Abstract
Cobalt(II) doped chitosan bio-composite was prepared, characterized and used to oxoborate separation from aqueous solutions. The adsorption process was carried out in a batch system. The effect of pH, temperature, time and initial boron concentration on the boron adsorption were tested. The maximum boron adsorption was reached at pH range 8.0–8.5 at room temperature and within 60 min. Calculations based on Langmuir and Freundlich models showed the heterogeneous nature of boron adsorption on Co-CTS bio-composite. On the base of research on optimization of pH and results from XRD and FTIR analysis it was found that boron adsorption by Co-CTS occurred through the co-precipitation and adsorption of B on cobalt hydroxide following the Coulomb attraction of B(OH)4− species on positively charged sites and molecular attraction of H3BO3 through hydrogen bond with amine or hydroxyl groups of chitosan. The modelling of the thermodynamic data indicated the nonspontaneous and exothermic nature of the adsorption process. The pseudo-second-order model adequately described the boron adsorption on Co-CTS hydrogel. Desorption by means of alkaline solution at pH 12 was carried out successfully. Adsorption–desorption efficiencies in 3 cycles were almost 100%.
Highlights
Boron dissolved in surface and ground waters is present at concentration levels of 0.3–100 mg/L and higher, anthropogenic and geothermal activity dependent [1, 2]
For kinetic studies 4.0 g of chitosan beads was added to a capped volumetric flask containing 100 mL of boric acid solution at pH of 8.5, aliquots were taken at appropriate time intervals after shaking on mechanical shaker and filtered as above
The grazing incidence X-ray diffraction (GIXD) patterns were recorded over a 2θ range from 10° to 80° with a 0.05° step size for the incident angle (α = 0.25°)
Summary
Boron dissolved in surface and ground waters is present at concentration levels of 0.3–100 mg/L and higher, anthropogenic and geothermal activity dependent [1, 2]. Boron is a significant micronutrient for plants, it is need only in small amounts. Its high levels are injurious and even lethal to plants. An excess of boron may lead to damage of the nervous system [3]. The boron concentration in water as well as wastewater is regulated in different countries throughout the world. The recommended level of boron in drinking and irrigating water and wastewaters discarded to the environment is 1.0 mg/L in Poland [4, 5] and in the European Union [6]. The boron concentration recommended for drinking water according to the World Health Organization guidelines is up to 2.4 mg/L [7]
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