Copper and cadmium removal from synthetic industrial wastewater using chitosan and nylon 6

Purpose

Chitosan with nylon 6 membranes was evaluated as adsorbents to remove copper and cadmium ions from synthetic industrial wastewater.

Methods

Chitosan and nylon 6 with glutaraldehyde blend ratio with (1:1+Glu, 1:2+Glu, and 2:1+Glu) have been prepared and these were used as membranes to remove copper and cadmium ions from synthetic industrial wastewater. Characterization of the synthesized membrane has been done with FTIR, XRD, TGA/DTA, DSC, and SEM. Chemical parameters for quantities of adsorption of heavy metal contamination have been done and the kinetics of adsorption has also been carried out.

Results

The optimal pH for the removal of Cd(II) and Cu(II) using chitosan with nylon 6. Maximum removal of the metals was observed at pH 5 for both the metals. The effect of adsorbent dose also has a pronounced effect on the percentage of removal of the metals. Maximum removal of both the metals was observed at 5 g/100 ml of the adsorbent.

Conclusion

Copper and cadmium recovery is parallel at all time. The percentage of removal of copper increased with increase in the pH from 3 to 5. In the case of cadmium containing wastewater, the maximum removal of metal occurred at pH 5. The uptake amount of Cu²⁺ ions on chitosan increased rapidly with increasing contact time from 0 to 360 min and then reaches equilibrium after 360 min; the equilibrium constant for copper and cadmium ions is more or less the same for the adsorption reaction.     

An electrogenerative process for the recovery of gold from cyanide solutions

Traditional methods for the recovery of gold from electronic scrap by hydrometallurgy were cyanidation followed by adsorption on activated carbon or cementation onto zinc dust and by electrowinning. In our studies, a static batch electrochemical reactor operating in an electrogenerative mode was used in gold recovery from cyanide solutions. A spontaneous chemical reaction will take place in the reactor and generate an external flow of current. In this present work, a static batch cell with an improved design using three-dimensional cathodes namely porous graphite and reticulated vitreous carbon (RVC) and two-dimensional cathode materials, copper and stainless steel plates were coupled with a zinc anode. The electrogenerative system was demonstrated and the performance of the system using various cathode materials for gold recovery was evaluated. The system resulted in more than 90% gold being recovered within 3h of operation. Activated RVC serves as a superior cathode material having the highest recovery rate with more than 99% of gold being recovered in 1h of operation. The morphology of gold deposits on various cathode materials was also investigated.     

Influence of clay on the adsorption of heavy metals like copper and cadmium on chitosan

The influence of clay on the adsorption of heavy metals like copper and cadmium on chitosan from simulated industrial wastewater is evaluated. Chitosan–clay blend with ratio of (1:1), (1:2), and (2:1) have been prepared, and these were used as membranes to remove copper and cadmium ions from synthetic industrial wastewater. The chemical parameters for quantities of adsorption of heavy metal contamination have been done, and the kinetics of adsorption has also been carried out. Clay provides enough absorbable sites to overcome mass transfer limitations. The number of absorbable sites for cadmium is more compared to copper, and thus the rate of recovery of cadmium is faster than copper, and the percentage removal of cadmium is more than copper at all times on clay over nylon 6. This difference indicates the influence of clay in the adsorption of heavy metals in comparison to synthetic polymer nylon 6. Rate constant for first-order kinetics of adsorption, k ₁, for copper and cadmium is less than that of clay, which clearly indicates that clay, which is a natural polymer, is more kinetically favored compared to synthetic polymer. The difference in the intraparticle diffusion in both the natural and synthetic polymer is not much, and it suggests that the particle diffusion mechanism is the same in both cases. Copper and cadmium recovery is parallel at all times. The percentage of removal of copper increased with an increase in pH from 3 to 5. In the case of cadmium containing wastewater, the maximum removal of metal occurred at pH 5. The uptake amount of Cu²⁺ ions on chitosan increased rapidly with increasing the contact time from 0 to 360 min and then reaches equilibrium after 360 min, and the equilibrium constant for copper and cadmium ions are more or less the same for the adsorption reaction. There are more adsorption sites for cadmium in the presence of clay and mass transfer limitation is avoided without resorting to rotation, which is the highlight of the present work. And more so, this is pronounced in the case of natural polymer compared to synthetic polymer.     

Pilot-plant study of wastewater sludge decontamination using a ferrous sulfate bioleaching process.

The objective of this research was to investigate the performance of the ferrous sulfate bioleaching (FSBL) process in a pilot plant for decontamination and stabilization of wastewater sludge. Batch and continuous experiments, conducted with two 4-m3 bioreactors using indigenous iron-oxidizing bacteria (20% v/v of inoculum) with addition of 4.0 g ferrous sulfate heptahydrate per liter of sludge initially acidified to pH 4.0, were sufficient for effective heavy metal (cadmium, copper, manganese, zinc, and lead) removal yields. The average metal removal yields during the FSBL process were as follows: cadmium (69 to 75%), copper (68 to 70%), manganese (72 to 73%), zinc (65 to 66%), and lead (16%). The FSBL process was also found to be effective in removing both fecal and total coliforms (abatement > 5 to 6 log units). The nutrients content (nitrogen, phosphorus, and magnesium) were also preserved in decontaminated sludge.     

Investigation of heavy metal accumulation in Polygonum thunbergii for phytoextraction

In this study, cadmium (II), lead (II), copper (II) and zinc (II) were determined in Polygonum thunbergii and soil from the Mankyung River watershed, Korea. Soil samples contained detectable lead (<17.5 g g(-1)), copper (<8.4 g g(-1)) and zinc (<24.5 g g(-1)), whereas cadmium was undetectable. Whole plants of P. thunbergii contained detectable lead (<320.8 g g(-1)), copper (<863.2 g g(-1)) and zinc (<2427.3 g g(-1)), whereas cadmium was detectable only in the stem (<7.4 g g(-1)) and root (<10.1 g g(-1)). Whole plant concentrations were very different for each metal, particularly in the case of zinc. The mean content of heavy metal in the whole plants increased in the order of cadmium (8.5 g g(-1))相似文献   

Heavy metal removal from synthetic wastewaters in an anaerobic bioreactor using stillage from ethanol distilleries as a carbon source

This work was conducted to investigate the possibility of using stillage from ethanol distilleries as substrate for sulfate reducing bacteria (SRB) growth and to evaluate the removal efficiency of heavy metals present in wastewaters containing sulfates. The experiments were carried out in a continuous bench-scale Upflow Anaerobic Sludge Blanket reactor (13 l) operated with a hydraulic retention time of 18 h. The bioreactor was inoculated with 7 l of anaerobic sludge. Afterwards, an enrichment procedure to increase SRB numbers was started. After this, cadmium and zinc were added to the synthetic wastewater, and their removal as metal sulfide was evaluated. The synthetic wastewater used represented the drainage from a dam of a metallurgical industry to which a carbon source (stillage) was added. The results showed that high percentages of removal (>99%) of Cd and Zn were attained in the bioreactor, and that the removal as sulfide precipitates was not the only form of metal removal occurring in the bioreactor environment.     

可渗透反应复合电极法对土壤重金属的电动去除

将零价铁(Fe0)、沸石等活性材料附着在电极上形成可渗透反应层并构成可渗透反应复合电极,采用不同的复合电极对Cd2+、Ni 2+、Pb2+和Cu2+等4种阳离子型重金属污染土壤进行了电动力学修复。研究了不同可渗透反应复合电极对土壤pH的控制效果以及对重金属的去除作用,分析了迁移到复合电极中的重金属形态变化。结果表明,复合电极中添加酸、碱性沸石并适时更换,可有效中和、截留阴阳极电解产生的OH-和H+,避免或减缓土壤酸碱迁移带的形成,防止重金属离子的过早沉淀及土壤过度酸化,极大提高了重金属的去除率。复合电极中Fe0可将迁移进来的重金属离子进行还原稳定,实现重金属污染物的捕获与固定,与迁移到沸石复合电极中的4种重金属不稳定态相比,"Fe0+沸石"复合电极中重金属不稳定态分别下降了61.4、60.5、61.4、57.1百分点。结果还显示,阴极采用"Fe0+沸石"复合电极并适时进行更换,施加1.5V/cm的直流电压修复10d后,土壤中Cd、Ni、Pb、Cu的总去除率分别为44.5%、41.5%、33.5%和36.7%,且进一步延长修复时间和持续更换电极可获得更为理想的修复效果。     

浮游球衣菌对Pb2+、Cu2+、Zn2+、Cd2+的吸附性能研究

研究了浮游球衣菌（Sphaerotilus natans）在不同吸附条件下对溶液中Pb^2＋、Cu^2＋、Zn^2＋、Cd^2＋的吸附规律。结果表明,Sphaerotilus natans对这4种重金属离子均有一定的吸附作用,并在20min内达到吸附平衡,pH对吸附过程影响较大,pH为5.5时Sphaerotilus natans对这4种金属离子的吸附效果最好,Sphaerotilus natans对它们的吸附选择性为Pb^2＋〉Cu^2＋〉Zn^2＋〉Cd^2＋,Pb^2＋、Cu^2＋能部分置换出已被菌体吸附的Zn^2＋、Cd^2＋。HCI和EDTA溶液可有效地将金属离子从菌体上解吸下来,解吸后的菌体可重复使用。     

Metal uptake capacity of modified Saccharomyces pastorianus biomass from different types of solution

In this paper, we investigate the effect of different biomass pretreatments on metal ion uptake by various biosorbents. Heat-treated as well as caustic-treated and ground biomass of Saccharomyces pastorianus was used to remove copper, lead and cadmium from various solutions. Untreated yeast was used as the control sample. The effect of yeast modification on sorption capacity depended on the different types of heavy metal ions and whether they were in single- or multi-component solutions. The highest uptake of copper and lead from a single-metal solution was obtained from heat-treated cells. Ground biomass was the most efficient at cadmium removal. However, the sorption capacity of the modified biomass did not improve when metal ions were removed from multi-component solutions. Indeed, the results in this paper show that optimizing metal removal from single-cation solutions can lead to decreased sorption capacity in multi-component solutions. Therefore, while adjusting the procedure of biomass modification, not only the nature of the metal ion being sorbed but also the chemical composition of the metal ion solution should be taken into account.     

Comparison of the adsorption of lead,cadmium, copper,zinc and barium to freshwater surface coatings

Measurements were made regarding the adsorption of lead, cadmium, copper, zinc and barium to freshwater surface coatings (biofilms and associated minerals), which were collected in Nanhu Lake in Jilin Province, PR China, in order to investigate the variability of adsorption capacities of these heavy metals mentioned in the above surface coatings. The adsorption of lead and other heavy metals to the biofilms was observed to decrease in the following order: copper, lead, zinc, cadmium, and barium. Generally, the values of Gamma(max) (the maximum adsorption, micromol/m(2)) increased with the standard electrode potential of metal elements used and were recorded as 166.7, 40.0, 29.4, 10.8, and 1.8 for copper, lead, zinc, cadmium and barium, respectively. The values of 1/Gamma(max) increased linearly with the decrease in values of the standard electrode potential of metal elements with a significant correlation (n=5, p=0.01) and increased linearly with the increase in values of covalent radius of metal elements with a significant correlation (n=5, p=0.05). This indicates that standard electrode potential and covalent radius were two of the principal characteristics of metals employed, causing the variation of lead and other heavy metal adsorption to the surface coatings.     

Biosorption of zinc and copper from aqueous solutions by two freshwater green microalgae Chlorella pyrenoidosa and Scenedesmus obliquus

Purpose

The objective of this study was to determine the removal of zinc and copper by two freshwater green microalgae Chlorella pyrenoidosa and Scenedesmus obliquus and to investigate changes of algal ultrastructure and photosynthetic pigment.

Methods

Algal cells were exposed for 8 days to different initial zinc or copper concentrations. Heavy metal concentrations were detected by an atomic absorption spectrophotometer. Algal growth, ultrastructure, and photosynthetic pigment were analyzed by a microplate reader, transmission electron microscope, and spectrophotometer, respectively.

Results

Low zinc and copper concentrations induced increase in algal growth, whereas application of high zinc and copper concentrations suppressed the growth of both algae. High metal concentrations also decreased the photosynthetic pigments and destroyed algal cell ultrastructure. The zinc removal efficiency by both algae increased rapidly during the first day and thereafter remained nearly constant throughout the experiment. The copper removal efficiency by both algae increased slowly during the whole experimental periods. In all cultures, the quantity of both metals removed intracellularly was much lower than the adsorbed quantity on the cell surface.

Conclusions

Both strains of the microalgae had proven effective in removing zinc and copper from aqueous solutions, with the highest removal efficiency being near 100%. In addition, C. pyrenoidosa appeared to be more efficient than S. obliquus for removing copper ions. On the contrary, S. obliquus appeared to be more efficient than C. pyrenoidosa for removing zinc ions.     

Oribatid mite communities and metal bioaccumulation in oribatid species (Acari, Oribatida) along the heavy metal gradient in forest ecosystems

The responses of oribatid communities to heavy metal contamination were studied. Concentration of cadmium, copper and zinc in nine oribatid species along a gradient of heavy metal pollution was measured. Oribatid mites were sampled seasonally during two years in five forests located at different distances from the zinc smelter in the Olkusz District, southern Poland. The most numerous and diverse oribatid communities were found in the forest with moderate concentrations of heavy metals. Analysis by atomic absorption spectrophotometry revealed large differences in metal body burdens among species. All studied oribatid species appeared to be accumulators of copper with Oppiella nova, Nothrus silvestris and Adoristes ovatus characterized by the highest bioaccumulation factors. Most species poorly accumulate cadmium and zinc. The accumulation of heavy metals in the body of oribatids was not strictly determined by their body size or the trophic level at which they operate.     

Performance evaluation of intermediate cover soil barrier for removal of heavy metals in landfill leachate

This pilot-scale study evaluated the use of intermediate cover soil barriers for removing heavy metals in leachate generated from test cells for co-disposed fly ash from municipal solid waste incinerators, ash melting plants, and shredder residue. Cover soil barriers were mixtures of Andisol (volcanic ash soil), waste iron powder, (grinder dust waste from iron foundries), and slag fragments. The cover soil barriers were installed in the test cells' bottom layer. Sorption/desorption is an important process in cover soil bottom barrier for removal of heavy metals in landfill leachate. Salt concentrations such as those of Na, K, and Ca in leachate were extremely high (often greater than 30 gL(-1)) because of high salt content in fly ash from ash melting plants. Concentrations of all heavy metals (nickel, manganese, copper, zinc, lead, and cadmium) in test cell leachates with a cover soil barrier were lower than those of the test cell without a cover soil barrier and were mostly below the discharge limit, probably because of dilution caused by the amount of leachate and heavy metal removal by the cover soil barrier. The cover soil barriers' heavy metal removal efficiency was calculated. About 50% of copper, nickel, and manganese were removed. About 20% of the zinc and boron were removed, but lead and cadmium were removed only slightly. Based on results of calculation of the Langelier saturation index and analyses of core samples, the reactivity of the cover soil barrier apparently decreases because of calcium carbonate precipitation on the cover soil barriers' surfaces.     

Palygorskite as a feasible amendment to stabilize heavy metal polluted soils

The sorption behaviour of palygorskite has been studied with respect to lead, copper, zinc and cadmium in order to consider its application to remediate soils polluted with these metals. The Langmuir model was found to describe well the sorption processes offering maximum sorption values of 37.2 mg/g for lead, 17.4 mg/g for copper, 7.11 mg/g for zinc and 5.83 mg/g for cadmium at pH 5-6. In addition the effect of palygorskite amendment in a highly polluted mining soil has been studied by means batch extractions and leaching column studies. The soluble metal concentrations as well as the readily-extractable metal concentrations were substantially decreased at any concentration of palygorskite applied to soil (1, 2, 4%), although the highest decrease is obtained at the 4% dose. The column studies also showed a high reduction in the metal leaching (50% for lead, 59% for copper, 52% for zinc and 66% for cadmium) when a palygorskite dose of 4% was applied.     

Influence of initial pH on bioleaching of heavy metals from contaminated soil employing indigenous Acidithiobacillus thiooxidans

Bioleaching of heavy metals from contaminated soil was carried out employing indigenous sulfur oxidizing bacterium Acidithiobacillus thiooxidans. Experiments were carried out to assess the influence of initial pH of the system on bioleaching of chromium, zinc, copper, lead and cadmium from metal contaminated soil. pH at the end of four weeks of bioleaching at different initial pH of 3-7 was between 0.9 and 1.3, ORP between 567 and 617mV and sulfate production was in the range of 6090-8418mgl(-1). Chromium, zinc, copper, lead and cadmium solubilization ranged from "59% to 98%" at different initial pH. A. thiooxidans was not affected by the increasing pH of the bioleaching system towards neutral and it was able to utilize elemental sulfur. The results of the present study are encouraging to develop the bioleaching process for decontamination of heavy metal contaminated soil.     

Computational spectroscopic study of copper, cadmium, lead and zinc interactions in the environment

Molecular modelling has been used to investigate the interactions of various heavy metals, in order to understand and possibly to control the nature and behaviour of metals, especially in the aquatic environment. The interactions of copper, cadmium, lead and zinc with organic acids were studied using density functional theory (DFT) calculations. Carboxylic acid was used as a model molecule. The structure of each metal carboxylate was optimized and the vibrational spectrum calculated. The results indicate that there is a shift in the calculated v_S(C=O) of metal carboxylates compared with that of carboxylic acid. It was also found that hexaaqua structures of both cadmium and zinc are stable whereas those of copper and lead are not. Furthermore, dipole moment calculations indicate that cadmium carboxylate dihydrate is more representative of cadmium interactions in the aquatic environment. Moreover, hexaaquo cadmium could further interact with surrounding molecules in the aquatic environment.     

Removal of copper from water by electrocoagulation process—effect of alternating current (AC) and direct current (DC)

Purpose and aim

In general, direct current (DC) is used in an electrocoagulation processes. In this case, an impermeable oxide layer may form on the cathode as well as corrosion formation on the anode due to oxidation. This prevents the effective current transfer between the anode and cathode, so the efficiency of electrocoagulation processes declines. These disadvantages of DC have been diminished by adopting alternating current (AC) in electrocoagulation processes. The main objective of this study is to investigate the effects of AC and DC on the removal of copper from water using magnesium alloy as anode and cathode.

Materials and methods

Magnesium alloy of size 2.0 dm² was used as anode and as cathode. To optimize the maximum removal efficiency, different parameters like effect of initial concentration, effect of temperature, pH, and effect of current density were studied. Copper adsorbed magnesium hydroxide coagulant was characterized by SEM, EDAX, XRD, and FTIR.

Results

The results showed that the optimum removal efficiency of copper is 97.8 and 97.2 % with an energy consumption of 0.634 and 0.996 kWh/m³ at a current density of 0.025 A/dm², pH of 7.0 for AC and DC, respectively. The adsorption of copper is preferably fitting the Langmuir adsorption isotherm for both AC and DC respectively. The adsorption process follows the second-order kinetics model with good correlation. Temperature studies showed that adsorption was endothermic and spontaneous in nature.

Conclusions

The magnesium hydroxide generated in the cell removes the copper present in the water, reducing the copper concentration to less than 1 mg/L, making it safe for drinking. The results of the scale-up study show that the process was technologically feasible.     

Exploring the metal phytoremediation potential of three <Emphasis Type="Italic">Populus alba</Emphasis> L. clones using an in vitro screening

Purpose  

This work was planned for providing a useful screening tool for the selection of Populus alba clones suitable for phytoremediation techniques. To this aim, we investigated variation in arsenic, cadmium, copper, and zinc tolerance, accumulation and translocation in three poplar clones through an in vitro screening. Poplars have been widely proposed for phytoremediation, as they are adaptable to grow on contaminated areas and able to accumulate metals. The investigation of possible differences among poplar clones in metal tolerance and accumulation deserves to be deeply studied and exploited for the selection of the more suitable tool for phytoremediation purposes.     

Haneş and Valea Vinului (Romania) closed mines Acid Mine Drainages (AMDs) – Actual condition and passive treatment remediation proposal

Acid Mine Drainages (AMDs) from Hane? and Valea Vinului (Romania) closed mines were considered for characterization and treatment using a local zeolitic volcanic tuff, ZVT, (M?cica?, Cluj County, Romania). Water samples were collected from two locations, before and after discharging point in case of Hane? mine, and on three horizons in case of Valea Vinului mine. Physico-chemical (pH, total solid, heavy metal ions concentration) analyses showed that the environment is strongly affected by these AMD discharges even if the mines were closed years ago. Iron, manganese and zinc were the main pollutants identified in Hane? mine AMD, while zinc is the one mainly present in case of Valea Vinului AMD. A batch technique (no stirring) in which the ZVT was put in contact with the AMD sample was proposed as a passive remediation technique. ZVT successfully remove heavy metal ion from AMD. According to heavy metal ion concentrations, removal efficiencies are reaching 100%, varying as follows, Fe²⁺ > Zn²⁺ > Mn²⁺. When the ZVT was compared with two cationic resins (strong, SAR and weak acid, WAR) the following series was depicted, SAR > ZVT > WAR.     

Biosorption of cadmium and copper contaminated water by Scenedesmus abundans

Experiments were conducted comparing the individual removals of cadmium and copper from water via biosorption using Scenedesmus abundans, a common green algae, to removal in a multi-component system to determine competitive effects, if any, between the metals. The goal was to characterize the biological treatment of water contaminated with heavy metals using live aquatic species. In addition, experiments were performed to measure cell viability as a function of metal concentration and also to compare metal removal using living species to that using nonliving ones. It was shown that, while both living and nonliving S. abundans removed cadmium and copper from water, living algae significantly outperformed nonliving algae. Further, in characterizing biosorption by three concentrations of live S. abundans, capacity curves were created comparing the metal biosorbed per mass algae to the initial metal concentration in solution. The algae concentration was not a factor in the biosorption of either metal individually, such that the capacity of the algae for the metal increased with decreasing algae concentration. At the lowest algae concentration considered, competitive effects were observed at copper and cadmium concentrations above 4 mg/l each. At the highest algae concentration considered, no competitive effects were observed in the range of cadmium and copper concentrations studied (1-7 mg/l). It was concluded that biological treatment of heavy metal contaminated water is possible and that at adequately high algae concentrations, multi-component metal systems can be remediated to the same level as individual metals.