Removal of Heavy Metal Ions from Industrial Wastewater by Scolecite

Scolecite is a tectosilicate mineral belonging to the zeolite group; it is a hydrated calcium silicate, CaAl2Si3O10•3H2O. Only minor amounts of sodium and traces of potassium substitute for calcium. There is an absence of barium, strontium, iron and magnesium [1,2]. Scolecite is isostructural (having the same structure) with the sodium-calcium zeolite mesolite and the sodium zeolite natrolite, but it does not form a continuous chemical series with either of them [1]. It was described in 1813, and named from the Greek word, σκώληξ='worm' because of its reaction to the blowpipe flame. Scolecite is a common zeolite. It is a mineral of secondary origin, and occurs with other zeolites in the amygdaloidal cavities (cavities filled with secondary minerals) of weathered basalts, also in gneisses and amphibolites, and in laccoliths and dikes derived from syenitic and gabbroic magmas, and in contact metamorphic zones. It is a hydrothermal mineral derived from low temperature alteration of basalts and related rocks, associated with other zeolites, calcite, quartz and prehnite. It can be found on top of the calcium zeolites heulandites, stilbite and epistilbite [2]. Associated minerals include quartz, apophyllite, babingtonite, heulandite, stilbite and other zeolites. Due to their structural characteristics, natural zeolites can be used in several applications, from which Pansini [3] reviewed those of environmental interest. For example Zamzow et al. [4] used clinoptilolite to remove Al, Fe, Cu, and Zn from copper mine wastewater to below drinking water standards. Ouki and Kavannagh [5] showed that clinoptilolite and chabazite differ in their performance regarding capacity and selectivity. Other authors have demonstrated natural zeolites exhibit excellent selectivity a number of hazardous cations, a very moderate environmental impact [6-8]. The characteristics of industrial wastewater vary widely from industry to industry, and even within the same industry, depending on the raw materials used, processes employed, and various other factors [9]. Natural zeolites are especially attractive for removing heavy metal ions from effluent wastewaters mainly of industrial origin [5]. Zeolite media is a versatile product; it works the same way as any cation exchanger. Ca2+, Mg2+ and heavy metals ions are replaced on one to one basis with sodium or potassium through the ion exchange process [11]. Our objective in this study is to investigate the removal of inorganic pollutants like Ni2+, Pb2+, Zn2+, Cd2+, Fe3+ and Cr3+ metal ions from a model solution by the scolecite natural zeolite (SNZ). Materials and Methods


Introduction
Scolecite is a tectosilicate mineral belonging to the zeolite group; it is a hydrated calcium silicate, CaAl 2 Si 3 O 10 •3H 2 O. Only minor amounts of sodium and traces of potassium substitute for calcium. There is an absence of barium, strontium, iron and magnesium [1,2]. Scolecite is isostructural (having the same structure) with the sodium-calcium zeolite mesolite and the sodium zeolite natrolite, but it does not form a continuous chemical series with either of them [1]. It was described in 1813, and named from the Greek word, σκώληξ='worm' because of its reaction to the blowpipe flame. Scolecite is a common zeolite. It is a mineral of secondary origin, and occurs with other zeolites in the amygdaloidal cavities (cavities filled with secondary minerals) of weathered basalts, also in gneisses and amphibolites, and in laccoliths and dikes derived from syenitic and gabbroic magmas, and in contact metamorphic zones. It is a hydrothermal mineral derived from low temperature alteration of basalts and related rocks, associated with other zeolites, calcite, quartz and prehnite. It can be found on top of the calcium zeolites heulandites, stilbite and epistilbite [2]. Associated minerals include quartz, apophyllite, babingtonite, heulandite, stilbite and other zeolites. Due to their structural characteristics, natural zeolites can be used in several applications, from which Pansini [3] reviewed those of environmental interest. For example Zamzow et al. [4] used clinoptilolite to remove Al, Fe, Cu, and Zn from copper mine wastewater to below drinking water standards. Ouki and Kavannagh [5] showed that clinoptilolite and chabazite differ in their performance regarding capacity and selectivity. Other authors have demonstrated natural zeolites exhibit excellent selectivity a number of hazardous cations, a very moderate environmental impact [6][7][8]. The characteristics of industrial wastewater vary widely from industry to industry, and even within the same industry, depending on the raw materials used, processes employed, and various other factors [9]. Natural zeolites are especially attractive for removing heavy metal ions from effluent wastewaters mainly of industrial origin [5]. Zeolite media is a versatile product; it works the same way as any cation exchanger. Ca 2+ , Mg 2+ and heavy metals ions are replaced on one to one basis with sodium or potassium through the ion exchange process [11]. Our objective in this study is to investigate the removal of inorganic pollutants like Ni 2+ , Pb 2+ , Zn 2+ , Cd 2+ , Fe 3+ and Cr 3+ metal ions from a model solution by the scolecite natural zeolite (SNZ).

Materials and Methods
The sample of natural zeolite scolecite collected from Bayouda desert. It locates west of Kadabas, and south of Nubian Desert. The Bayouda volcanic field located: There are four industrial wastewaters from:

2.
Paints factory in Khartoum industrial area.

3.
Petroleum water from Foloug field in Southern Sudan.

4.
Mahmoud Sharif's electricity station. Samples collected and stored in one liter plastic container, and kept in refrigerator.

Abstract
It is a strategic target now to reuse treated industrial waste water for washing, irrigation etc., to efficiently manage and maximize Sudanese's water resources. The aim of the present work was to study the performance of natural zeolite (scolecite) for removing heavy metals from industrial waste water. Natural zeolite deposit sample was collected from Bayooda desert. Natural zeolite used (scolecite) was characterized by XRD, XRF, SEM and FTIR instruments. The physical properties (pH, EC, TDS, COD, BOD, total hardness) and chemical properties (Ni 2+ , Pb 2+ , Zn 2+ , Cd 2+ , Fe3 + , Cr 3+ ) of the collected industrial waste water samples were investigated. Zeolite sorbed around 95. 8

Method
A sample of (scolecite natural zeolite) 2 g as Na-Zeolite (315-500 µm) grain-size was placed in a beaker. Before determined concentrations of heavy metal ions from industrial wastewater samples, adjusted to decrease (pH) with Nitric acid. Then was added 50 mL industrial wastewater which had six heavy metal ions (Ni 2+ , Pb 2+ , Zn 2+ , Cd 2+ , Fe 3+ , and Cr 3+ ) To facilitate extraction of the heavy metal ions. Stirring: vigorous shaking was applied for 10 min as contact time. The solution was then filtered at room temperature 25°C, and the filtrate was analyzed by (A.A.S) to determine the residual of the heavy metal ions concentration.

Results and Discussion
Results of scolecite were shown in Tables 1 and 2, the chemical composition of the natural zeolite as oxides. SiO 2 and AL 2 O 3 percentage were found high in sample. This indicates that silicate and aluminate are important components in natural zeolites. Percentages of metal oxides (Fe 2 O 3 + , CaO + , MgO + , Na 2 O + , K 2 O) were found (32.31%) and this indicates that all cations were exchanged by Na + ions to form sodium zeolite as cation exchanger. The exchange of multivalent metal ions can be achieved in low pH to ensure the solubility of heavy metal cations according to Blanchard [11]. Characteristics of Scolecite were drown in Figures 1-3. The identification of the zeolite was carried by X-Ray diffract meter (XRD), system: Philips, Model: X-pert PRO stress XRD analyzer Cu-target radiation, used in the present work phase analysis was achieved by using XRD, sample was analyzed and found to be scolecite Figure 1. SEM photograph of zeolite particles is shown in Figure 2. It is clear that particles are rectangular in shape with sharp edges. In the infrared spectrum shown in Figure 3  Results of industrial wastewater: Samples were shown in Table  3. Physiochemical properties of industrial wastewater samples were drown in (Figure 4), Indicates pH for tannery wastewater (3.56), and pH for paints wastewater (8.40). In comparison the Arab Industrial Development and Mining Organization (AIDMO) standards (May 2001) where pH range [6][7][8][9], tannery wastewater is acidic, and paints wastewater is acceptable.
In comparison the AIDMO standards where the concentrations of total dissolved solids (TDS) does not exceed (1200 ppm), tannery wastewater (32100 ppm) has a very high value, where electricity wastewater (435 ppm) has acceptable value. This explains the high conductivity of tannery wastewater (53.100 µs/cm).
In comparison the AIDMO standards for biological oxygen demand BOD (30 ppm), tannery wastewater has a high value (53.34 ppm), while and paints wastewater is acceptable (7.5 ppm). Chemical oxygen demand (COD) in tannery wastewater (3000 ppm), and petroleum wastewater (112 ppm) are high in comparison the AIDMO standards (10 ppm). Total hardness in tannery wastewater is 1012.78 ppm, but it is much lower in petroleum wastewater (34.56 ppm). High concentrations of heavy metal ions were shown in Table 4. Thus it is concluded that tannery wastewater has many pollutants discharged directly without treatment to the river. Removals of heavy metals by scolecite were drowning in used SPSS IBM version 20 were shown in

Physical properties
Color Domestic and industrial wastes, natural decay of organic materials.

Solids
Domestic water supply, domestic and industrial wastes, soil erosion, inflow, and infiltration.

Chemical constituents
Heavy metals Industrial wastes.
pH Domestic, commercial, and industrial wastes.

Nitrogen
Domestic and agriculture wastes.

Sulfur
Domestic water supply, domestic, commercial and industrial wastes.

Methane
Decomposition of domestic wastes.

Archaebacteria
Domestic wastes, surface water infiltration, treatment plants.