Removal of copper ions by a cation-exchange resin in a semifluidized bed

The removal of copper ions was studied experimentally in a semifluidized bed charged with a strong cation-exchange resin, Amberlite 200C. The semifluidized bed system was formed by inserting a retaining grid in a packed bed and increasing the fluid velocity above U_mf. In this arrangement, the bed is separated into two sections; the upper packed bed section and the lower fluidized bed section. As the fluid velocity increases, the portion of the packed bed section becomes larger. As expected, the breakthrough curve obtained from the semifluidized bed lies between those from packed and fluidized beds. The breakthrough curves of copper ions were predicted reasonably well by using an axial dispersion model. In this paper, the effects of the liquid flowrate and the retaining grid height on the breakthrough behavior are extensively discussed.     

Continuous biosorption of heavy metal ions by Ca-loadedlaminaria japonica in fixed bed column

Continuous biosorption process for removal of lead and copper by laboratory scale fixed-bed reactor was carried out using Ca-loadedLaminaria japonica. All biosorption processes were observed as cation exchange such as Pb²⁺ vs. Ca²⁺, Cu²⁺ vs. Ca²⁺, and Pb²⁺ vs. Cu²⁺. The affinity of lead ions towardsL. japonica was stronger than that of copper ions because the initial amount of desorbed Cu²⁺ in Cu-Pb system was higher than that of eluted Pb²⁺ in Pb-Cu system.     

Simultaneous removal of cyanide and copper ions in a semi-fluidized ion exchanger bed

Simultaneous removal of cyanide and copper ions from electroplating wastewater was studied in a liquid-solid semi-fluidized ion exchanger bed. The diameter and the height of column are 20 mm and 600 mm, respectively. Strong-base anion exchange resin particles (Dowex 1X8-50) were contacted with synthetic solutions containing copper and cyanide ions. Cyanide and copper ions in the solution were analyzed by a cyanide electrode and ICP (inductively coupled plasma), respectively. The ion exchange equilibrium data of Cu⁺ removed as cyanide-copper complexes on Dowex 1X8-50 at 25 ‡C can be fitted with the Langmuir equation. Early leakage of cyanide from experimental loading profile data results in not only lower selectivity of free cyanide but also different selectivities of CN-Cu complexes due to the size and the structure of complexes. The optimum molar ratio (Q) between cyanide and copper ions is about 3 to obtain a reasonable removal rate of cyanide in this experiment.     

Simultaneous removal and recovery of cadmium and cyanide ions in synthetic wastewater by ion exchange

Simultaneous removal and recovery of cyanide and cadmium ions using a strong-base anion exchange resin was studied on the basis of formation of Cd-CN complexes at high pH in synthetic wastewater containing cyanide and cadmium ions. Strong-base anion exchange resin particles, of Dowex1X8-50, were contacted with synthetic aqueous solutions. For different molar ratios between cyanide and cadmium, ion exchange characteristics of cadmium-cyanide complexes were studied experimentally in a batch reactor. Treatment efficiencies of packed and fluidized beds were compared under various conditions. Several regenerants, NaSCN, NaCN, and NaOH, were used to regenerate the exhausted resin. The rates of regeneration and recovery for the various regenerants were estimated and discussed. The resin used in this work, Dowex1X8-50, can exchange about 6.6 CIST meq./g resin and 3.2 Cd²⁺ meq./g resin of cyanide and cadmium ions as complexes, respectively. Free cyanide ion has a lower selectivity than Cd-CN complexes on the anion exchange resin. The degree of treatment efficiency applied in this study was greater in the fluidized bed than packed bed. NaSCN was the best regenerant among regenerants used for regeneration of resin saturated with Cd-CN complexes.     

Removal of heavy metal ions with water-insoluble amphoteric sodium tertiary amine sulfonate starches

The removal of heavy metal ions (Pb⁺², Cu⁺² and Zn⁺²) from solutions with high crosslinked amphoteric starch containing the sulfonate anionic group and the tertiary ammonium cationic group was investigated. The adsorption capacity of sodium tertiary amine sulfunate starch is 0.050 meq/g. The adsorption process has been found to be concentration and pH dependent and exothermic, and follows the Langmuir isothermal adsorption. The heat of adsorption (H) of Pb⁺², Cu⁺² and zn⁺² ions is equal to –10.85. –16.20 and –20.00 Kcal/mole, respectively. The amount of adsorbed metal ions on the adsorbent decreases when NaCl or Na₂SO₄ is added to the solution.     

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。     

Application of insoluble cellulose xanthate for the removal of heavy metals from aqueous solution

Insoluble cellulose xanthate (ICX), O-alkyl dithiocarbonate of cellulose, was synthesized and used for the removal of heavy metal ions from aqueous solutions. ICX possessed carbon disulfide (CS₂) as a functional group, which was obtained by esterification of the hydroxyl group on cellulose polymer matrix with CS₂. CS₂ could form complexes with divalent transition metal ions, and the resulting ICX-metal complex was water-insoluble and settled easily. The optimum composition for ICX synthesis was cellulose/NaOH/CS₂=1: 2: 2.3 in mole base, which showed the highest removal capacity. The selectivity and binding capacity of ICX for heavy metals were in the order of Pb²⁺> Cd²⁺> Ni²⁺ and Cd²⁺> Pb²⁺> Ni²⁺, respectively. More than 90 % of the initial amount of heavy metals was removed within 30 min. The optimum pH was neutral or slightly alkaline, and more than 40 % of initial heavy metals was removed even in the acidic range of pH 2 to 3.     

Removal of contaminants from aqueous solutions by beds made of rejects of the lightweight aggregates production

This work describes the attempt to reuse rejected sieved fractions from the lightweight expanded clay aggregates production, as filter bed, used in the removal of some water contaminants, namely nickel, lead and suspended particles, as an alternative to land filling deposition.     

Removal of Congo Red dye from aqueous solution using Amberlite IRA-400 in batch and fixed bed reactors

Removal of Congo Red (CR) azo dye by adsorption process using Amberlite IRA-400 resin was evaluated in both batch and fixed bed system. From the batch adsorption results, maximum loading efficiency (99.99%) of CR dye was obtained at the conditions pH 4.5, temp. 303?K, contact time 180?min., Amberlite IRA-400 dose 0.5?g. The isotherm study ascertained on favorability of adsorption process as the value of separation factor (K_L?=?0.88) and Freundlich constant (1/n?=?0.96?R²?=?0.99) than Freundlich model (R²?=?0.97). The kinetic data studied at three different CR dye concentration (50, 75, 100?mg) and results were fitted with both pseudo-first-order and second-order model equations. The values of R² obtained are of 0.95 and 0.99 for former and later one, respectively, ensuring on best fitting of pseudo-second-order kinetics and also suggesting about the chemisorptions type of adsorption. The bed depth service model was applied for competitive analysis of the CR dye adsorption in column variables indicating mass transfer from aqueous solution to Amberlite IRA-400 phase. Fourier transform infrared analysis of CR-loaded resin Amberlite IRA-400 showed a band shifted from 1057 to 1130?cm^?1 confirming CR adsorption with Amberlite IRA-400. Scanning electron microscope analysis of resin before and after adsorption was well evident from the phase patterns. Selective separation of CR dye from waste effluent of a textile industry bearing CR dye along with other trace heavy metal was achieved.     

丙烯酰胺-丙烯酸-丙烯羟肟酸共聚物乳液脱除电镀废水中的重金属离子

采用反相乳液聚合法合成了丙烯酰胺(AM)-丙烯酸(AA)- 丙烯羟肟酸(AHA)共聚物乳液。考察了该共聚物配方中丙烯羟肟酸用量、共聚物乳液的投量和pH值对电镀废水中重金属离子的脱除效果。结果表明：pH=10,丙烯羟肟酸在共聚物乳液中的用量≥15%,共聚物乳液的投量为20～30 mg/L时,脱除电镀废水中重金属离子的效果最好,Cr、Cu、Ni和Zn等重金属离子的脱去率≥99.5%,处理后的水中每种重金属离子浓度≤0.2 mg/L。     

Removal of heavy metal ions by dithiocarbamate-anchored polymer/organosmectite composites

In this study, the dithiocarbamate-anchored polymer/organosmectite composites were prepared for the removal of heavy metal ions (lead, cadmium and chromium) from aqueous media containing different amounts of these ions (50–750 ppm) and at different pH values (2.0–8.0). Initially, the modification of the natural smectite minerals was performed by treatment with quartamin styrene and chloromethylstyrene. Then, modified smectite nanocomposites were reacted with carbondisulfide, in order to incorporate dithiocarbamate functional groups into the nanolayer of organoclay. The dithiocarbamate-anchored nano-composites have been characterized by FTIR and used in the adsorption–desorption process. The maximum adsorptions of heavy metal ions onto the dithiocarbamate-anchored polymer/organosmectite composites from their solution was 170.7 mg g^− 1 for Pb(II); 82.2 mg g^− 1 for Cd(II) and 71.1 mg g^− 1 for Cr(III). Competition between heavy metal ions (in the case of adsorption from mixture) yielded adsorption capacities of 70.4 mg g^− 1 for Pb(II); 31.8 mg g^− 1 for Cd(II) and 20.3 mg g^− 1 for Cr(III). Desorption of the heavy metal ions from composite was studied in 0.5 M NaCl and very high desorption rates, greater than 93%, were achieved in all cases. Adsorption–desorption cycles showed the feasibility of repeated uses of this nanocomposite.     

Air oxidation of aqueous cyanides in a countercurrent fixed bed reactor

This study was conducted to discuss the removal of cyanides from water by air oxidation. Experiments were carried out in a countercurrent fixed bed reactor for three different values of temperature, concentration, gas and liquid flow rates. It was operated at pH 12 by using delrin (formaldehyde polymer) as packing material. Effects of some operating parameters on the conversion were studied, and it was observed that the conversion percent increased by increasing temperature and decreasing gas and liquid flow rates. Effect of concentration was not steady. A conversion of 89% was achieved under optimum conditions while it ranges from 44 to 79% at room temperature.     

Adsorption of some heavy metal ions from aqueous solutions on Nafion 117 membrane

Nafion 117 membrane was investigated for the removal of Ni(II), Co(II), Pb(II), Cu(II) and Ag(I) metal ions from their synthesized aqueous solutions. The different variables affecting the adsorption capacity of the membrane such as contact time, initial metal ion concentration in the feed solution, pH of the sorption medium and temperature of the solution were investigated on a batch sorption basis. The affinity of Nafion 117 membrane towards heavy metal ions was found to increase in the sequence of Cu(II), Ni(II), Co(II), Pb(II), and Ag(I) with adsorption equilibrium achieved after 30 min for all metal ions. Among all parameters, pH has the most significant effect on the adsorption capacity, particularly in the range of 3.1-5.9. The variation of temperature in the range of 25-65 °C was found to have no significant effect on the adsorption capacity. Nafion 117 membrane was found to have high stability combined with repeated regeneration ability and can be suggested for effective removal of heavy metal ions such as Cu(II), Ni(II) and Co(II) from aqueous solutions.     

Gasification characteristics of combustible wastes in a 5 ton/day fixed bed gasifier

The gasification characteristics of combustible wastes were determined in a 5 ton/day fixed bed gasifier (1.2 m I.D. and 2.8m high). The fixed bed gasifier consisted of air compressor, oxygen tank, MFC, fixed bed gasifier, cyclone, heat exchanger, solid/gas separator, water fluidized bed reactor and blower. To capture soot or unburned carbon from the gasification reaction, solid/gas separator and water fluidized bed were used. The experiments with 10–50 hours of operation were carried out to determine the effects of bed temperature, solid/oxygen ratio and oxidant on the gas composition, calorific value and carbon conversion. The calorific values of the produced gas decreased with an increase of bed temperature because combustion reaction happened more actively. The gas composition of partial oxidation of woodchip is CO: 34.4%, H₂: 10.7%, CH₄: 6.0%, CO₂: 48.9% and that of RPF is CO: 33.9%, H₂: 26.1%, CH₄: 10.7%, CO₂: 29.2%. The average calorific values of produced gas were about 1,933 kcal/Nm³, 2,863 kcal/Nm³, respectively. The maximum calorific values were 3,100 kcal/Nm³ at RPF/oxygen ratio: 7     

Adsorption capacity and removal efficiency of heavy metal ions by Moso and Ma bamboo activated carbons

In order to understand the adsorption capacity and removal efficiency of heavy metal ions by Moso and Ma bamboo activated carbons, the carbon yield, specific surface area, micropore area, zeta potential, and the effects of pH value, soaking time and dosage of bamboo activated carbon were investigated in this study. In comparison with once-activated bamboo carbons, lower carbon yields, larger specific surface area and micropore volume were found for the twice-activated bamboo carbons. The optimum pH values for adsorption capacity and removal efficiency of heavy metal ions were 5.81–7.86 and 7.10–9.82 by Moso and Ma bamboo activated carbons, respectively. The optimum soaking time was 2–4 h for Pb²⁺, 4–8 h for Cu²⁺ and Cd²⁺, and 4 h for Cr³⁺ by Moso bamboo activated carbons, and 1 h for the tested heavy metal ions by Ma bamboo activated carbons. The adsorption capacity and removal efficiency of heavy metal ions of the various bamboo activated carbons decreased in the order: twice-activated Ma bamboo carbons > once-activated Ma bamboo carbons > twice-activated Moso bamboo carbons > once-activated Moso bamboo carbons. The Ma bamboo activated carbons had a lower zeta potential and effectively attracted positively charged metal ions. The removal efficiency of heavy metal ions by the various bamboo activated carbons decreased in the order: Pb²⁺ > Cu²⁺ > Cr³⁺ > Cd²⁺.     

Removal of zinc ions in wastewater by electrodialysis

To obtain useful data for treatment of the wastewater discharged from zinc electroplating processes, we investigated the effects of operating parameters, such as the initial concentration of dilute solution, the flow velocity and the applied voltage, on removal rate of Zn²⁺ in the model solutions using an electrodialysis system. Zinc ions in the solutions were effectively removed by the electrodialyzer with CMX cation exchange membranes and AMX anion exchange membranes. The initial concentration of dilute solution, the flow velocity and the applied voltage strongly affected the performance of the electrodialysis system. As the initial concentration of dilute solution, the flow velocity and the applied voltage were increased, the removal ratio was increased. The energy consumption was increased as the initial concentration of dilute solution and the applied voltage were increased, whereas the effect of the flow velocity on the energy consumption was negligible.     

Preparation of porous and hollow Mn2O3 microspheres and their adsorption studies on heavy metal ions from aqueous solutions

Mn₂O₃ microspheres are prepared and used as adsorbent for removal of heavy metal ions. Morphology and structure of Mn₂O₃ microspheres are analyzed by SEM, TEM, XRD, XPS and N₂ sorption technique. Effects of adsorbent concentration, ion concentration and agitation time on adsorption behavior are investigated. Adsorption isotherm and kinetics are also studied. The results show Mn₂O₃ microspheres have well-developed porous and hollow structure, demonstrating good potential on removal of heavy metal ions. Adsorption data fit better with Freundlich isotherms than Langmuir isotherms. Kinetic studies indicate adsorption behavior is described by pseudo-second-order kinetic model, and intra-particle diffusion plays a significant role.     

Hydrogenation of CO2 over Fe-K based catalysts in a fixed bed reactors at elevated pressure

Catalytic hydrogenation of CO₂to produce hydrocarbons was conducted in a fixed bed reactor (1.6 cm-IDx60 cm-High). Fe-K based catalysts (KRICAT-A, B) were used for more than 850 hours to maintain CO₂ conversion level up to 30 C-mol% in the fixed bed micro-reactor. Effects of operating variables on the CO₂ conversion, hydrocarbon yield and its selectivity were investigated. The CO₂ conversion and total hydrocarbon yield increased with increasing reaction temperature (250-325 °C), pressure (0.5-2.5 MPa) and H₂/CO₂ mol ratio (2-5); however, they decreased with increasing space velocity (1,000-4,000 ml/g_cathr) in the reactor. The selectivities of liquid products increased with increasing reaction pressure; however, they decreased with increasing temperature, space velocity and H₂/CO₂ ratio. From the results of an experimental study, optimum operating conditions for the maximum yield of olefinic liquid products were found as T=315 °C, P=1.5 MPa, SV=2,000 ml/g_cathr and H₂/CO₂ ratio=3 in the fixed bed reactor within these experimental conditions. Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his retirement from Korea University.     

Removal of metal ions in aqueous solutions by organic polymers: use of a polydiphenylamine resin

Adsorption of Ni(II), Cu(II), Zn(II), Pb(II) and Cd(II) ions on a polydiphenylamine resin prepared at a strongly oxidizing controlled potential of 3.2 V (vs. ECS) was studied in aqueous solutions. The optimum sorption conditions were determined. The optimum pH for the removal of metal ions was between 4 and 6 for Ni(II), 6 for Cu(II) and Pb(II) and 5 for Zn(II) and Cd(II). The total sorption capacity of the resin was 57.3 mg g⁻¹ for Ni(II), 23 mg g⁻¹ for Cu(II), 36.9 mg g⁻¹ for Zn(II), 19 mg g⁻¹ for Pb(II) and 24.5 mg g⁻¹ for Cd(II). The sorption capacity was compared with other conventional chelating polymers. The sorption kinetics was fairly rapid, as apparent from the loading half time (t_1/2) values, indicating a better accessibility of the chelating sites. The study of the selectivity of the metal ions in the binary solutions shows that the resin presents a higher affinity for the ions of nickel (II).     

Adsorption of surfactants from water onto raw and HCl-activated clays in fixed beds

The removal of surfactants from water by adsorption onto raw and HCl-activated montmorillonite in fixed beds was studied. Three surfactants hexadecylpyridinium chloride (cationic), sodium dodecyl sulfate (anionic), and Triton X-102 (non-ionic) were selected in the concentration ranges lower than their critical micelle concentrations in fixed bed experiments. It was shown that the adsorption of anionic surfactant onto Ca-montmorillonite (SAz-1) decreased with increasing pH but that of cationic surfactant increased. The adsorption capacity of non-ionic surfactant was maximized at pH 7.0. For given clay, the adsorption capacities of surfactants were strongly pH-dependent. The adsorption capacity and adsorption rate of non-ionic surfactant onto SAz-1 could be largely improved after acid activation of the clay. Such an improvement was due to the fact that the dissolution of Al³⁺ or Fe²⁺ of montmorillonite occurs in acid solution. The calculated breakthrough curves in fixed bed agreed with the measured ones (standard deviation < 6%). The 50% C/C₀ breakthrough time (τ) decreased with increasing liquid flow rate. The effects of flow rate on the adsorption constant and adsorption capacity were also discussed.