2-Mercaptobenzothiazole impregnated cellulose prepared by ultrasonication for the effective adsorption of precious metal palladium

• Cellulose–Mercaptobenzothiazole adsorbent prepared by ultrasonication.
• Adsorbent used to recover palladium from a catalyst.
• The system shows adherence to D–R and Langmuir model.
• The maximum adsorption capacity of Pd(II) was 5.00 mg/g.
• The process is exothermic.

Cellulose, a natural biodegradable polysaccharide is bestowed with very good features to promote diverse applications. In this work, we report the adsorption of palladium involving its interaction with cellulose and 2-mercaptobenzothiazole. The application of FT-IR, SEM and XRD studies were used to characterize the adsorbent as well as comprehend the mechanism of the adsorption process. The ligand impregnated cellulose was prepared by ultrasonication for 20 min. The FT-IR studies showed the participation of hydroxyl functional groups in cellulose and the soft sulfur atom in mercaptobenzothiazole in the bonding between palladium and the ligand impregnated biopolymer. The stable palladium chelate is adsorbed on the surface of the ligand modified biopolymer. The concentration of palladium in the aqueous phase was measured using diphenylthiocarbazone as the complexing agent at a wavelength maximum of 584 nm. The other factors affecting adsorption such as the optimum pH, kinetics, isotherm models and thermodynamics were studied in detail. The ligand impregnated biopolymer sorbent could be regenerated using thiourea. The extraction of palladium using thiourea was confirmed from the bathochromic shift of the palladium-thiourea complex to 248 nm. As an interesting application, the mercaptobenzothiazole impregnated cellulose could be tested to recover palladium from Bis(triphenylphosphine)palladium(II)dichloride which is used in palladium catalyzed coupling reactions.

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