纤维素/硅藻土复合气凝胶的吸附性能

以纤维素与硅藻土为原料制备纤维素/硅藻土复合气凝胶。研究了影响纤维素/硅藻土复合气凝胶吸附的因素,以及复合气凝胶吸附亚甲基蓝的等温曲线、动力学与热力学特性。结果表明,纤维素/硅藻土复合气凝胶中硅藻土最佳含量为0.5 g,随着pH值的提高,纤维素/硅藻土复合气凝胶吸附量增大,碱性条件下最好。纤维素/硅藻土复合气凝胶的吸附量符合Langmuir及伪二级动力学模型,最大吸附量为68.399 5 mg/g。热力学研究表明,纤维素/硅藻土复合气凝胶吸附亚甲基蓝是自发、放热的物理吸附过程。     

木质素基水凝胶对亚甲基蓝染料的吸附性能

以木质素磺酸钠(LS-Na)、2-丙烯酰胺基-2-甲基丙磺酸(AMPS)、丙烯酸(AA)为原料,采用微波辐射法,通过接枝共聚反应合成了生物质LS-g-PAMPS/AA水凝胶吸附剂,利用FTIR分析了水凝胶的结构。研究了吸附剂用量、染料初始浓度、吸附时间对亚甲基蓝(MB)染料的吸附性能的影响,结果显示,在MB初始浓度为1 000 mg/L,吸附剂为0.1 g时,吸附量和吸附率分别达1 914 mg/g和95%。平衡吸附数据满足Langmuir吸附等温模型,吸附动力学曲线较好地符合准二级动力学反应模型。木质素水凝胶对MB染料废水具有显著的吸附效果,可以作为阳离了染料废水处理用的生物质吸附剂。     

生物炭/铁酸镧磁性复合材料的制备及对亚甲基蓝的吸附性能

为获得吸附性能良好、便于回收利用的新型吸附剂以处理染料废水,采用超声辅助溶胶-凝胶法将铁酸镧(LaFeO_3)经过一步热解负载于生物炭制得生物炭/LaFeO_3磁性复合材料(BC/FL)。其表面形态、结构和组成分析表明:BC/FL的比表面积、总孔容及平均孔径分别为34.67m2/g、0.041cm3/g和7.82nm,磁饱和强度达到40.283A/m,表面含有C=O、C=C=N、C≡C等官能团。批量吸附实验表明,25℃下,当亚甲基蓝(MB)的初始质量浓度为30mg/L时,BC/FL的最佳投加量为1.5g/L,吸附反应在120min达到平衡,去除率可达92.3%,且吸附效果基本不受pH影响。BC/FL对MB的吸附符合准二级动力学模型,Langmuir模型可描述其等温吸附过程。化学吸附占主导地位,主要机理为静电吸附、氢键和π-π共轭作用。吸附反应为单分子层吸附且为自发的吸热过程。     

给水厂污泥吸附Cr(Ⅵ)的性能研究

采用给水厂污泥对浓度为100 mg/L的模拟含Cr(Ⅵ)废水进行了吸附性能的研究.结果表明,给水厂污泥可吸附处理含Cr(Ⅵ)废水,吸附量可达0.89 mg/g.动力学研究结果表明,给水厂污泥对Cr(Ⅵ)的吸附符合二级吸附动力学模型,吸附速率常数(k2)为3.48×10-3g/(mg·min);热力学研究结果表明,吸附过...     

半-IPN羧甲基纤维素/聚(丙烯酰胺-共-甲基丙烯酸钠)水凝胶制备及其吸附性能

羧甲基纤维素(CMC)水溶液中,通过自由基共聚制备半-互穿网络(IPN)羧甲基纤维素(CMC)/聚(丙烯酰胺-共-甲基丙烯酸钠)(poly(AAm-co-NMR))水凝胶。研究CMC含量对半-IPN水凝胶溶胀率及对甲基紫的吸附性能影响。IPN-0.25、IPN-0.50和IPN-1.00对甲基紫的平衡吸附容量分别为111.0、182.3和237.6 mg/g。分别采用拟一级、拟二级和粒内扩散模型拟合实验数据,结果表明,拟二级动力学模型最符合该体系,其相关系数R2最高,说明水凝胶对甲基紫的吸附主要为化学吸附。     

浸渍-碱性微波法载磁活性炭粉对壬基酚的吸附

利用浸渍-碱性微波法制备载磁粉末活性炭,通过等温吸附实验和动力学吸附实验,研究对比了其与原料活性炭、浸渍载铁活性炭对壬基酚的吸附性能。采用氮气吸附仪、FTIR、XRD、国标(GB/T12496.19-1999)邻菲啰啉分光度法及VSM,分别对3种样品进行了物相结构、表面官能团、铁含量及磁性能的分析,并探讨了吸附机理。结果表明,浸渍-碱性微波法载磁活性炭的总孔容及孔隙率均有较大提高;其吸附等温线符合Freundich方程,吸附动力学过程符合准二级动力学方程与孔道内扩散模型,相关系数R2均大于0.900。原活性炭经一定浓度的铁盐溶液浸渍后,铁含量由2%提高到8%。在碱性、N2气氛条件下微波后,铁系物主要存在形式为零价铁和Fe3O4,制得的载磁活性炭饱和磁化强度为1.12 emu/g。     

MCM-41介孔分子筛的合成及其对铜离子的吸附性能

以微硅粉为硅源,CTAB和PEG-6000为模板剂,合成MCM-41介孔分子筛。采用XRD、N2吸附-脱附曲线、FT—IR以及TEM表征了其结构、比表面积、孔径分布及晶体形貌,并且以该样品为吸附剂,对含Cu2＋的溶液进行了静态吸附实验。结果表明,以微硅粉为硅源成功合成了具有典型六方排列孔道结构的MCM-41,其比表面积为869．5m。／g,孔容为0．97cm3／g,平均孔径为3．3nm;溶液pH为5—6时,MCM-41对Cu2＋的去除效果最好;MCM-41对Cu3＋的最大吸附吸附容量36．3mg／g;MCM-41对Cu2＋的吸附性能符合Langmuir吸附方程的特征。动力学研究表明,该过程符合准二级动力学模型。     

氨基化凹土对水中焦性没食子酸的吸附

采用氨基硅烷偶联剂(γ-氨丙基三乙氧基硅烷)改性凹凸棒石黏土(以下简称"凹土")为吸附剂,通过静态吸附研究其对模拟废水中焦性没食子酸的吸附性能。结果表明,γ-氨丙基三乙氧基硅烷改性凹土能有效提高凹土的吸附性能,改性凹土吸附50 mL,浓度为100 mg/L焦性没食子酸较理想的条件为吸附剂用量0.4 g、吸附温度20℃、吸附时间40min、体系pH 5.2。通过静态吸附实验数据计算分析得知,拟二级动力学模型比拟一级动力学模型能更好地描述改性凹土对焦性没食子酸的吸附动力学行为,改性凹土对焦性没食子酸的吸附更符合Langmuir等温式,其饱和吸附量为19.861 mg/g。     

多孔水凝胶P(HEA/AMPS)对水溶液中 Fe(Ⅲ) 的吸附

以2-丙烯酸羟乙酯(HEA)和2-丙烯酰胺基-2-甲基丙磺酸(AMPS)为单体合成了聚合物水凝胶(PHEA/AMPS),采用水凝胶对水溶液中Fe(Ⅲ)的吸附行为进行了研究。实验主要考察了聚合物组分、溶液pH、初始Fe(Ⅲ)浓度和吸附时间对水凝胶吸附作用的影响,并通过FT-IR和XPS分析了吸附前后水凝胶的变化。结果表明,当单体摩尔比AMPS∶HEA=1∶1,pH=2时,水凝胶对Fe(Ⅲ)的吸附容量最大。水凝胶对水溶液中Fe(Ⅲ)的吸附容量随着溶液中初始Fe3+浓度的增加而增加,但当初始Fe3+的浓度达到1 g/L时,吸附容量基本达到饱和。吸附等温线符合Langmuir等温线方程,吸附动力学符合准二级模型。FI-IR和XPS的分析表明,水凝胶的磺酸基和酰胺基是吸附Fe3+的有效功能性基团,吸附机理为螯合和离子交换。     

锆(Ⅳ)负载交联壳聚糖吸附硫酸根的性能

以甲醛、苯甲醛为交联剂,制备交联壳聚糖树脂,再与锆(Ⅳ)离子反应制备锆负载交联壳聚糖吸附剂。采用静态吸附法考察了该吸附剂对水中硫酸根离子(SO24-)的吸附性能。实验发现,吸附时间2 h,SO24-溶液初始浓度500 mg/L,pH值3.0,溶液温度35℃为较优的吸附条件;吸附过程符合Langmuir等温吸附模型,属于优惠吸附型,吸附容量可达78.65 mg/g;吸附过程较好地符合拟二级动力学模型;锆负载前后交联壳聚糖对硫酸根的吸附量提高了约4.5倍;该吸附剂具有良好的耐酸性和再生性能。     

Photocatalytic degradation of the herbicide pendimethalin using nanoparticles of BaTiO3/TiO2 prepared by gel to crystalline conversion method: A kinetic approach

Photocatalytic degradation of the herbicide, pendimethalin (PM) was investigated with BaTiO₃/TiO₂ UV light system in the presence of peroxide and persulphate species in aqueous medium. The nanoparticles of BaTiO₃ and TiO₂ were obtained by gel to crystallite conversion method. These photo catalysts are characterized by energy dispersive x-ray analysis (EDX), scanning electron microscope (SEM), x-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) adsorption isotherm and reflectance spectral studies. The quantum yields for TiO₂ and BaTiO₃ for the degradation reactions are 3.166 Einstein m^?2 s^?1 and 2.729 Einstein m^?2 s^?1 and catalytic efficiencies are 6.0444 × 10^?7 mg^?2h^?1L² and 5.403 × 10^?7 mg^?2h^?1L², respectively as calculated from experimental results. BaTiO₃ exhibited comparable photocatalytic efficiency in the degradation of pendimethalin as the most widely used TiO₂ photocatalyst. The persulphate played an important role in enhancing the rate of degradation of pendimethalin when compared to hydrogen peroxide. The degradation process of pendimethalin followed the first-order kinetics and it is in agreement with Langmuir-Hinshelwood model of surface mechanism. The reason for high stability of pendimethalin for UV-degradation even in the presence of catalyst and oxidizing agents were explored. The higher rate of degradation was observed in alkaline medium at pH 11. The degradation process was monitored by spectroscopic techniques such as ultra violet-visible (UV-Vis), infrared (IR) and gas chromatography mass spectroscopy (GC-MS). The major intermediate products identified were: N-propyl-2-nitro-6-amino-3, 4-xylidine, (2, 3-dimethyl-5-nitro-6-hydroxy amine) phenol and N-Propyl-3, 4-dimethyl-2, 6-dinitroaniline by GC-MS analysis and the probable reaction mechanism has been proposed based on these products.     

改性玉米秸秆吸附Cu2+的动力学和热力学

本研究用ZnCl2作为活化剂,使用功率640 W的微波照射4 min的方法制备改性玉米秸秆。考察投加量、pH、吸附时间对吸附性能的影响,并对等温吸附特征、吸附动力学和热力学进行了系统研究。结果表明:投加量为0.2 g,pH为6,改性玉米秸秆对Cu2+具有很好的吸附效果,吸附在8 h后达到平衡。该吸附过程符合Langmuir及Freundlich等温吸附模型和准二级动力学方程,其反应的吉布斯自由能△G<0,为自发反应过程。     

Removal mechanisms and kinetics of trace tetracycline by two types of activated sludge treating freshwater sewage and saline sewage

Understanding the removal mechanisms and kinetics of trace tetracycline by activated sludge is critical to both evaluation of tetracycline elimination in sewage treatment plants and risk assessment/management of tetracycline released to soil environment due to the application of biosolids as fertilizer. Adsorption is found to be the primary removal mechanism while biodegradation, volatilization, and hydrolysis can be ignored in this study. Adsorption kinetics was well described by pseudo-second-order model. Faster adsorption rate (k ₂?=?2.04?×?10^?2?g?min^?1?μg^?1) and greater adsorption capacity (q _e?=?38.8 μg?g^?1) were found in activated sludge treating freshwater sewage. Different adsorption rate and adsorption capacity resulted from chemical properties of sewage matrix rather than activated sludge surface characteristics. The decrease of tetracycline adsorption in saline sewage was mainly due to Mg²⁺ which significantly reduced adsorption distribution coefficient (K _d) from 12,990?±?260 to 4,690?±?180 L?kg^?1. Species-specific adsorption distribution coefficients followed the order of $ K_{\mathrm{d}}^{{ + 00}} \gg K_{\mathrm{d}}^{{ + - 0}} > K_{\mathrm{d}}^{{ + - - }} $ . Contribution of zwitterionic tetracycline to the overall adsorption was >90 % in the actual pH range in aeration tank. Adsorption of tetracycline in a wide range of temperature (10 to 35 °C) followed the Freundlich adsorption isotherm well.     

Studies on the removal of nickel from aqueous solutions using modified riverbed sand

This paper highlights the utility of riverbed sand (RS) for the treatment of Ni(II) from aqueous solutions. For enhancement of removal efficiency, RS was modified by simple methods. Raw and modified sands were characterized by scanning electron microscope (SEM), Energy Dispersive Spectroscopy (EDS), and Fourier Transform Infrared Spectroscopy (FTIR) to investigate the effect of modifying the surface of RS. For optimization of various important process parameters, batch mode experiments were conducted by choosing specific parameters such as pH (4.0–8.0), adsorbent dose (1.0–2.0 g), and metal ion concentrations (5–15 mg/L). Removal efficiency decreased from 68.76 to 54.09 % by increasing the concentration of Ni(II) in solution from 5 to 15 mg/L. Removal was found to be highly dependent on pH of aqueous solutions and maximum removal was achieved at pH 8.0. The process of removal follows first-order kinetics, and the value of rate constant was found to be 0.048 min^?1 at 5 mg/L and 25 °C. Value of intraparticle diffusion rate constant (k _id) was found to be 0.021 mg/g min^1/2 at 25 °C. Removal of Ni(II) decreased by increasing temperature which confirms exothermic nature of this system. For equilibrium studies, adsorption data was analyzed by Freundlich and Langmuir models. Thermodynamic studies for the present process were performed by determining the values of ΔG°, ΔH°, and ΔS°. Negative value of ?H° further confirms the exothermic nature of the removal process. The results of the present investigation indicate that modified riverbed sand (MRS) has high potential for the removal of Ni(II) from aqueous solutions, and resultant data can serve as baseline data for designing treatment plants at industrial scale.     

Removal of arsenic species from water by batch and column operations on bagasse fly ash

Bagasse fly ash (BFA, a sugar industrial waste) was used as low-cost adsorbent for the uptake of arsenate and arsenite species from water. The optimum conditions for the removal of both species of arsenic were as follows: pH 7.0, concentration 50.0 μg/L, contact time 50.0 min, adsorbent dose 3.0 g/L, and temperature 20.0 °C, with 95.0 and 89.5 % removal of arsenate and arsenite, respectively. The Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich adsorption isotherms were used to analyze the results. The results of these models indicated single-layer uniform adsorption on heterogeneous surface. Thermodynamic parameters, i.e., ΔG°, ΔH°, and ΔS°, were also calculated. At 20.0 to 30.0 °C, the values of ΔG° lie in the range of ?4,722.75 to ?4,878.82 and ?4,308.80 to ?4,451.73 while the values of ΔH° and ΔS° were ?149.90 and ?121.07, and 15.61 and 14.29 for arsenate and arsenite, respectively, indicating that adsorption is spontaneous and exothermic. Pseudo-first-order kinetics was followed. In column experiments, the adsorption decreased as the flow rate increased with the maximum removal of 98.9 and 95.6 % for arsenate and arsenite, respectively. The bed depth service time and Yoon and Nelson models were used to analyze the experimental data. The adsorption capacity (N _o) of BFA on column was 3.65 and 2.98 mg/cm³ for arsenate and arsenite, respectively. The developed system for the removal of arsenate and arsenite species is economic, rapid, and capable of working under natural conditions. It may be used for the removal of arsenic species from any contaminated water resources.     

Microwave treatment of dairy manure for resource recovery: Reaction kinetics and energy analysis

A newly designed continuous-flow 915 MHz microwave wastewater treatment system was used to demonstrate the effectiveness of the microwave enhanced advanced oxidation process (MW/H₂O₂-AOP) for treating dairy manure. After the treatment, about 84% of total phosphorus and 45% of total chemical oxygen demand were solubilized with the highest H₂O₂ dosage (0.4% H₂O₂ per %TS). The reaction kinetics of soluble chemical oxygen demand revealed activation energy to be in the range of 5–22 kJ mole^?1. The energy required by the processes was approximately 0.16 kWh per liter of dairy manure heated. A higher H₂O₂ dosage used in the system had a better process performance in terms of solids solubilization, reaction kinetics, and energy consumption. Cost-benefit analysis for a farm-scale MW/H₂O₂-AOP treatment system was also presented. The results obtained from this study would provide the basic knowledge for designing an effective farm-scale dairy manure treatment system.     

Adsorption and desorption variability of four herbicides used in paddy rice production

This investigation was performed to determine the effect of physicochemical soil properties on penoxsulam, molinate, bentazon, and MCPA adsorption–desorption processes. Four soils from Melozal (35° 43′ S; 71° 41′ W), Parral (36° 08′ S; 71° 52′ W), San Carlos (36° 24′ S; 71° 57′ W), and Panimavida (35° 44′ S; 71° 24′ W) were utilized. Herbicide adsorption reached equilibrium after 4 h in all soils. The Freundlich L-type isotherm described the adsorption process, which showed a high affinity between herbicides and sorption sites mainly because of hydrophobic and H-bonds interaction. Penoxsulam showed the highest adsorption coefficients (4.23 ± 0.72 to 10.69 ± 1.58 mL g^?1) and were related to soil pH. Molinate showed K_d values between 1.72 ± 0.01 and 2.3 ± 0.01 mL g^?1and were related to soil pH and organic matter, specifically to the amount of humic substances. Bentazon had a high relationship with pH and humic substances and its K_d values were the lowest, ranging from 0.11 ± 0.01 to 0.42 ± 0.01 mL g^?1. MCPA K_d ranged from 0.14 ± 0.02 to 2.72 ± 0.01 mL g^?1, however its adsorption was related to humic acids and clay content. According to these results, the soil factors that could explain the sorption process of the studied herbicides under paddy rice soil conditions, were principally humic substances and soil pH. Considering the sorption variability observed in this study and the potential risk for groundwater contamination, it is necessary to develop weed rice management strategies that limit use of herbicides that exhibit low soil adsorption in areas with predisposing conditions to soil leaching.     

人工湿地基质对 NH+4-N 吸附性能简

为研究建筑废物红砖和工业废物煤渣用作人工湿地脱氮基质的可行性,分别通过静态吸附实验和动态NH₄⁺-N去除效果实验进行考察。结果表明,红砖和煤渣对NH₄⁺-N最大静态吸附量分别为0.2533 mg/g和0.0533 mg/g,其吸附等温曲线均符合Freundlich型吸附方程,吸附常数分别为0.0419和0.0091;红砖煤渣组合对污水中NH₄⁺-N平均动态脱除率达到41.18%,高于红砖的37.63%和煤渣的30.92%。     

Synthesis of iron composites on nano-pore substrates: Identification and its application to removal of cyanide

Two types of nano-pore substrates, waste-reclaimed (WR) and soil mineral (SM) with the relatively low density, were modified by the reaction with irons (i.e. Fe(II):Fe(III) = 1:2) and the applicability of the modified substrates (i.e. Fe-WR and Fe-SM) on cyanide removal was investigated. Modification (i.e. Fe immobilization on substrate) decreased the BET surface area and PZC of the original substrates while it increased the pore diameter and the cation exchange capacity (CEC) of them. XRD analysis identified that maghemite (γ-Fe₂O₃) and iron silicate composite ((Mg, Fe)SiO₃) existed on Fe-WR, while clinoferrosilite (FeSiO₃) was identified on Fe-SM. Cyanide adsorption showed that WR adsorbed cyanide more favorably than SM. The adsorption ability of both original substrates was enhanced by the modification, which increased the negative charges of the surfaces. Without the pH adjustment, cyanide was removed as much as 97% by the only application of Fe-WR, but the undesirable transfer to hydrogen cyanide was possible because the pH was dropped to around 7.5. With a constant pH of 12, only 54% of cyanide was adsorbed on Fe-WR. On the other hand, the pH was kept as 12 without adjustment in Fe-WR/H₂O₂ system and cyanide was effectively removed by not only adsorption but also the catalytic oxidation. The observed first-order rate constant (k_obs) for cyanide removal were 0.49 (±0.081) h⁻¹. Moreover, the more cyanate production with the modified substrates indicated the iron composites, especially maghemite, on substrates had the catalytic property to increase the reactivity of H₂O₂.     

The Adsorptive Capacity of Vapor-Phase Mercury Chloride onto Powdered Activated Carbon Derived from Waste Tires

Abstract

Injection of powdered activated carbon (PAC) upstream of particulate removal devices (such as electrostatic precipitator and baghouses) has been used effectively to remove hazardous air pollutants, particularly mercury-containing pollutants, emitted from combustors and incinerators. Compared with commercial PACs (CPACs), an alternative PAC derived from waste tires (WPAC) was prepared for this study. The equilibrium adsorptive capacity of mercury chloride (HgCl₂) vapor onto the WPAC was further evaluated with a self-designed bench-scale adsorption column system. The adsorption temperatures investigated in the adsorption column were controlled at 25 and 150 °C. The superficial velocity and residence time of the flow were 0.01 m/sec and 4 sec, respectively. The adsorption column tests were run under nitrogen gas flow. Experimental results showed that WPAC with higher Brunauer–Emmett–Teller (BET) surface area could adsorb more HgCl₂ at room temperature. The equilibrium adsorptive capacity of HgCl₂ for WPAC measured in this study was 1.49 × 10^?1 mg HgCl₂/g PAC at 25 °C with an initial HgCl₂ concentration of 25 μg/m³. With the increase of adsorption temperature ≤150 °C, the equilibrium adsorptive capacity of HgCl₂ for WPAC was decreased to 1.×34 10^?1 mg HgCl₂/g PA≤C. Furthermore,WPAC with higher sulfur contents could adsorb even more HgCl₂ because of the reactions between sulfur and Hg²⁺ at 150 °C. It was demonstrated that the mechanisms for adsorbing HgCl₂ onto WPAC were physical adsorption and chemisorption at 25 and 150 °C, respectively. Experimental results also indicated that the apparent overall driving force model appeared to have the good correlation with correlation coefficients (r) >0.998 for HgCl₂ adsorption at 25 and 150 °C. Moreover, the equilibrium adsorptive capacity of HgCl₂ for virgin WPAC was similar to that for CPAC at 25 °C, whereas it was slightly higher for sulfurized WPAC than for CPAC at 150 °C.