Removal of lead ions from aqueous solutions using powdered corn cobs

This paper is a report on an investigation conducted on adsorption of lead ions (Pb²⁺) onto powdered corn cobs (PCC). Corn cobs were collected from a selected location in Nigeria. The corn cobs were crushed and pulverised into different particle sizes. Its compositions and adsorption properties of Pb²⁺ onto PCC were studied. The effects of pH, particle size of PCC, and initial concentration of Pb²⁺ on the adsorption properties were monitored. The adsorption capacities were analysed by using standard adsorption models. The models were evaluated statistically (total error, coefficient of determination (CD), model of selection criterion (MSC), and root mean square error). The study revealed that PCC contained 2.33%, 86.89%, 10.78%, 0.52%, and 4.56% ash, volatile, moisture, solubility in water, and solubility in 0.25 M of HCl by mass, respectively. Acid digestion of a gram of PCC indicated that PCC contained no chromium and lead, but contained 131 mg Fe, 54.79% carbon, 8.03% hydrogen, 0.41% nitrogen, 0.010 mg of Al, and 1.70 mg calcium. The isotherm models parameters were 28.509 L/mg and 0.141 mg/g; 0.138 mg/g and 11.494 L/mg; 0.142 L/mg and 0.013 mg/g; 0.129 mg/g and 25.641 L/mg, 28.509 L/mg, 3.795 mg/g and 2.336 for Langmuir, Freundlich, Temkin, activated sludge, and Redlich–Peterson. The PCC particle size, initial pH, and initial Pb²⁺ concentration had effects on the adsorption parameters. The statistical evaluations showed that the best model for adsorption of lead ions from raw water onto PCC based on lower errors, high CD (0.88), reliability (97.5%), and MSC (1.86) was Freundlich and followed by activated sludge model. It was concluded that PCC is a good adsorbent like powdered eggshell and other carbon‐based materials.     

菜籽秆预处理废液再生木质素对镉铅离子的吸附性能

采用有机酸法处理菜籽秆并从预处理废液中再生酸不溶性木质素固体,之后对模拟废液中的镉、铅离子进行吸附实验。探讨了木质素再生策略、结晶度、比表面积与基团组成对重金属离子吸附效果的影响。实验结果表明:该类再生木质素能有效地吸附模拟废液中的Cd²⁺、Pb²⁺离子,其功能基团组成是影响吸附效果的关键因素。此外,两种木质素吸附剂吸附Cd²⁺离子的能力均强于吸附Pb²⁺离子的能力。     

Adsorption performance of nickel and cadmium ions onto brewer's yeast

The brewer's yeast was used as adsorbent for the removal of Ni(II) and Cd(II) metal ions from aqueous solution. The surface of the brewer's yeast had three main functional groups of sulfonate, carboxyl, and amine groups. The pH of solution played an important role on the uptake of metal ions, and optimum adsorption was obtained at pH 6. Acid solution (pH 3) was efficient for the desorption of Ni(II) and Cd(II) ions from loaded brewer's yeast and the desorption efficiency was higher than 90%. The rate of metal ions adsorption onto brewer's yeast was rapid with short contact time. The kinetics of the adsorption process was found to follow the pseudo‐second‐order kinetic model. Langmuir and Freundlich isotherm models were used to fit the experimental data with Langmuir isotherm model having a better fit. The maximum uptakes of Ni(II) and Cd(II) by brewer's yeast were estimated to be 5.34 and 10.17 mg/g, respectively.     

Adsorption kinetics of naphthalene onto organo-sepiolite from aqueous solutions

In this study, the adsorption kinetics of naphthalene onto organically modified-sepiolite was investigated by means of the effects of pH, contact time, adsorbent dosage and temperature. The modification of natural sepiolite was accomplished with a cationic surfactant, which is namely dodecyltrimethylammonium (DTMA) bromide. The surface characterization both natural- and modified-sepiolite were carried out by using FTIR method to observe the intercalation of DTMA between the sepiolite layers. The elemental and thermal analyses were also performed to understand the modification. The optimum pH values and the equilibrium contact time for the adsorption of naphthalene onto DTMA–sepiolite were found as 6 and 75 min, respectively. The kinetic parameters of the adsorption process were calculated from experimental data. According to these parameters, adsorption process follows the pseudo-second-order kinetic model with the high correlation coefficients (r² = 0.999). The obtained results show that modified-sepiolite is reasonably effective adsorbent for the removal of organic contaminants, which are an important source for the environmental pollutants.     

木醋液改性羟基磷灰石对溶液中Cd2+的吸附特性

水体中存在Cd²⁺会危害人体健康,Cd²⁺污染的去除是一个需要解决的问题。以羟基磷灰石(HAP)和低成本的木醋液(WV)为原料,通过水浴搅拌制备了木醋液改性羟基磷灰石(WV-HAP),并将其应用于去除溶液中Cd²⁺的研究。利用XRD、FT-IR、SEM、BET对WV-HAP进行了表征,通过吸附试验探究溶液初始pH、初始离子浓度、接触时间和温度对WV-HAP对Cd²⁺吸附特性的影响。结果表明:在吸附剂添加量2 g/L、温度298 K、Cd²⁺初始浓度100 mg/L、pH=5、吸附时间4 h时,WV-HAP的平衡吸附容量为46.43 mg/g;WV-HAP对Cd²⁺的吸附过程符合Langmuir等温吸附模型和准二级动力学模型;热力学研究表明吸附过程是吸热的;通过对吸附Cd²⁺前后的WV-HAP进行表征,发现吸附机制主要是表面吸附、孔道吸附和离子交换。WV-HAP表现出优于HAP的对溶液中Cd²⁺的吸附能力,是一种潜在的Cd²⁺吸附材料。     

Adsorption of cadmium ions from aqueous solutions by activated carbon with oxygen-containing functional groups

The adsorption of aqueous cadmium ions (Cd(II)) have been investigated for modified activated carbon (AC-T) with oxygen-containing functional groups. The oxygen-containing groups of AC-T play an important role in Cd(II) ion adsorption onto AC-T. The modified activated carbon is characterized by scanning electron microscopy, Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The results of batch experiments indicate that the maximal adsorption could be achieved over the broad pH range of 4.5 to 6.5. Adsorption isotherms and kinetic study suggest that the sorption of Cd(II) onto AC-T produces monolayer coverage and that adsorption is controlled by chemical adsorption. And the adsorbent has a good reusability. According to the FT-IR and XPS analyses, electrostatic attraction and cation exchange between Cd(II) and oxygen-containing functional groups on AC-T are dominant mechanisms for Cd(II) adsorption.     

Artificial neural network and multiple linear regression for modeling sorption of Pb2+ ions from aqueous solutions onto modified walnut shell

ABSTRACT

In the present work, for the first time, a new carboxylate-functionalized walnut shell (CFWS) was prepared via esterification of walnut shell (WS) with isopropylidene malonate. The characterization of the CFWS by different techniques approved that carboxylic groups were introduced onto the surface of WS. The performance of the modified adsorbent was studied for the removal of Pb²⁺ ions from aqueous solutions in a batch adsorption system. The analysis data showed that the Langmuir isotherm could satisfactorily explain the equilibrium data, and the maximum adsorption capacity for Pb²⁺ ions was found to be 192.3 mg g^?1 at 0.8 g L^?1 of the adsorbent, pH 5.5, and a temprature of 298 K. Two models, namely artificial neural network (ANN) and multiple linear regression (MLR), were used to construct an empirical model for prediction of the removal percentage of Pb²⁺ ions under different experimental conditions. These models were validated using a test set of 20 data. A comparison between the developed models shows that the ANN model is able to predict the removal percentage of Pb²⁺ ions more accurately. Consequently, the ANN model could be applied for the design of an automated wastewater remediation plan. Also it has to be noted that the used CFWS was recovered using EDTA-2Na, and employed for the removal of Pb²⁺ ions from aqueous solutions.     

Adsorption behaviors and mechanism of heavy metals onto attapulgite functionalized by polyamine silane

Pollution from heavy-metal ions has become a major challenge to the global fight against environmental pollution. Given the availability of various low-cost and environmentally friendly adsorbents, adsorption has become the most efficient technology for the removal of heavy metals from water. In this study, attapulgite (ATP) was directly functionalized by coupling with an aminosilane agent. Analysis showed this maneuver provided a suitable adsorbent for the removal of lead ion (Pb²⁺) from an aqueous solution. The effects of several parameters including solution pH, contacting time, adsorbent dosage, and initial Pb²⁺ ion concentration were investigated. Batch sorption results showed that the adsorption process was rapid and over 98% of Pb²⁺ was removed within 30 min at the optimal pH 4.0. The maximum adsorption capacity at 25°C, calculated by the Langmuir isotherm, was 82.17, 78.80, 61.13, and 28.56 mg/g for γ-divinyltriaminepropyl-methyldimethoxylsilane-grafted attapulgite (KH-103-ATP), γ-aminopropyl-methyldiethoxysilane-grafted attapulgite (KH-912-ATP), N-(β-aminoethyl-γ-aminopropyl)-methyl-dimethoxysilane-grafted attapulgite (KH-602-ATP), and ATP, respectively. Moreover, molecular dynamics simulations of adsorption behaviors of heavy-metal ions at attapulgite surfaces (010) modified by aminosilane agents were carried out. Both the PMF value and diffusion coefficient of metal ions suggest that KH-103-ATP owns the highest rate constant and capacity compared with the other two. And the analysis of free energy and results of XPS characterization revealed that Pb²⁺ formed covalent bonds with the nitrogen atom of aminosilane agents.     

Adsorption equilibrium,kinetics, and dynamic separation of Ca2+ and Mg2+ ions from phosphoric acid-nitric acid aqueous solution by strong acid cation resin

The separation of Ca²⁺ and Mg²⁺ ions from phosphoric acid-nitric acid aqueous solution is very significant for the neutralization process of nitrophosphate fertilizer. This paper studied the adsorption equilibrium, kinetics, and dynamic separation of Ca²⁺ and Mg²⁺ ions by strong acid cation resin, and the effects of phosphoric acid and nitric acid on the adsorption process were investigated. The results reveal that the adsorption process of Ca²⁺ and Mg²⁺ ions in pure water on resin is in good agreement with the Langmuir isotherm model and their maximal adsorption capacities are 1.86 mmol·g^-1 and 1.83 mmol·g^-1, respectively. The adsorption kinetics of Ca²⁺ and Mg²⁺ ions on resin fits better with the pseudo-first-order model, and the adsorption equilibrium in pure water is reached within 10 min contact time, while at the present of phosphoric acid, the adsorption rate of Ca²⁺ and Mg²⁺ ions on resin will go down. The dynamic separation experiments demonstrate that the designed column adsorption is able to undertake the separation of metal ions from the mix acids aqueous solution, but the dynamic operation should control the flow rate of mix acid solution. Besides nitric acid solution was proved to be effective to completely regenerate the spent resin and achieve the recyclable operation of separation process.     

Ca2+ 印迹交联改性壳聚糖的制备及对Cd2+ 的吸附

采用Ca~(2+)印迹保护氨基、戊二醛交联、冻干法造孔、CS2化学改性,制得了Ca~(2+)印迹交联改性壳聚糖(CK)。并用FTIR、XRD和BET对吸附剂的结构进行了表征,通过静态吸附实验考察了其对Cd~(2+)的吸附性能及机理。结果表明:Ca~(2+)保护了氨基;戊二醛与壳聚糖(CS)发生了交联,改善了CS的酸溶性,pH=2时仍可使用;冻干法可使微孔比表面积增大至272.82 m2/g,孔体积增大至0.44 cm3/g;经CS2化学改性,成功引入了C=S基团,提高了CK对Cd~(2+)的吸附性能,平衡吸附量可达49.43 mg/g,比CS的吸附量提高了57.7%。CK对Cd~(2+)的吸附过程符合准二级动力学模型,反应速率常数可达25 g/(g·min);CK对Cd~(2+)的吸附过程符合Freundlich吸附等温式,n值可达4.45;Dubinin Radushkevich模型分析表明:CK吸附Cd~(2+)的平均吸附能为2 236 kJ/mol,是化学吸附;选择性识别实验结果表明:CK对Cd~(2+)具有选择吸附性,除Ca~(2+)外,相对选择性系数均大于3.54。     

酸改性膨润土对含铅废水的吸附性能研究

以硫酸为改性剂,对钙基膨润土进行活化改性,考察了改性剂用量、改性膨润土加入量、吸附时间以及pH值等因素对改性膨润土去除模拟水样中重金属离子Ph^2＋的影响。结果表明,用体积浓度为20％的硫酸溶液改性后的膨润土的除铅效果最好,在常温下,当改性膨润土用量为15g／L,吸附时间为30min,pH值为6-9时废水中铅的去除率最大,超过99.5％,处理后铅的剩余浓度小于1mg/L,达到国家第一类污染物排放标准。     

天然凹凸棒石对水中镉的吸附行为

通过静态实验探讨了天然凹凸捧石吸附水中镉（Cd^2＋）时的影响因素、动力学、等温式和热力学。结果表明,在实验条件下吸附90min后天然凹凸捧石对Cd^2＋的吸附量为6.07-13.15（mg·g^-1）,吸附量随着温度或Cd^2＋初始浓度的增加而增加,但天然凹凸棒石用量增加,吸附量却减少。在pH值为5-7时随着pH值的增加而增加。此外,天然凹凸捧石吸附Cd^2＋的速度较快,吸附60min后基本达到平衡。吸附动力学规律符合Lagergren准二级反应模型,不同温度下的吸附等温式都与Freundlich方程符合很好。热力学分析表明,吸附过程吸热,吸附焓变△H和熵变△s都为正值,吸附自由能变△G为负值。     

膜电解技术处理含铜电镀废水的研究

利用膜电解技术,分别采用硫酸铜、氢氧化钠、草酸和氨水作为阴极膜室电解质对含铜电镀废水进行废水中Cu2+的去除率和回收的实验研究。结果表明:以氨水为电解质,电解4h后,废水中Cu2+的去除率和质量浓度分别为90.72%和10.16mg/L,和其他电解质相比,具有去除效率高、反应时间短等特点。对于废水中Cu2+的回收,由于电解质的不同,回收方式也有差异。     

Adsorption of sulphur dioxide onto activated carbon prepared from oil-palm shells with and without pre-impregnation

Adsorption of sulphur dioxide (SO₂), a common gaseous pollutant, on oil-palm-shell activated carbon in a fixed bed was studied in this paper. Oil-palm shell is an abundant agricultural solid waste in tropical countries like Malaysia and Thailand. The effects of fixed-bed length, SO₂ gas superficial velocity, adsorbent particle size and internal pore structure on fixed-bed performance were investigated. Some characteristic parameters such as the breakthrough time, τ_0.05, exhaustion time, τ_0.95, length of mass transfer zone, L_MTZ, adsorptive capacity, W, and adsorption rate constant, K, were derived from the breakthrough curves. Tests of SO₂ adsorption onto activated carbons prepared from oil-palm shells pre-impregnated with potassium hydroxide (KOH) and phosphoric acid (H₃PO₄) of different concentrations were also carried out. It was found that the fixed-bed performance was not only dependent on the operating conditions and the textural properties of the adsorbent but was also influenced by the surface chemistry of the adsorbent, which was related to the type and concentration of the impregnating agent. In general, the quality of oil-palm-shell activated carbon prepared by CO₂ activation is comparable to that of a commercial product, and the samples prepared from oil-palm shell with KOH pre-impregnation are more suitable for the removal of SO₂ gas.     

基于4-氨基吖啶酮小分子传感器的设计、合成及识别性能研究

基于以往的研究进一步设计合成了一种Cu2小分子传感器4-((3-甲氧基-.4-羟基苄亚基)氨基)吖啶-9(10H)-酮(4-AAVS).该化合物结构经1HNMR、13CNMR和HR-MS确认.通过紫外-可见光谱法和荧光光谱法研究4-AAVS在水溶液中对金属离子的识别能力.实验结果表明,在pH 6.24～8.0的水溶液体系中,该化合物对Cu2表现出优良的选择性识别作用.利用荧光滴定实验可得,该化合物和Cu2的配位比为2∶1,离子浓度在0.1～0.4×10-6 mol/L时,线性相关系数R=0.988 89,最低检出限为1.8×10-9 mol/L.     

盐离子对蒙脱石水化膨胀特性的影响

采用热失重法与经离心法、直接烘干法、冷冻干燥法结合对蒙脱石样品水含量进行测量,分析了NaCl浓度对蒙脱石中结合水与自由水含量的影响,探讨了蒙脱石中总含水量及结合水含量随NaCl溶液浓度变化的规律,研究了NaCl溶液中蒙脱石的水化膨胀特性及盐离子的抑制作用。结果表明,蒙脱石的水化膨胀受盐离子的抑制,盐离子的存在减小了渗透水化力,影响了水分子间的范德华力及水分子和蒙脱石表面间的氢键力和静电引力,总含水量随盐离子浓度增加而降低,盐离子浓度为0.2 mol/L时趋近最低值,样品膨胀程度由6.6缩小至1.6,盐离子对蒙脱石水化膨胀的抑制作用达峰值。盐离子浓度大于0.2 mol/L时,随盐离子浓度增加,自由水与结合水含量变化不明显。     

离子交换水软化技术研究与应用进展

离子交换法是目前最常见的水软化技术之一,其基于可逆的离子交换反应将溶液中的硬度离子选择性去除,属于典型的特种分离过程。本文介绍并总结了离子交换水软化的基本原理、水软化用离子交换树脂的结构和分类、离子交换水软化技术研究和应用,并针对离子交换水软化存在的问题提出了相应的解决思路。     

一种巯基胺型羧酸螯合树脂的制备及其吸附性能

以环硫氯丙烷和多乙烯多胺为原料,通过交联反应合成了巯基胺型树脂(PA树脂)。然后对PA树脂进行氯乙酸化反应,合成了巯基胺型羧酸螯合树脂(PAC树脂),并通过傅立叶变换红外光谱仪(FTIR)对其结构进行了表征。研究了PAC树脂对模拟含Cu2+电镀废水的吸附性能,探讨了树脂用量、吸附时间和pH对Cu2+吸附性能的影响。实验结果表明,在常温常压下,取25 mL浓度为10 mmol/L的废水溶液,PAC树脂吸附Cu2+的最佳用量为0.40 g/mmol Cu2+,最佳吸附时间为150 min,最佳pH为6~10,最大吸附量和最大吸附率分别达到2.53mmol/g和94.7%。PAC树脂对Cu2+的吸附过程符合Langmiur和Freundlich等温吸附方程。     

8-羟基喹啉型吸附材料对重金属离子的吸附研究

以多孔型无机材料Si O2作载体,通过偶联剂γ-氨丙基三甲氧基硅烷的媒介作用,将5-氯甲基-8羟基喹啉(CHQ)分子接枝到硅胶表面,制备新型复合型螯合吸附材料CHQ-AMPS/Si O2。研究了接枝微粒CHQ-AMPS/Si O2对废水中重金属离子Pb2+和Ni2+的吸附行为,考察了接枝微粒CHQ-AMPS/Si O2对Pb2+和Ni2+的吸附动力学曲线和等温线,研究了温度和p H对接枝微粒CHQ-AMPS/Si O2吸附Pb2+和Ni2+的影响和其可再生性能。结果发现微粒CHQ-AMPS/Si O2对于Pb2+和Ni2+的吸附最适温度分别是35℃,25℃;最适p H分别是7和6。