^? illustrated that the removal of Cr(VI) increased in the presence of HCO^3? ions; the presence of Na⁺, SO ₄ ^2? or Cl^? showed no significant influence on Cr(VI) adsorption, while Ca²⁺ and Mg²⁺ ions led to an insignificant decrease in Cr(VI) adsorption. Further, the desorption studies illustrated that 31.10 % of metal ions can be removed from an aqueous system, out of which 26.63 % of metal ions can be recovered by desorption in first cycle and the adsorbent can be reused. The results of the scale-up study show that the ecofriendly detoxification of Cr(VI) from aqueous systems was technologically feasible.     

香蒲根际过滤对水中镉的去除

通过水培实验,研究香蒲根系对水中镉的根际过滤效果及富集量。结果表明：在镉浓度1 mg·L-1的静止水体中,香蒲根际过滤对镉的去除率为66%;在相同镉浓度并且水力停留时间为8 h的流动水体中,镉去除率为52%。香蒲体内富集的镉约90%集中在根部,且第1天镉的去除速率最快,镉浓度以约0.1 mg·h-1速率下降;在静止水体中,香蒲根系7 d对镉的富集量为682.99 mg·kg-1（DW）,动态水体中香蒲根系富集量达1 096.94 mg·kg-1,可有效去除水中的镉。     

MnO2@矿渣去除废水中的铊

以工业磁性矿渣构建具有二氧化锰包覆层（MnO2@矿渣）的吸附剂,用于去除废水中的重金属铊元素。并探究吸附剂投加量、反应时间、反应pH、离子强度、有机物等影响因素及除铊机理。结果表明：在碱性条件下（pH=10）,MnO2@矿渣对水中的铊的吸附率达99.5%以上,10 min 内达到吸附平衡; MnO2@矿渣对铊的吸附容量随投加量的增大而增大,随离子强度的增大而减小,有机物对吸附铊的影响表现出差异性。吸附过程符合拟二级动力学模型,等温吸附适用Langmuuir和Freundlich方程描述;通过X-射线粉末衍射（XRD）、扫描电子显微镜（SEM）-X射线能谱（EDS）表征手段分析,证实成功制备了MnO2@矿渣;傅里叶变换红外（FT-IR）和X射线光电子能谱（XPS）的结果表明MnO2@矿渣对Tl（I）的去除是一个表面羟基络合、氧化和沉淀的过程。重复利用实验表明MnO2@矿渣有很好的脱附与再生能力。     

模拟酸雨对氧化锰吸附砷(Ⅲ)的解吸行为研究

以合成的氧化锰为吸附剂研究了酸雨pH值、酸雨离子强度、解吸时间和解吸次数等因素对模拟酸雨解吸砷(Ⅲ)的影响。实验结果表明:氧化锰对砷(Ⅲ)吸附容量较大,等温平衡吸附量为:48.38 mg/g。模拟酸雨的pH值与离子强度对砷(Ⅲ)的解吸影响不大;解吸反应在90 min后基本达到平衡,平衡解吸量为2.69×10-2mg/g;随解吸次数的增加解吸量变化不大。氧化锰对砷(Ⅲ)的吸附主要是专性的配位吸附,吸附砷(Ⅲ)后难以被模拟酸雨解吸。     

Removal of 2-chlorophenol from water using rice-straw derived ash

Removal of 2-chlorophenol from water using rice-straw derived ash (RSDA) was evaluated in this study to compare with commercial activated carbon. RSDA was obtained by burning rice-straw at 400 °C and 700 °C for 1 h. This ash can provide a better adsorbent for 2-chlorophenol. The adsorption capacities of RSDA at 400 °C and 700 °C are 37 and 52 mg g?1 at pH 4, respectively, and decrease to 9.0 and 40 mg g?1 at pH 10. Adsorption of either neutral or anionic 2-cholorphenol by the RSDA are shown as L-shaped nonlinear isotherms, suggesting surface adsorption rather than partitioning is occurring. At higher-burning temperatures, the surface area, porosity, point of zero charge and aromaticity of the resultant RSDA increase, but the oxygen content and surface acidity decrease. The combined effects result in a higher 2-chlorophenol adsorption of RSDA at 700 °C, which shows a slight pH effect on the adsorption of 2-chlorophenol, due to the lower content of oxygen-containing functional groups. Oxygen-containing functional groups contribute to surface acidity and H-bonding sites for adsorbed water, which compromises the interaction between 2-chlorophenol and the adsorbents. Thus, it suggests that rice-straw derived carbon (RSDC) can be used as an effective low-cost substitute material for activated carbon for removal of chlorophenols from wastewater.