Optimization of ammonia removal by ion-exchange resin using response surface methodology

The ability of ion-exchange resin for ammonia removal from aqueous solution was studied. The results showed that Amberlite ion-exchange resin was effective in removing ammonia from aqueous solution. Factorial design and response surface methodology were applied to evaluate and optimize the effects of pH, resin dose, contact time, temperature and initial ammonia concentration. Low pH condition was preferred with the optimum pH found to be 6. High resin dose generated high removal rate and low exchange capacity. Results of factorial design and response surface methodology showed that temperature was not a significant parameter. The model prediction was in good agreement with observed data (R ² = 0.957). The optimum Q _e was 28.78 mg/g achieved at pH = 6 and initial TAN concentration of 3000 mg/L. The kinetics followed the pseudo-second-order kinetic model (R ² = 0.999). Equilibrium data were fitted to Langmuir and Freundlich isotherm models with Langmuir model providing a slightly better predication (R ² = 0.996). The resin was completely regenerated by 2 N H₂SO₄.     

铀试剂螯合形成树脂分离富集极谱连测样品的贵金属元素

采用2-邻胂酸偶氮苯-1, 8-二羟基-3, 6-二磺酸钠(铀试剂) 作为螯合剂制备螯合形成树脂, 并研究了该树脂的性能及对分离富集和测定结果的影响因素。实验发现, 用pH = 1.0的盐酸溶液做淋洗剂、柱高为8 cm、流速为1.00 mL /min、pH = 1.0的3%的硫脲-盐酸40 mL洗脱时, 贵金属离子能和常见的金属离子分离, 定量富集于树脂上。用极谱法测定贵金属元素的标准回收实验表明, 其回收率为94% ～106%。     

Sorption of metals on humic acid

The sorption on humic acid (HA) of metals from an aqueous solution containing Hg(II). Fe(III), Pb, Cu, Al, Ni, Cr(III), Cd, Zn, Co and Mn, was investigated with special emphasis on effects of pH, metal concentration and HA concentration. The sorption efficiency tended to increase with rise in pH, decrease in metal concentration and increase in HA concentration of the equilibrating solution. At pH 2.4. the order of sorption was: Hg? Fe? Pb? CuAl ? Ni ? CrZnCdCoMn. At pH 3.7. the order was: Hg and Fe were always most readily removed, while Co and Mn were sorbed least readily. There were indications of competition for active sites (CO₂H and phenolic OH groups) on the HA between the different metals. We were unable to find correlations between the affinities of the eleven metals to sorb on HA and their atomic weights, atomic numbers, valencies, and crystal and hydrated ionic radii. The sorption of the eleven metals on the HA could be described by the equation $\text{Y =}\text{100}\text{[1 + exp ? (A + BX)]}$, where Y = % metal removed by HA; X = mgHA; and A and B are empirical constants.     

从含镍废触媒中回收镍的工艺实验

合镍废触媒原料经H2S04二次浸取，调节PH值，加沉淀剂除铁、重金属、铝等杂质，蒸发结晶，生产硫酸镍，产品质量达到国家一类标准，镍的总回收率达到92．3％。     

Aqueous heavy metals removal by adsorption on β-diketone-functionalized styrene–divinylbenzene copolymeric resin

An investigation was undertaken regarding the adsorption of different heavy metal ions from aqueous solutions using ??-diketone-functionalized styrene divinylbenzene resin under different experimental conditions such as initial concentration of metal ions, contact time, pH, and chelating capacity. The functionalization of resin was carried out by the condensation reaction of sodium salt of ??-diketones (pentane-1,3-dione) and chloromethylated styrene?Cdivinylbenzene resin in dichloromethane. Functionalized resin beads were characterized by Fourier transform infrared spectroscopy. The batch method was employed using different metal ions solution from 5 to 15?mg/L at different contact times. The adsorption kinetics was tested for the pseudo-first order, pseudo-second order reaction at different experimental conditions. The rate constant of adsorption kinetic models were also calculated and good correlation coefficient (R ²?>?0.9941) was obtained for pseudo-second order kinetic model. The maximum adsorption value obtain for lead (0.725728?mg/g), chromium (0.9199?mg/g), nickel (0.4974?mg/g), cobalt (0.6196?mg/g) and cadmium (0.6519?mg/g) at equilibrium condition, which shows that ??-diketone-functionalized styrene divinylbenzene resin is an effective adsorbent for toxic metal ions.     

Sorption and distribution of adsorbed metals in three soils of India

The mobility and bioavailability of heavy metals depends on the metal retention capacity of soil and also on the geochemical phases with which metals are associated. Laboratory batch experiments were carried out to study the sorption and distribution of Cd, Ni and Pb in 3 soils differing in their physicochemical properties from India: Oxyaquic Haplustalf (SL1), Typic Haplustalf (SL2) and Typic Haplustert (SL3). The heavy metal adsorption was studied by isotherms and the distribution coefficient (K_D) for each metal was obtained from the linear regressions of the concentration of metal remaining in equilibrium solution and the amount adsorbed. In general, the sorption capacity for all the metals decreased in the order: SL3>SL2>SL1. Among metals, the sorption capacity in all the soils decreased in the order: Pb>>Ni>Cd. Distribution of sorbed metals at various equilibrating concentrations was studied by sequential extraction. Results showed significant differences in the distribution of metals in these soils. At higher additions (such as 200 μM l⁻¹) most of the metals were extracted in their more mobile fractions, exchangeable and/or inorganic in contrast to their original partitioning in soils, where they were preferentially associated with the less mobile residual fraction. Largest percentages of metals extracted in the exchangeable fraction corresponded to those soil–metal systems with smaller K_D values, e.g. Cd, Ni and Pb in SL1 and Cd and Ni in SL2. In neutral and alkaline soils (SL2, pH=7.1, and SL3, pH=8.6) Pb was predominantly extracted from the inorganic fractions and this corresponded to higher K_D values for Pb in these soils. The predominance of metals associated with the exchangeable fraction together with low K_D values indicates higher mobility of metals retained in the acidic soil (SL1, pH=5.2) compared with the others.     

Geochemical reactions and dynamics during titration of a contaminated groundwater with high uranium, aluminum, and calcium

This study investigated possible geochemical reactions during titration of a contaminated groundwater with a low pH but high concentrations of aluminum, calcium, magnesium, manganese, and trace contaminant metals/radionuclides such as uranium, technetium, nickel, and cobalt. Both Na-carbonate and hydroxide were used as titrants, and a geochemical equilibrium reaction path model was employed to predict aqueous species and mineral precipitation during titration. Although the model appeared to be adequate to describe the concentration profiles of some metal cations, solution pH, and mineral precipitates, it failed to describe the concentrations of U during titration and its precipitation. Most U (as uranyl, UO₂²⁺) as well as Tc (as pertechnetate, TcO₄⁻) were found to be sorbed and coprecipitated with amorphous Al and Fe oxyhydroxides at pH below ∼5.5, but slow desorption or dissolution of U and Tc occurred at higher pH values when Na₂CO₃ was used as the titrant. In general, the precipitation of major cationic species followed the order of Fe(OH)₃ and/or FeCo_0.1(OH)_3.2, Al₄(OH)₁₀SO₄, MnCO₃, CaCO₃, conversion of Al₄(OH)₁₀SO₄ to Al(OH)_3,am, Mn(OH)₂, Mg(OH)₂, MgCO₃, and Ca(OH)₂. The formation of mixed or double hydroxide phases of Ni and Co with Al and Fe oxyhydroxides was thought to be responsible for the removal of Ni and Co in solution. Results of this study indicate that, although the hydrolysis and precipitation of a single cation are known, complex reactions such as sorption/desorption, coprecipitation of mixed mineral phases, and their dissolution could occur simultaneously. These processes as well as the kinetic constraints must be considered in the design of the remediation strategies and modeling to better predict the activities of various metal species and solid precipitates during pre- and post-groundwater treatment practices.     

Adsorption of heavy metals in glacial till soil

The charged sites on soil particles are important for the retention/adsorption of metals. Metallic counterions can neutralize the intrinsic charges on the surfaces of soil particles by forming complexes. In this study, efforts have been made to determine the effect of surface potential, pH, and ionic strength on the adsorption of four metal ions, hexavalent chromium Cr(VI), trivalent chromium Cr(III), nickel Ni(II) and cadmium Cd(II), in glacial till soil. Batch tests were performed to determine the effect of pH (2–12) and ionic strength (0.001–0.1 M KCl) on zeta potential of the glacial till soil. The point of zero charge (pH _PZC ) of glacial till was found to be 7.0±2.5. Surface charge experiments revealed the high buffering capacity of the glacial till. Batch adsorption experiments were conducted at natural pH (8.2) using various concentrations of selected metals. The adsorption data was described by the Freundlich adsorption model. Overall glacial till shows lower adsorption affinity to Cr(VI) as compared to cationic metals, Cr(III), Ni(II) and Cd(II).     

Origin of nickel in water solution of the chalk aquifer in the north of France and influence of geochemical factors

In the north of France, high registers of nickel are sometimes recorded within the chalk aquifer. In a confined context, the presence of pyrite in the covering clays or in the marcasite nodules encrusted in the clay may constitute a natural source of trace metals. With an objective of sanitary control, the limits of chemical contents regulating the quality of water destined for human consumption have been lowered by the European Framework Directive in the field of water policy (2000/60/EC). As a result, nickel limits have been reduced from 50 to 20 μg/l. The analyses, carried out on three water catchment fields in our area of study, were centred on variable parameters (Eh, O₂(d), pH, Conductivity, T°), major elements (SO₄, NO₃) and metals (Fe, Ni, Mn, Co). The acquired data enabled us to identify from one hand, the conditions which are presented within the site, special thanks to the evolution of nitrate and iron contents and on the other hand, the natural origin (geological) of nickel for two of the three sites studied based essentially on the evaluation of the Nickel/Cobalt ratio. Thus, on the first site, the evolution of nickel content and nitrate content showed the influence of the phenomenon of denitrification on the re-mobilisation of the nickel. Whereas on the second site, a high variation of total iron content and oxygen dissolved in solution highlighted a particular phenomenon of oxidation of the pyrite through molecular oxygen. Finally, the correlation with the sulphates clearly showed behaviour of the nickel, once released, that was entirely dependent on the phenomenon of adsorption on the iron and manganese hydroxides.     

Towards finding an efficient sorbent for antimony: comparative investigations on antimony removal properties of potential antimony sorbents

Removal of antimony, classified as a pollutant of priority importance, is a challenge due to its presence in various forms in solution and the low concentration in which it is to be removed. In this study, sorption profile and the sorption mechanisms associated with the removal of antimony in its two oxidation states (+3 and +5) have been investigated in detail through batch studies involving titania sorbents, strong base anion resin, a chelating resin, and a biosorbent. Significant sorption-associated change in solution pH was observed with all the sorbents, which revealed the nature of respective sorption equilibrium involved. The results have shown that Sb(V) is removed only as anionic species, while Sb(III) is removed either as an anionic species or as cationic species according to the functional groups present in the sorbent and the solution conditions. Titania-based sorbents were found to be effective sorbents for Sb(III) and Sb(V) within a narrow pH range, while anion resin was found to be superior for removing Sb(V) as Sb(OH) ₆ ^? under a wide range of solution conditions. The suitability of the sorbents for column mode of operation has also been investigated. This report is a first attempt at a rational comparison of promising sorbents for antimony, and the results demonstrate the complexity involved in antimony sorption and give an understanding of the available options for handling the antimony removal problem in large-scale applications.     

Dynamic fuzzy neural network for simulating the fixed-bed adsorption of cadmium,nickel, and zinc on bone char

This study introduces the application of a dynamic fuzzy neural network for fitting and simulating the adsorption of nickel, cadmium, and zinc ions in mono- and bi-metallic solutions (nickel–cadmium, nickel–zinc, and cadmium–zinc) using packed-bed columns with bone char. This neural network model has shown a flexible and self-adaptive architecture with a faster learning speed than that of traditional artificial neural approaches. Results showed that this neural network model was reliable for representing the high asymmetry behavior of concentration profiles in both mono- and bi-metallic breakthrough curves where its accuracy was quite reasonable. Breakthrough parameters for mono-component and binary systems of tested heavy metals were calculated and compared. This analysis showed that the removal of these heavy metal ions in binary systems was a strong competitive adsorption process where the presence of co-ions reduced the removal performance of bone char at fixed-bed adsorbers. Results of surface characterization of adsorbent samples with X-ray photoelectron and infrared spectroscopy supported a removal mechanism based on an ion exchange between calcium from hydroxyapatite of bone char and heavy metal ions in the solution forming new metal–phosphate interactions in the adsorbent surface.     

Experimental study of the stability of metals associated with iron oxyhydroxides precipitated in acid mine drainage

Iron oxyhydroxide precipitates associated with acid mine drainage (AMD) from the Stearns Coal Zone in southeastern Kentucky were analyzed for their metal (Al, Cu, Pb, Mn, Ni, and Zn) content. The most concentrated metals within these sediments are nickel (27–32×10³μmol/kg), manganese (16–29×10³μmol/kg), and aluminum (13–22×10³μmol/kg) as determined by HCl-HNO₃ digestion. Metal concentrations associated with the organic fraction as determined by H₂O₂ digestion were generally far lower, with the exception of aluminum. "Batch" experiments (at initial pH=2.0) were used to analyze the stability of these metals associated with a contaminated soil. Aluminum was the most mobile of the metals, presumably the result of the formation of aluminum-sulfate aqueous complexes. The solubilization rates for nickel and iron were very similar, suggesting that nickel, unlike the other metals, coprecipitated with iron in these sulfatic oxyhydroxides. Received: 9 October 1997 · Accepted: 15 December 1997     

New chelating resin for preconcentration and determination of molybdenum by inductive couple plasma atomic emission spectroscopy

A chelating resin is prepared by condensation polymerization of aniline with formaldehyde and characterized by Fourier transform infrared spectrometer, elemental analysis and thermogravimetric analysis and studied for the preconcentration and determination of trace Molybdate ion from environmental water sample using inductive couple plasma atomic emission spectroscopy. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 3.1 mg/g. The chelating sorbent can be reused for 20 cycles of sorption-desorption without any significant change in sorption capacity. The best desorption of the metal ions from resin was obtained by 0.5 mol/L nitric acid as eluting agent. The profile of molybdenum uptake on this sorbent reflects good accessibility of the chelating sites in the aniline-formaldehyde. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Molybdate ion modified resin were analyzed by five isotherm models such as Langmuir, Freundlich and Temkin. Langmuir isotherm parameters obtained from the four Langmuir linear equations by using linear method. Based on the Langmuir isotherm analysis, the monolayer adsorption capacity was determined to be 4.03 mg/g at 20 °C. The method was applied for molybdenum ions determination from river water sample.     

An optimized procedure for boron separation and mass spectrometry analysis for river samples

An optimized procedure for the separation of boron from natural river samples and an improved mass spectrometry determination of boron isotopic ratio are presented. The chemical procedure, based on the use of the boron-specific resin Amberlite IRA 743, is especially efficient in separating boron from natural organic matter-rich samples like river waters.The properties of Amberlite IRA 743 have been investigated. The two factors important in determining the boron affinity for the resin are: the pH value and the ionic strength of the solution from which B is to be extracted. A logarithmic relationship between B partition coefficients and pH values is found. High ionic strength significantly lowers the fixation of B onto the Amberlite resin.The knowledge of the factors controlling the affinity of the resin Amberlite IRA 743 for boron enables us to design a simple and miniaturized chemical separation procedure characterized by (i) three chromatographic steps using, respectively, 50, 10 and 3 μl of resin, (ii) no evaporation step between each column, and (iii) final separation of boron from residual organic matter by sublimation of boric acid at 75 °C.Boron isotopic ratios are measured using an improved cesium metaborate technique, with graphite and mannitol. Adequate loading conditions enable us to obtain typical signal intensities of 5×10⁻¹² A for 250 ng of boron. No in-run isotopic fractionation is observed, the external reproducibility for standards processed through the entire chemical procedure, as well as for samples, corresponds to 0.35‰ (±2σ). According to this precision, a slight, but reproducible isotopic fractionation of 0.4‰ is observed for standards processed through the entire chemical procedure whose origin is discussed, but is still unclear.     

凹凸棒石与Ni2+的长期吸附作用

以Ni2+为例研究了凹凸棒石与重金属离子长期作用过程,探讨了重金属离子在凹凸棒石上的吸附反应动力学,并运用高分辨透射电镜揭示了凹凸棒石与重金属离子互相作用引起重金属离子水解沉淀、形成氢氧化物或层状双氢氧化物次生物相的现象.实验表明,凹凸棒石-Ni2+水悬浮体系中,随着时间的延长溶液的pH值逐渐升高,Ni2+浓度逐渐降低,并且长期作用后悬浮液的pH值和重金属离子浓度受到固/液比控制.Ni2+在凹凸棒石和水两相中的分配在长达40 d的时间内都没有达到完全平衡,表明凹凸棒石-Ni2+水悬浮体系中存在凹凸棒石与重金属离子长期互相作用.凹凸棒石与Ni2+长期作用Ni2+浓度变化可以用抛物线扩散方程、双常数方程、一级扩散方程、Elovich方程较好地拟合.凹凸棒石与重金属的长期作用反应机制可能是由于凹凸棒石纳米效应和反应活性,表面缓慢水化导致含重金属离子溶液pH值缓慢升高,诱导了Ni2+在凹凸棒石表面沉淀,在凹凸棒石表面形成了氢氧化物或层状双氢氧化物.     

Kinetic and equilibrium study of Ni(II) sorption from aqueous solutions onto Peganum harmala-L

In this study, the adsorption behavior of Ni(II) in an aqueous solution system using natural adsorbent Peganum harmala-L was measured via batch mode. The prepared sorbent was characterized by scanning electron microscope, Fourier transform infrared spectroscopy, N₂ adsorption–desorption and pH_zpc. Adsorption experiments were carried out by varying several conditions such as contact time, metal ion concentration and pH to assess kinetic and equilibrium parameters. The equilibrium data were analyzed based on the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherms. Kinetic data were analyzed using the pseudo-first-order, pseudo-second-order and intra-particular diffusion models. Experimental data showed that at contact time 60 min, metal ion concentration 50 mg/L and pH 6, a maximum amount of Ni(II) ions can be removed. The experimental data were best described by the Langmuir isotherm model as is evident from the high R ² value of 0.988. The adsorption capacity (q _m) obtained was 68.02 mg/g at an initial pH of 6 and a temperature of 25 °C. Kinetic studies of the adsorption showed that equilibrium was reached within 60 min of contact and the adsorption process followed the pseudo-first-order model. The obtained results show that P. harmala-L can be used as an effective and a natural low-cost adsorbent for the removal of Ni(II) from aqueous solutions.     

Reclamation of EDTA by sodium tetraethylenepentamine-multi dithiocarbamate after soil washing process with EDTA

Ethylenediaminetetraaceticacid (EDTA) has been proven to be an efficient soil washing liquid to remove metal contaminants from soils. However, EDTA may cause secondary pollution due to its low biodegradability if it is not recycled or destroyed in the washing process. Thus, it is necessary to recycle and recover EDTA for sustainable use. In this paper, the extracting performance of fresh EDTA was firstly studied as a function of EDTA concentration, liquid/sediment (L/S) ratio and pH of the solution, and also extraction time. Then sodium tetraethylenepentamine-multi dithiocarbamate (TEPA-DTC), a heavy metals capturing agent, was synthesized on the base of the research of LIU-Lihua. Compared with Na₂S and DDTC, TEPA-DTC shows strong chelating capacity, because it has functional groups of dithiocarbamate that could strongly chelate heavy metals and capture metal ions from Me-EDTA to form precipitates, allowing us to reclaim the EDTA during the process of soil washing. Three divalent heavy metals were investigated (Pb, Cd, and Cu). These three metals could almost precipitate completely with TEPA-DTC under the dosage of 300 mg/l, and EDTA was regenerated. The recovered EDTA was used again in three cycles of soil washing, and the amount of heavy metals extracted just slightly decreased each cycle.     

ZH型重金属螯合纤维对水溶液中Sr2+的吸附行为

研究了ZH型重金属螯合纤维对水溶液中Sr~(2+)的吸附行为,考察了pH值、纤维加入量、Sr~(2+)初始浓度、作用时间等对吸附行为的影响,并采用SEM、EDS和FTIR等现代分析测试手段探讨了ZH型重金属螯合纤维对Sr~(2+)的吸附机制。结果表明,在pH值为7.0、纤维加入量为2.0 g/L、Sr~(2+)初始质量浓度为50 mg/L的条件下,纤维对Sr~(2+)的吸附在4 h左右基本达到平衡。实验条件下ZH型重金属螯合纤维对Sr~(2+)的最大吸附量可达26.22 mg/g。等温吸附拟合结果表明,ZH型重金属螯合纤维对Sr~(2+)的吸附可能是以单分子层为主的单分子层和多分子层吸附共同作用的结果。纤维对Sr~(2+)的动力学吸附过程符合准二级动力学模型。红外光谱分析表明Sr~(2+)与纤维上—NH_2和—COOH等基团进行配位络合从而吸附在纤维表面,—CH_2—和C=CH_2等基团参与此吸附过程。能谱分析表明Sr~(2+)与纤维上Na~+和Ca~(2+)还存在着离子交换作用。     

Heavy metals removal from synthetic wastewater by a novel nano-size composite adsorbent

The effects of varying operating conditions on metals removal from aqueous solution using a novel nano-size composite adsorbent are reported in this paper. Characterization of the composite adsorbent material showed successful production of carbon nanotubes on granular activated carbon using 1 % nickel as catalyst. In the laboratory adsorption experiment, initial mixed metals concentration of 2.0 mg/L Cu²⁺, 1.5 mg/L Pb²⁺ and 0.8 mg/L Ni²⁺ were synthesized based on metals concentration from samples collected from a semiconductor industry effluent. The effects of operation conditions on metals removal using composite adsorbent were investigated. Experimental conditions resulting in optimal metals adsorption were observed at pH 5, 1 g/L dosage and 60 min contact time. It was noted that the percentage of metals removal at the equilibrium condition varied for each metal, with lead recording 99 %, copper 61 % and nickel 20 %, giving metal affinity trend of Pb²⁺ > Cu²⁺ > Ni²⁺ on the adsorbent. Langmuir’s adsorption isotherm model gave a higher R² value of 0.93, 0.89 and 0.986 for copper, nickel and lead, respectively, over that of Freundlich model during the adsorption process of the three metals in matrix solution.     

Study of mango biomass (Mangifera indica L) as a cationic biosorbent

Unfertilizable fruiting buds of mango plant Mangifera Indica L, an agrowaste, is used as a biomass in this study. The efficacy of the biosorbent was tested for the removal of lead, copper, zinc and nickel metal ions using batch experiments in single and binary metal solution under controlled experimental conditions. It is found that metal sorption increases when the equilibrium metal concentration rises. At highest experimental solution concentration used (150 mg/L), the removal of metal ions were 82.76 % for lead, 76.60 % for copper, 63.35 % for zinc and 59.35 % for nickel while at lowest experimental solution concentration (25 mg/L), the removal of metal ions were 92.00% for lead, 86.84 % for copper, 83.96 % for zinc and 82.29 % for nickel. Biosorption equilibrium isotherms were plotted for metal uptake capacity (q) against residual metal concentrations (C_f) in solution. The q versus C_f sorption isotherm relationship was mathematically expressed by Langmuir and Freundlich models. The values of separation factor were between zero and one indicating favourable sorption for four tested metals on the biosorbent. The surface coverage values were approaching unity with increasing solution concentration indicating effectiveness of biosorbent under investigation. The non-living biomass of Mangifera indica L present comparable biosorption capacity for lead, copper, zinc and nickel metal ions with other types of biosorbent materials found in literature and is effective to remove metal ions from single metal solutions as well as in the presence of other co-ions with the main metal of solution.