The lead and cadmium removal from wastewaters by natural and pretreatment zeolites was examined by using a batch-type method. The results demonstrated that the natural zeolites contained a complement ...of exchangeable Na, K and Ca ions but exposing them to 2 M NaCl solution at 22 and 70°C, respectively, converted them to a near homoionic state in Na-form. Lead and cadmium removal results using natural zeolites and treated zeolites showed that treatment improved both the exchange capacity and the removal efficiency. The influence of the temperature on the ion-exchange process was examined. It was found that the metal uptake was increased with increasing temperature during the ion-exchange process. Natural and modified zeolites remove toxic metals from waste waters.
The paper presents results of investigation of exchange of the clinoptilolite tuff cations with hydrogen ions from HCl solution of concentration 0.1 mmol cm
−3 and ammonium ions solutions of ...concentrations 0.0071 to 2.6 mmol cm
−3. Molal concentrations,
x (mmol g
−1) of cations exchanged in acid solution and in ammonium ions solutions were compared with molal concentrations of cations obtained by determination of the cation-exchange capacity of clinoptilolite tuff. The obtained results show that at ammonium ion concentrations lower than 0.1 mmol cm
−3, with regard to exchange capacity for particular ions, best exchanged are Na
+ ions, followed by Mg
2+ and Ca
2+ ions, while exchange of K
+ ions is the poorest (Na
+
>
Mg
2+
>
Ca
2+
>
K
+). At ammonium concentrations from 0.2 to 1 mmol cm
−3 the order is Na
+
>
Ca
2+
>
Mg
2+>
K
+. At concentrations higher than 1 mmol cm
−3 the order is Na
+
>
Ca
2+
>
K
+
>
Mg
2+. The results are a consequence of the uptake of hydrogen ions by zeolite samples in ammonium ions solutions at concentrations lower than 1 mmol cm
−3 and indicate the importance of Mg
2+ (besides Na
+ ions) for the exchange between clinoptilolite cations and H
+ ions, in contrast to K
+ ions, whose participation in the reaction with H
+ ions is the lowest. During decationization of the clinoptilolite in acid solution, best exchanged are Na
+, Mg
2+, and Ca
2+ ions, while exchange of K
+ ions is the poorest. Due to poor exchange of K
+ and H
+ ions and good exchange of Na
+, Mg
2+, and Ca
2+ ions, it is to be assumed that preservation of stability of the clinoptilolite structure is caused by K
+ ions present in the channel C. Clinoptilolite is dissolved in the clinoptilolite A and B channels where Na
+, Mg
2+, and Ca
2+ ions are present. On the acid-modified clinoptilolite samples, exchange of ammonium ions is poorer than on natural zeolite. The longer the contact time of the zeolite and acid solution, the worse ammonium ions exchange. It can be assumed that H
+ ions exchanged with zeolite cations are consumed for solution of aluminum in the clinoptilolite structure; therefore the concentration of H
+ ions as exchangeable cations decreases. In the ammonium ion solution at a concentration of 0.0065 mmol cm
−3, from the acid-modified zeolite samples, Al
3+ ions are exchanged best, followed by Na
+, Mg
2+, Ca
2+, and K
+ ions. Further to the results, it is to be assumed that exchangeable Al
3+ ions available from clinoptilolite dissolution are best exchanged with H
+ ions in acid solution.
The structure of (AsO
2)
−- and (HAsO
4)
2−-modified clinoptilolite samples from the two deposits (Vranjska Banja, Serbia and Donje Jesenje, Croatia) was studied using powder X-ray diffraction ...(XRPD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDXS) and X-ray photoelectron spectroscopy (XPS). Local environment of As ions was investigated by X-ray absorption spectroscopy (XAS). The pretreatment of clinoptilolite tuff by using first NaCl and later FeCl
3 solutions resulted in an arsenic uptake of up to 1.2
wt.%, whereas no As-uptake could be detected in the untreated zeolite. The X-ray photoelectron spectroscopy depth profile analyses of (AsO
2)
−- and (HAsO
4)
2−-modified samples show that As concentrations decrease from the surfaces towards the subsurface region of crystallites suggesting that the As atoms are mainly located at surfaces of crystallites. EXAFS (extended X-ray absorption fine structure) and XANES (X-ray absorption near edge structure) analysis revealed that arsenic cations in the samples arrange in the form of oxo-complexes attached to the iron cations on the surface of the clinoptilolite. The posttreatment of the samples with three different solutions of HCl confirmed irreversible sorption of arsenic in the zeolite by the chemisorption mechanism.
An evaluation of the application of electric furnace slag (EFS) as an adsorbent to remove Pb2+ and Cu2+ from industrial effluents is presented. The paper examines phase composition of EFS by using ...X-ray diffraction of powder. In the batch experiments, parameters studied include the effect of initial concentration of lead and copper ions, temperature, and contact time. Over the temperature range studied (293-313 K) the results of adsorption experiments could be fitted by using both Langmuir and Freundlich models and thermodynamic values of deltaG0, deltaH0 and deltaS0 corresponding to each adsorption process were calculated. Satisfactory conformity between experimental data and the model-predicted values was expressed by the correlation coefficient (R2). Both Langmuir and Freundlich models described the Pb2+ and Cu2+ sorption processes adequately, with correlation coefficient (R2) values ranging from 0.9760 to 0.9994. Data from this study indicated the potential use of the tested electric furnace slag, a by-product from "Felis" foundry in Sisak, Croatia, as Pb2+ and Cu2+ sorbents from the industrial effluents.
The objective of the present study was to investigate the removal of nitrogen in the form of ammonium ions (N-NH
+
4) from aqueous solutions using natural clay and zeolite. The Croatian zeolite ...clinoptilolite from the area of Donje Jesenje and Croatian bentonite clay from the Kutina area were used as natural filtration materials. Alkaline and acid modification of natural clay was performed. The N-NH
4
+ removal efficiency by clays in a dry state as well as in a liquid colloidal state have been investigated. The highest removal efficiency value for N-NH
+
4 (61.1 wt%) was achieved with the natural zeolite at the lowest used initial concentration, i.e. at a concentration of 100 mg N-NH
+
4/l. With the increase of the initial concentration of ammoniacal nitrogen, the removal efficiency quickly decreases. This is expected as zeolites and clays have limited sorption capacities. The practical aspect is important since an ammoniacal nitrogen elimination of more than 60.0 wt% for water containing less than 100 mg N-NH
+
4/l can be achieved. The ammoniacal nitrogen removal efficiency is higher for clays in a liquid colloidal state compared to the clays in a dry state. It has been found that the acid modification of the clay decreases the efficiency of ammoniacal nitrogen removal.
The aim of this work is development of methodology for analysis of inorganic cations (sodium, ammonium, potassium, magnesium and calcium) in fertilizer industry wastewater. Method development ...includes optimization of eluent flow rate and concentration of eluent competing ion in order to obtain optimal separation within reasonable analysis time. For that purpose artificial neural network retention model was developed and used in combination with normalized resolution product criteria function. Developed artificial neural network retention model shows good predictive ability R2 ≥ 0.9983. The determined ion chromatographic parameters enable baseline separation of all components of interest. By performing validation procedure and number of statistical tests it is shown that developed ion chromatographic method has superior performance characteristic: linearity R2 ≥ 0.9984, recovery = 99.81% − 99.44%, repeatability RSD ≤ 0.52%. That result proves that proposed method can be used for routine monitoring analysis in fertilizer industry.
In order to make a complete characterization of electric-arc furnace (EAF) dust, as hazardous industrial waste, and to solve its permanent disposal and/or recovery, bearing in mind both the volumes ...formed in the Croatian steel industry and experiences of developed industrial countries, a study of its properties was undertaken.
For this purpose, samples of EAF dust, taken from the regular production process in the Željezara Sisak Steel Mill between December 2000 and December 2001, were subjected to a series of tests.
The chemical composition of EAF dust samples was investigated by means of a several different analytical methods. The results from the chemical analysis show that the approximate order of abundance of major elements in EAF dusts is as follows: Fe, Zn, Mn, Ca, Mg, Si, Pb, S, Cr, Cu, Al, C, Ni, Cd, As and Hg.
Granular-metric composition of single samples was determined by applying sieve separation. Scanning electron micro-structural examination of EAF dust microstructure was performed and results indicated that all twelve EAF dusts were composed of solid spherical agglomerates with Fe, Zn, Pb, O, Si and Ca as the principal element.
The investigation of grain morphology and the mineralogical composition of EAF dust were taken by combination of high resolution Auger electron spectroscopy (HR AES), X-ray photoelectron spectroscopy (XPS) and X-ray powder diffraction analysis. The analysis of XPS-spectra determined the presence of zinc in the form of ZnO phase and the presence of lead in the form of PbO phase, i.e. PbSO
3/PbSO
4 forms.
The results of the X-ray diffraction phase analysis show that the basis of the examined EAF dust samples is made of a mixture of metal oxides, silicates and sulphates.
The metal concentration, anions, pH value and conductivity in water eluates was determined in order to define the influence of EAF dust on the environment.
A non-suppressed ion chromatographic method with conductometric detection is described for the simultaneous determination of six inorganic anions: fluoride, chloride, nitrite, bromide, nitrate and ...sulphate. The separation was achieved on a low-capacity anion-exchange column Metrohm IC Anion Column Super Sep, with a mobile phase consisting of phtalic acid dissolved in high-purity water, 2-amino-2-hydroxymethyl-1,3-propendiol and acetonitrile. In this work computer optimization procedures, using computer programs to select chromatographic conditions have been used, leading to the achievement of a desired separation. By using the different optimization methods in an integrated manner it is, however, possible to both speed method development, by reducing unnecessary experimentation, and to overcome the many shortcomings of each method, because of the different approaches. The purpose of this work is to improve and characterise the method for simultaneous determination of six inorganic anions in drinking water by non-suppressed ion chromatography, using optimization procedures, in order to be applied to the routine analysis. The proposed method has numerous advantages over the other widely used non-suppressed ion chromatography methods: higher selectivity, shorter analysis time, lower quantitation and detection limits. The performance characteristics of the method were established by determining the following validation parameters: precision and accuracy, linearity, detection limits and quantitation limits.
The wastewater treatment in the fertilizer factory in Kutina (Croatia) is carried out by an ion exchange process using strong acid cation and weak basic anion ion exchangers. The regeneration of ...cation exchange resin is performed by 56% HNO
3 while the anion resin regeneration is done by 16% ammonium hydroxide as an external regeneration process.
The wastewater in the investigation period contained a high content of nitrogen in ammonium form (with an average of 325
mg
l
−1 N-NH
4
+) as well as nitrogen in nitrate form (with an average of 201
mg
l
−1 N-NO
3). After treatment, the wastewater contained 8.7
mg
l
−1 of ammonium nitrogen and 7.0
mg
l
−1 of nitrate nitrogen and with the conductivity of 150
μS
cm
−1 it is added into the cooling water system.
As the nitrogen in collected wastewater is very high, the dilution is done prior to the ion exchange processing. The treated wastewater is a better choice for dilution process than decarbonisated water. In this case the exchange capacity of cation resin is higher by 9.3%.
Four types of anion resin were used at the wastewater treatment plant. The influence of 2% HNO
3 on LEWATIT S 4428 ion exchange resin was examined under laboratory conditions. Due to the effect of 2% HNO
3 on LEWATIT S 4428 anion resin during 24
days the exchange capacity decreased from the initial 1.19
mol
l
−1 to a final 0.71
mol
l
−1.
The dynamic contact of 2% HNO
3 with the same anion resin in the column results also in a decrease of the exchange capacity by 32%.This confirms the harmful influence of nitrogen acid on the nitrate binding capacity and resin stability.
Four types of anion resins were used under industrial conditions. Under dynamic equilibrium the best results were obtained with the LEWATIT S 4428 resin.
