A study of removal of Pb heavy metal ions from aqueous solution using lignite and a new cheap adsorbent (lignite washing plant tailings)

The present study determines the efficiency with which lignite and lignite washing plant tailings can adsorb Pb heavy metal ions. In the first experiment, the effect of size distribution on the absorbance capacity was investigated for the samples. Therefore, lignite sample was ground to five sizes (d₈₀ = 0.600, 0.355, 0.250, 0.106 and 0.063 mm) under nitrogen (N₂), and the tailings sample was classified into seven fractions, along with the original state (original state: d₆₀ = 0.063, −1 + 0.600, −0.600 + 0.355, −0.355 + 0.250, −0.250 + 0.106, −0.106 + 0.063 and −0.063 mm). The test results showed that the optimum size distributions for lignite and tailings were d₈₀ = 0.063 mm and the original state (d₆₀ = 0.063 mm), respectively. Simultaneously, the adsorption capacity results of the two optimum sizes were compared with each other, and the tailings sample (d₆₀ = 0.063 mm) gave the best results, with 9.30 mg/g Pb ions adsorbed value. Therefore, in the second study, a series of laboratory experiments using 2³ full factorial designs was conducted to determine the optimum pH, contact time and initial metal concentration using the original tailings sample. The experimental studies showed that pH 9, a 120 min contact time and 300 ppm initial metal concentration gave the best results, namely an adsorption of 29.92 mg Pb ions/g.     

Removal of heavy metal ions from aqueous solution by multi-walled carbon nanotubes modified with 8-hydroxyquinoline: Kinetic study

Carbon nanotubes were modified with 8-hydroxyquinoline and used for the removal of Cu(II), Pb(II), Cd(II), and Zn(II) from aqueous solutions. Different instrumentation parameters and methods of development for determining metal ions from aqueous solutions using differential pulse anodic stripping voltammetry were studied. The adsorption of heavy metals from aqueous solution by the pristine and modified MWCNTs was studied kinetically using different kinetic models, and the results showed that the adsorption process best fitted the pseudo-second-order model and the Elovich model. The mechanism of adsorption was explored using the intra-particle diffusion model and the liquid-film model.     

Removal of metal ions from electrochemical decontamination solution using organic acids

Applicability of the organic acids and cyclodextrin (CD) for the removal of Fe, Co and Ni from the spent electro-decontamination solution was investigated. Oxalic acid showed the highest removal efficiency: 90% for 0.89 M Fe and 95% for 0.0089 M Co and Ni, respectively. The metal–oxalate precipitates were characterized by differential scanning calorimetry/thermogravimetry analysis (DSC/TGA), Fourier transform infrared (FTIR) and X-ray fluorescence (XRF). After thermal decomposition at >300°C, the metal–oxalate precipitates were transformed into metal oxides (Fe₂O₃, FeO, CoO and NiO) and pure metals (Co and Ni). The results imply that organic acids have a high potential for the removal of heavy metals from electro-decontamination solutions.     

Removal of heavy metals from water by lignite-based sorbents

Calcium-loaded lignite was used to remove heavy metals from wastewater by ion exchange. The following quantities were determined experimentally: calcium-loading capacity for different types of lignite, selectivity coefficients of Cu, Zn, Pb, Cd, Ni, Co and Fe(II) ions, kinetic sorption dependences and the effect of flow rate on the shape of break-through curves in column experiments. Sorption kinetics was relatively slow and consequently, the sorption dynamics was influenced by this phenomenon. A numerical code taking into account the sorption kinetics was used for modelling, which proved its applicability for scaled-up columns.The process is very efficient especially in the case of low concentrations of pollutants in water, where common methods are either economically unfavourable or technically complicated. This is very often the case of various metals in the environment, and thus the method could be convenient for their removal.     

Removal of Cd(II) and Cu(II) from aqueous solutions using mesoporous silicate containing zirconium and iron

The present work elucidates an environmental friend by process for heavy metals removal from aqueous solutions using mesoporous silicate, containing zirconium and iron. The process comprises the three following steps: (1) synthesis and characterization of mesoporous silicate bed (the prepared adsorbent materials were characterized by powder X-ray diffraction, nitrogen isotherms, FTIR, TGA, and SEM). (2) Evaluation of the efficiency of this new adsorption bed for Cu and Cd removal from aqueous solutions. (3) Study of metal concentration (50-1000 ppm), stirring time (0.5-5 h) and pH (1.5-12) effects on the adsorption power using batch techniques. Results obtained indicate that under optimum conditions, pH in the vicinity of 5-6, Zr-M has the maximum adsorption capacity for both cations Cu and Cd. On the other hand, ZrFe-M1 containing a higher molar ratio of iron showed lower adsorption capacity for the cations Cu and Cd.     

Synthesis of a carbamide-based dithiocarbamate chelator for the removal of heavy metal ions from aqueous solutions

This study was carried out to develop a carbamide-based dithiocarbamate (CDTC) chelator for the removal of heavy metal ions from wastewater. Its structural properties were characterized by FT-IR, ¹H NMR and ¹³C NMR. Results confirmed the functional groups of HNC(S)S existed. The adsorption isotherms showed CDTC had a high adsorption capability for Zn (119.8 mg/g) and Cu (63.1 mg/g). It exhibited a distinctive selectivity for the removal of metal ions (Cu²⁺ > Zn²⁺ > Cr³⁺ > Pb²⁺ > Cd²⁺) as they coexisted. The influence of initial pH of wastewater for the removal efficiency of metal ions was also investigated and a pH > 7 was preferred.     

Minimization of organic chemical load in direct dyes effluent using low cost adsorbents

The work is carried out to minimize the organic chemical load (unexhausted dye contents) in direct dyes effluent using low cost adsorbents. The studies are made with different direct dyes, i.e. Direct Red 28, Direct Yellow 12, Direct Orange 26 and Direct Blue 1 with various adsorbents. Three different bio/natural materials have been selected as adsorbents. These includes, Sugarcane bagasse pith (SB), Saw dust (SD)—the plant origin products, and Brick powder (BP)—a silica based material obtained from earth's crust on thermal heating. These substances are almost discarded waste products with the possibility of use as adsorbents. Experimental work for the dye removal from the effluent by activated charcoal (AC) has also been carried out and the results are compared with other adsorbents. The amount of unexhausted organic dye present in the effluent is measured as chemical oxygen demand (COD) before and after the treatment. Adsorbent Sugarcane bagasse pith shows good performance as compared to Saw dust and Brick powder. For understanding the behaviour of adsorbents Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) has also been carried out.     

重金属离子脱除技术进展

综述了脱除水中重金属离子的各类主要方法 ,侧重介绍了近年来开发的若干新技术。     

Removal of strontium ions from aqueous solution using hybrid membranes: Kinetics and thermodynamics

The removal of radionuclide from radioactive wastewater has captured much attention. Strontium-90 is one of the major radionuclides. To develop a new type of adsorbents to remove strontium ions from the radioactive wastewater, in this study, novel hybrid membranes were prepared and characterized. The adsorption kinetics, thermodynamic parameters of ΔG, ΔH and ΔS, as well as surface SEM and EDS images were used to investigate the removal of strontium ions from stimulated radioactive wastewater using the previously prepared hybrid membranes as efficient adsorbents. The study of kinetic model confirmed that the adsorption of strontium ions on these hybrid membranes followed the Lagergren pseudo-second order model. Moreover, it was proved that the adsorption of strontium ions on these samples was solely controlled by intraparticle diffusion. The negative values of ΔG and the positive values of ΔH indicated that the adsorption of strontium ions on samples A-D is a spontaneous and endothermic process in nature. Furthermore, surface SEM and DES images give significant evidence to confirm the existence of strontiumions on the surface of the adsorbed samples. These findings demonstrate that these hybrid membranes are promising adsorbents for the removal of strontium ions from aqueous solution and can be potentially applied in the adsorptive separation of radionuclides from the radioactive wastewater.     

Removal of metal ions from aqueous solution by adsorption onto activated carbon cloths: adsorption competition with organic matter

Activated carbon cloths are recent adsorbents whose adsorption properties are well known for monocomponent solutions of organics or metal ions. However, to treat wastewaters with these materials, their performance has to be determined in multicomponent solution. This work studies adsorption competition between metal ions (Cu²⁺, Pb²⁺) and organic matter (benzoic acid). The first part investigates adsorption equilibrium of monocomponent metal ions solutions and shows the dependence of adsorption capacities on adsorbent porosity and metal ions chemical properties (molecular weight, ionic radius and electronegativity). The influence of pH is also demonstrated. The second part focuses on adsorption competition: (1) between both metal ions (a decrease of adsorption capacities is observed, whose value is related to adsorption kinetics of metal ions); (2) between metal ions and organic matter, in solution or adsorbed onto the activated carbon cloth (a strong influence of pH is shown: when benzoic acid is under benzoate form, in both cases adsorption is increased due to the formation of ligands between adsorbed benzoate ions and metals).     

Polyvinyl Alcohol/Alginate/Zeolite Nanohybrid for Removal of Metals

A novel polyvinyl alcohol/alginate/zeolite nanohybrid adsorbent for the adsorption of Ni(II) and Co(II) metal ions was prepared by the casting method. The prepared adsorbent was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy as well as Barrett-Joyner-Halenda and Brunauer-Emmett-Teller analyses. The optimum adsorption conditions in terms of content of zeolite nanoparticles, adsorbent dosage, and initial pH were determined. The kinetic data for both ions were well described by the double-exponential kinetic model. The obtained Langmuir maximum adsorption capacities of Ni(II) and Co(II) metal ions were 81.51 and 79.58 mg g⁻¹, respectively. The adsorption/desorption experiments showed a good performance after 5 cycles of adsorption.     

Adsorption of Pb2+ on Chitosan Cross‐Linked with Triethylene‐Tetramine

A novel triethylene‐tetramine cross‐linked chitosan (CCTS) was synthesized via the cross‐linking of triethylene‐tetramine and epichlorohydrin activated chitosan. Its structure was characterized by elemental analysis, infrared spectroscopy and X‐ray diffraction analysis, and the surface topography was determined with ESEM. The results were in agreement with expectations. The capacity of CCTS to adsorb Pb²⁺ ions from aqueous solutions was examined, and equilibrium and kinetic investigations were undertaken. The adsorption isotherms were fitted well by the Langmuir equation (R > 0.999). The maximum adsorbed amount, at pH 5.5, with an initial concentration of 3 mmol/L (621 ppm), was 378.8 mg/g. The adsorption process could be best described by a second‐order equation (R = 1). This suggests that the rate‐limiting step may be the chemical adsorption (chemisorption) step and not the mass transport. The separation factor used was 0 < R_L < 1. Therefore, it can be concluded that CCTS is an effective adsorbent for the collection of Pb²⁺.     

Modelling of heavy metal adsorption into activated carbon from apricot stones in fluidized bed

The purpose of the present study is to investigate the behaviour of activated carbon from apricot stones (ACAS) in a closed circuit fluidized bed (CCFB) for removal of Pb, Cu, Cd and Zn ions from aqueous solution. The expansion characteristics of the bed are studied. A homogeneous solid phase diffusion model was used to describe the mass transfer inside the adsorbent particles. A piston-dispersion model was applied for the liquid phase in the bed and compared to the calculations, assuming perfect mixing conditions in the whole CCFB adsorber. The close correspondence between the experimentally determined adsorption in batch and fluidized bed operation modes support the observation that the CCFB can be described by a stirred batch adsorption model. The concentration profile at the bed exit is satisfactorily predicted by the model, thus confirming the equilibrium and kinetic parameters, determined from the laboratory batch adsorption runs.     

Equilibrium and kinetic studies on the removal of some metal ions using biogenic amorphous silica

In the present study agricultural waste (rice husks) was used for the production of biogenic silica. The resulting material was obtained by incineration of rice husks at a temperature of 800°С and was characterized by means of XRD, FTIR, SEM-EDS, Hg-porosimetry and N₂-adsorption. The adsorption ability of the rice husks ash towards Fe(III), Pb(II), Cr(III) and Cu(II) ions in single- and multi-component aqueous solutions was studied in a batch system. The effects of contact time, acidity of initial solutions and metal ion concentrations were followed. Different models were used to determine the adsorption mechanism. Equilibrium experimental data were fitted to linear Langmuir and Freundlich models. The maximum adsorption capacities for single- and multi-component adsorption were calculated.     

Study of heavy metal removal from heavy metal mixture using the CCD method

The central composite design (CCD) technique was used to study the effect of the native species Lemna gibba on the removal heavy metals from the mixture of heavy metals, and understand their impact on the process. The effects of Cd, Cr, Cu, Zn, and Ni cations, incubation period and fronds number on heavy metals removal (Cd, Cr, Cu, Zn, and Ni) were studied, and the results were statistically analyzed using JMP 9.0.2 (SAS Institute) software. The analysis aimed at giving a mathematical model that shows the influence of each variable. Each factor has a distinct effect on heavy metal removal. High correlation was found between the experimental and predicted results, reflected by R² (coefficient of determination).     

Removal of several metal ions from aqueous solution using powdered stem of Arundo donax L. as a new biosorbent

Arundo donax L., a member of Poaceae, was washed, dried, selected, pulverized, and then used for removal of Cu(II), Cd(II), Ni(II), Pb(II) and Zn(II) from aqueous solution. Series batch experiments were conducted to investigate the effects of contact time, pretreatment, particle size of biomass and solution pH on the biosorption capability of A. donax L. powder. The desorption characteristics and renewability of the biomass were also studied. The applicability of Langmuir and Freundlich isotherms was examined for the experimental data, so did the pseudo-first-order, pseudo-second-order and Elovich kinetic models. Results showed that alkali-treated A. donax L. biomass was more appropriate to be the bio-material for biosorption when compared to acid-treated, washed and virgin A. donax L. Owing to its fast adsorption rate, high uptake capacity and the renewability of facility, stem of A. donax L. treated with NaOH seems to be a promising biosorbent for removal of heavy metals from wastewater.     

Adsorption of Cd(II), Hg(II) and Zn(II) from aqueous solution using mesoporous activated carbon produced from Bambusa vulgaris striata

Mesoporous activated carbon (surface area of 608 m²/g) has achieved high efficiency in removal of cadmium, mercury and zinc ions from water solution. The proposed low-cost adsorbent was physically activated with water steam from the bamboo species Bambusa vulgaris striata. The batch studies suggested an activated carbon dose of 0.6 g/L, solution pH of 9 and an equilibrium time of 16 h in static conditions. The pseudo-second order equations represented the adsorption kinetics with high correlation. Fitting of the experimental results to the Langmuir, Freundlich, Redlich–Peterson and Toth isotherm models showed an almost homogeneous surface coverage and presence of physical adsorption. The highest adsorption capacities, calculated from the Langmuir model, are 239.45, 248.05 and 254.39 mg/g of cadmium, mercury and zinc, respectively.     

用酵母菌吸附处理废水中重金属离子研究现状

酵母菌作为一种生物吸附剂,廉价易得,对重金属、低pH及其它外界条件有较强的耐受度.利用酵母菌,特别是固定化酵母菌吸附废水中的重金属离子,不仅成本低、去除率高、再生能力强,而且对吸附的重金属易于回收.随着相关技术的发展,酵母菌吸附剂必将在废水处理中得到更广泛的应用.