Heavy metal removal from water solutions

Equilibrium and kinetic data for copper adsorption on chitosan and Lewatit S100 in batch systems have been obtained. For chitosan particles the best fit isotherm in the concentration range 0 – 8 g.m-3 is the R-P isotherm and for Lewatit S100-G the best fit isotherm in the concentration range 0 – 8 g.m-3 is the Langmuir isotherm. The maximum capacity of chitosan is slightly higher than that of Lewatit; however at aqueous concentrations below about 150 g.m-3 the amount of metal adsorbed on Lewatit is higher

Technological project of serpentine raw material milling from Dobšiná heaps

Serpentine heaps in the surrounding of Dobšiná are an old ecological problem of the city and at the same time a suitable material for the production of MgCl2 and SiO2. The technology of the production is based on the chemical processing of the raw material, which is preceded by the raw material preparation comprising of the mechanical and hydraulic sorting, milling and the magnetic separation operations

Removal of heavy metals from waste water using a hybrid membrane process

Soil and water pollution by heavy metals is currently a very important problem in environmental and other sectors. The origin of metals in water may be of either natural character (erosion of rocks and sediments, leaching of mineral resources) or anthropogenic character (mining and extraction of metals, industry, agriculture, etc.) (Martins et al. 2010). Many heavy metals, such as Pb, Cd, Cu, Zn, etc., are the most polluting factors in industrial wastewater and may get into the ground water. Subsequently they are bio-accumulated in living organisms and cause various diseases and disorders (Jamil et al. 2010). These problems need to be responded by developing new and more efficient methods for wastewater treatment (Martins et al. 2010). In practice several methods are used for removal of heavy metals from water. One of the promising methods for the removal of metal ions from water is a hybrid membrane processes. This method includes two processes – adsorption of metal ions on the natural zeolite and microfiltration of zeolite suspension through ceramic membrane. Experiments were carried out using model solutions containing Cu2+ ions (from CuSO4.5H2O and Cu(NO3)2.3H2O) and Zn2+ ions (from ZnSO4.7H2O and Zn(NO3)2.6H2O).In the experiments zeolite from Nižný Hrabovec localization (Zeocem JSC Bystré), Slovakia was used. Zeolite is mainly composed of mineral clinoptilolite (84%), other mineral are cristobalite (8%), clay (4%) and plagioclase (3-4%). Its structure is formed by three-dimensional network. Clinoptilolite is composed from silicate tetrahedron (SiO4)4- bound together by oxygen atoms, where part of the Si atoms is replaced with aluminum (AlO4)5-. This creates space structures with a number of cavities and channels, in which are accommodate metal cations and water molecules. The total volume of cavities is 24 to 32%. Zeolite has a bulk density of 1600 to 1800 kg.m-3, a specific gravity of 2200 to 2440 kg.m-3 and the specific surface of 30 to 60 m2.g-1 (www.zeocem.com).Adsorption experiments on model solutions were performed with the zeolite with particle size 20 microns. Before and after the experiments the concentrations of Cu and Zn were determined by atomic absorption spectrophotometry (AAS) using iCE 3300 AA Spectrometer Thermo Scientific. Solutions with concentrations of 10 to 5000 mg.l-1 were prepared from each of the chemicals. The solutions were shaken with 1 g of zeolite in 100 ml PET flasks on a shaker for 2.5 hours at 25°C and 220 rpm. The amounts of metals (Cu or Zn) in solutions were measured after stabilization, filtration and required dilution by AAS. The equilibrium between the concentration in solution and the adsorbed substance was evaluated using Langmuir, Freundlich and Redlich-Peterson models. According to the results of the adsorption experiments zeolite adsorbed of both the nitrates ions (Cu2+ and Zn2+) (equilibrium concentrations 1.48 mg.g-1 and 1.49 mg.g-1, respectively) best and the sulfate ions (0.34 mg.g-1 and 0.85 mg.g-1, respectively) less. Due to better adsorption capacities of zeolite for  ions derived from nitrates, further experiments were made from chemicals Cu(NO3)2.3H2O and Zn(NO3)2.6H2O.The next step was microfiltration of suspension of zeolite since a hybrid process for removal of Cu and Zn ions was used. Microfiltration was carried out at a constant pressure of 50 kPa, the flow rate of suspension 2.2 m.s-1 and various concentrations of zeolite (1 g.l-1 to 6 g.l-1). Tubular Membralox ceramic membrane was used, with length of 25 cm, internal diameter of 0.5 cm, external diameter of 0.7 cm and porosity of 50 nm. Active surface of the membrane was 49.48 cm2. Zeolite was added to the solution of ions circulating in the cross-flow microfiltration system. Metal ions were adsorbed by zeolite and the suspension was filtered by the membrane. The adsorbed metal remained circulating in the system and the permeat was purified water. Using this method, at suitable selection of the experimental conditions, up to 90 to 100% of metal ions can be removed from the solution

Adsorption efficiency of selected natural and synthetic sorbents

Sorbents are substances binding other substances on their surface. Effective sorbents have a porous surface. The adsorption activity of the surface is closely related to the local radius of curvature of surface irregularities. Suitable sorbents are natural and synthetic solids of amorphous or microcrystalline structure (Kyncl, Pavolová, Kyseľová, 2008). Globally, the following adsorbents are the most used: activated carbon, zeolites, silica gel, activated alumina (Bakalár et al., 2005). A characteristic of effective adsorbents is large surface area of hundreds of m2.g -1. Other important features of adsorbents include specific volume, porosity, average pore diameter, pore distribution, etc.For sorption of heavy metal cations some natural materials or industrial waste with high sorption capacity, which naturally reduces the overall cost of their disposal, can be used. Some of low-cost sorbents are: lignin, chitin, seaweed / algae, zeolites, clays, fly-ash, peat, sand grains coated with iron oxide, modified cotton and wool (Pavolová, Bakalár, Kyseľová, 2006).In experiments of Cu and Zn removal from wastewater the following adsorbents were used (Bakalár et al., 2005):Lewatit S100 is strongly acidic, gel-like cationic ion exchange resin with particles of equal size based on styrene-divinylbenzene copolymers. Monodisperse beads are chemically and osmotically highly stable.Chitosan is prepared from chitin, naturally occurring in the shells of crustaceans, by deacetylation using strongly alkaline solution. Chitin is a homopolymer composed of β-(1-4)-N-acetyl-D-glucosamine. The ability of crustaceans shells to bind metal ions is assigned to the presence of oxoskeleton in the molecule of chitin and chitosan.Synthetic zeolite, which is the included in the group of aluminosilicates, was prepared by zeolitization of fly-ash from energy industry.Bentonite is included in the group of hydrated aluminosilicates, the main ingredient is mineral montmorillonite.Slovakia is an inorganic composite sorbent made from pure natural ingredients.In removal of Cu2+, Zn2+ and Pb2+ cations the aspect of time, i.e. the time the specific sorbent reaches the maximum sorption capacity for the heavy metal removed, is also important. The experimental measurements of cations sorption using the above mentioned sorbents are made at the initial concentration of 10 mg.l-1 of heavy metal.The time aspect of separation of Cu2+ cations from model solutions of wastewater reached relatively very good results because the time to reach the equilibrium for all sorbent was about 60 seconds except for chitosan for which it was almost 2 minutes.The equilibrium of Zn2+ cations sorption was reached by about 80 seconds at the experimental measurements for all the selected sorbents except for chitosan for which this time was 2 minutes 5 seconds. This time was on average around 20 minutes longer compared to the sorption of Cu2+ ions.The sorption of Pb2+ cations was carried out at the experimental measurements in about 83 seconds for all the selected sorbents, except for synthetic zeolite for which the time was 1 min 15 s. The sorption of Pb2+ cations compared to the cations of Cu2+ was 23 s faster and compared to the cations of Zn2+ was 3 s longer.From the used sorbents the most appropriate for the removal of Cu2+, Zn2+, and Pb2+ is Lewatit S100, the equilibrium was reached in approximately 35 s, 45s, and 83 s for Zn2+, Cu2+, and Pb2+, respectively. According to the experimental measurements the longest adsorption time was for chitosan – about 2 minutes for Cu2+ and Zn2+, and about 1.5 minutes for Pb2+

Characterization of Cu(II) and Zn(II) Sorption onto Zeolite

In this study, a batch sorption study approach was combined with an instrumental analytical approach of atomic absorption spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) for the sorption of copper and zinc ions from aqueous solution on zeolites. Both copper and zinc are biogenic elements; nevertheless, many industrial processes produce an excessive amount, which is why their efficient removal from water must be studied. Two types of zeolites, Zeolite Micro 20 (Z-M20) and Zeolite Micro 50 (Z-M50), were used. The results showed that the maximum sorption capacities for removal of Cu and Zn were 1.06 for CuSO4, 42.35 for Cu(NO3)2, 1.15 for ZnSO4 and 2.29 for Zn(NO3)2 adsorption onto Z-M20 and 0.45 for CuSO4, 1.67 for Cu(NO3)2, 0.39 for ZnSO4 and 1.51 for Zn(NO3)2 adsorption onto Z-M50. The maximum sorption capacities are higher for sulfates and the sorbent with smaller particle size. The sorption capacities of Cu and Zn for corresponding anion and particle size differ only up to 5–15%. Using XRD and XPS analyses before and after the sorption process, it was found that the content of both Cu and Zn in the surface layer and the bulk are the same for sorption onto sorbent with smaller particle size, but are higher in the surface layer than in the bulk for sorption onto sorbent with larger particle size. One of the main findings of this study is that a zeolite with smaller particles takes Cu and Zn by the whole particle, while with bigger particles, Cu and Zn concentrate in the surface of the particle. The results of the study may be used as an indicator for sorption efficiency of the studied zeolites for their application in the treatment of copper and zinc contaminated effluents

A relation between the temperature of atmosphere and the sludge in the wastewater treatment aeration tank

Processes in the aeration tank remove nitrogen from organic substances from wastewater by using bacteria. Nitrification utilizes the metabolism of aerobic bacteria Nitrosomonas, Nitrococus, Nitrospira, Nitrobacter Nitrocystis and Nitrosobolus and the anaerobical bacteria Pseudosomonas, Chromobacterium, Denitrobacillus and Micrococus are denitrifying. The bacteria are litotrophic and they are sensitive to pH of wastewater. Chlorine, heavy metals and cyanide are toxic for bacteria. For a correct growth of reproduction and metabolism, the temperature above 10 ºC is needed but an ideal temerature is from 20 to 30 ºC. An intensive cold reduces or even stop the activity of bacteria but heating of the aeration tank prevents undercooling

Influence of zeolite suspension concentration on microfiltration characteristics [abstract] /

Tyt. z nagłówka.Artykuł jest abstr. referatu z konferencji.Bibliogr. s. 60.Crossflow microfiltration is a very effective and energy efficient separation method allowing separation of very fine particles from liquids. It is mainly used for separation of particles from 0.1 to 10 microns. These membrane processes are used for separation of solids from liquids in pharmaceutical, chemical, food, and dairy industries as well as in environmental protection and water treatment (Fadaei et al. 2007, Chellam et al. 2011). Ceramic membranes are often used for treatment of water. These membranes are preferred for their higher chemical, mechanical, and thermal resistance compared with organic membranes. Membranes form a physical barrier to the sludge, bacteria and suspended particles. Microstructural parameters as pore size, pore density, and porosity of the membrane have a great influence on the permeate f lux (Ogunbiyi et al. 2008, Altunkaynak et al. 2010). Zeolites occur in a number of variations such as clinoptilolite and chabazite. Clinoptilolite is the most abundant zeolite and is easily available in more than 40 varieties. Natural and also synthetic zeolites have unique physical, chemical and structural properties. Therefore zeolites are widely used in technological, environmental and agricultural processes. One of the most studied zeolites, clinoptilolite showed the highest selectivity for some heavy metals ions such as Pb2+, Cd2+, Zn2+ and Cu+ Babel et al. 2003). In the experiments natural zeolite was used from Nižný Hrabovec in the Slovak Republic. The structure is composed from three-dimensional grid, the main mineral is clinoptilolite. Clinoptilolite is composed of a tetrahedron (SiO4)4- connected by oxygen atoms, and a part of the silicon atoms is replaced with aluminum atoms. The total volume of the cavities of the zeolite is from 24 to 32%. The volume density is from 1600 to 1800 kg∙m-3, the density from 2200 to 2440 kg∙m -3 and the specific surface is from 30 to 60 m 2∙g -1 (www.zeocem.com). For the experimental measurements special laboratory microfiltration apparatus was used. The filtered suspension was pumped using a membrane pump from a reservoir (4 liters volume) into membrane module, in which the ceramic membrane with porosity of 50 nm is placed. Magnetic flow meter measured the flow of the suspension. The values of the input and output transmembrane pressure were recorded from gauges. From the membrane module permeate flowed to collecting bottle. The collecting bottle was placed on a labbalance. The monitored data (pressure, suspension flow rate, permeate flow and temperature) were processed by a computer program. The temperature of the suspension was maintained at 25°C, the pressures were in the range from 40 to 100 kPa and the flow rate of the suspension was 2.2 m∙s-1. The measurements were focused on determination of the stability of the microfiltration system using different pressures and different concentrations of suspensions of zeolite. Experiments were performed to determine the permeate fluxin the microfiltration of suspensions of zeolite at concentration of 3 g∙L-1, 6 g∙L-1 and 9 g∙L -1, at a constant pressure of 100 kPa and a constant rate of suspension flow of 2.2 m∙s-1. After stabilization of the system, and after the addition of a given concentration of zeolite to the apparatus in all three cases it is possible to see a decrease in membrane flux to a value of about 310 L∙m-2∙h-1. However this flux has not remained constant, but in the course of the experiment continued to decrease to a final value of 280 L∙m-2 h-1. This decrease indicates that under these conditions there is some fouling of the membrane at relatively low concentrations of the zeolite suspension. Due to membrane fouling experiments with gradual increasing and then decreasing of pressures were performed. In the experiments at a constant suspension f low rate of 2.2 m∙s-1 and a constant concentration of zeolite suspension of 3 g∙L-1 the pressure in the apparatus was gradually varied from 40 to 70 kPa and then back to 60 kPa and 50 kPa. For each of these pressures the system was allowed to stabilize for 30 min. From the comparison of the levels of flow rates at 60 kPa and 50 kPa it may be seen that in both cases a decrease in flux occurs after reduction of pressure. Therefore, it can be concluded that in the microfiltration experiments with the membrane and zeolite used it is preferably to use lower operating pressure of 70 kPa. In the following experiments therefore the pressure of 50 kPa was used. These experiments were carried out at constant pressure and constant rate of 2.2 m∙s-1. Concentrations of zeolite were varied by 1 g∙L-1 to a final concentration of 30 g∙L-1. The system was stable at low concentrations of zeolites and there was no initial decrease of flow. In the experiments with higher zeolite concentrations has also been shown that even at the highest concentration of used zeolite suspension of 30 g∙L-1 there was no decrease in membrane flux. This flux was approx. 150 L∙m-2∙h-1 and further did not decrease.Dostępny również w formie drukowanej.KEYWORDS: crossflow, separation, liquid

Application of organic waste for adsorption of Zn(II) and Cd(II) ions

Biosorption of Zn(II) and Cd(II) ions from aqueous solutions onto organic waste – orange peel, hazelnut shell, and walnut shell was studied using batch adsorption experiments. In the biosorption studies, equilibrium metal ion concentration was determined. Experimental data obtained were analysed in terms of Freundlich, Langmuir, Temkin, Dubinin–Radushkevich, Redlich–Peterson, Sips, Toth, and Khan isotherms. The results of the study showed that orange peel, hazelnut shell, and walnut shell can be adequately used as low-cost alternatives for the removal of Zn(II) and Cd(II) ions from aqueous solutions with maximum sorption capacities of 15.51 and 19.8 mg/g, 11.55 and 16.65 mg/g, and 26.60 and 21.10 mg/g, respectively. The highest removal efficiency of Zn(II) and Cd(II) ions was obtained for hazelnut shells. The process was fast and about 90% of metal ions were removed by all the studied biosorbents. The sorption process was possibly chemisorption occurring on a heterogeneous surface

Analysis and Model of River Basin Sustainable Management by SWOT and AHP Methods

The sustainable management of river basins is a comprehensive problem involving not only environmental quality but also socio-economic aspects. The primary objective of the study is to propose a sustainable management model of a river basin based on a clear identification of the good water quality in the river basin applicable for any river basin. The proposal is based on a monitoring of the quality of surface water in the basin, a quantitative and qualitative analysis of pollution, a questionnaire survey on the sewer systems and wastewater treatment in the basin and the diffuse sources of water pollution. For a better outline, a case study of Hornád river basin, Slovakia, was carried out. Two methodologies were applied: SWOT analysis for identification of indicators and the priorities and AHP analysis for a prioritization of the decisions. These analyses can be carried out for any activity based on identification of indicators and the priorities of the defined indicators to promote sustainable development. Based on the findings and the results of the analyses the model for managing the development of surface water quality in the basin was proposed. Generally applicable principles of sustainable development, accepting legislation in the field of water management, considering the quality of surface water in the basin, the impacts of wastewater discharges into the recipient, the identification and evaluation of positive and negative aspects of surface water quality, and the implementation of the proposed measures and post-implementation monitoring of qualitative development were covered in and by the proposed model