Removal of some Heavy Metal Ions from Aqueous Solutions Utilizing the Jordanian Natural Zeolites

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Saudi Digital Library
Chemical contaminants, in particular heavy metals are more serious for its negativedirect and indirect impact. Lead, Cadmium and Cobalt are highly toxic still they arefound in water. Endless efforts worldwide have been addressing the problem. Latesttechniques involve the adsorption process for treating waste water, whereas abundantadsorbents are effective in this matter. In this study we investigated geo-sorbentmaterial that is Jordanian natural zeolite (JNZ), for reasons such as: its huge reserves inJordan, estimated by 1 billion tons, low cost, chemical and thermal stability and itsadsorptive properties.Three samples of JNZ namely: Al Hala (HL), Hannon (HN) and Mukawir (MK), werecharacterized as by the following instruments: Fourier Transform InfraredSpectrophotometer (FTIR), X-Ray Diffraction (XRD), Thermogravimetric Analysis(TGA), BET Surface Area Analyzer, and Scanning Electron Microscopy (SEM).The adsorption experiments were conducted at certain conditions: (0.01g), (30oC), (20ppm), (180 min) and (150 rpm). Where the effects of: pH, adsorbent mass, metal ionconcentration, time and temperature were studied, and attained satisfying yet highpercentage removal (%) and maximum adsorption capacity, in comparison with othercommon geo-sorbents, see (table 3-10 ).Adsorption Isotherms results assumed better fitting with the Langmuir and FreundlichIsotherms, suggesting a combined mechanism.The maximum adsorption capacities (mg/g) for HL, HN and MK, respectively asfollows:(Pb): 243.9, 166.666, 142.857•(Cd): 55.555, 52.631, 47.619•(Co): 52.631, 41.666, 30.303Correlation coefficient R2= 0.999 in the kinetic Studies strongly implies pseudo-secondordermodel for Pb, Cd and Co, indicating the chemical nature of the adsorption102process. Also the thermodynamic parameters for the adsorption process indicated theprocess was spontaneous, endothermic and accompanied with increased randomness.Overall:•The selectivity of metal followed the literature: Pb>Cd>Co, as a reason forthe ionic radius and hydration energy.•The HL sample obtained the largest among the samples for containingmixture of minerals and its hydrophilic nature which is very important forthe adsorption process; HL sample in particular had the highest hydrophiliccharacter with 2.51 Si/Al ratios.•The HL sample was preferable for Co, as SEM images support.•MK sample obtained the highest percentage removal (%), for its largersurface area, microporous nature, also for its chabazite content as well asits high percentage of exchangeable CaO.