SORPTION OF HEAVY METAL IONS ON A GRANULAR BENTONITE–TYRE PYROLYSIS CARBON SORBENT: EFFECT OF pH, KINETICS, FIXED-BED DYNAMICS AND REGENERATION
- Authors
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Taylakov Utkir Tahirovich
Navoi State University of Mining and Technologies, Navoi, Uzbekistan -
Jo‘rayev Shoxruh To‘lqinovich
Navoi State University of Mining and Technologies, Navoi, Uzbekistan
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- Keywords:
- heavy metals granular sorbent tyre pyrolysis char bentonite sorption kinetics thermodynamics fixed-bed column regeneration
- Abstract
- Waste tyres and metal-bearing industrial effluents are two linked environmental problems in mining regions. This study evaluated a granular sorbent made from bentonite and the carbon-containing residue of waste tyre pyrolysis (G-BU(opt), activated at 750 °C) for the removal of Fe(III), Cu(II), Zn(II), Ni(II), Pb(II), Cd(II) and Cr(VI) from aqueous solutions. Batch experiments examined the effect of initial pH (1.5–6.0), contact time (1–1440 min), temperature (293–323 K) and competition in an equimolar mixture; fixed-bed column tests and five sorption–desorption cycles were carried out with Cu(II). Cation removal increased from 6.24–18.53 % at pH 1.5 to 71.68–89.45 % at pH 6.0, which corresponds to 35.8–44.7 mg/g, whereas Cr(VI) removal reached a maximum of 34.56 % at pH 4.0. The pseudo-second-order model described the kinetics better than the pseudo-first-order model (adjusted R² of 0.9956–0.9991 and 0.9154–0.9513, respectively). Sorption was spontaneous (ΔG° from −2.57 to −3.94 kJ/mol) and endothermic (ΔH° from +5.36 to +6.09 kJ/mol). In the equimolar mixture the ratio of multi- to single-component uptake decreased in the order Pb(II) 0.86 > Cu(II) 0.77 > Zn(II) 0.69 > Cd(II) 0.67 > Ni(II) 0.65. In a 6 cm bed at 4 mL/min and C₀ = 100 mg/L, the Cu(II) breakthrough and exhaustion times were 15 and 65 min. After five regeneration cycles with 0.1 mol/L HCl the sorbent retained 75.38 % of its initial Cu(II) capacity.
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