Easy separable, floatable, and recyclable magnetic-biochar/alginate bead as super-adsorbent for adsorbing copper ions in water media

This work aimed to develop innovative material by combining properties of magnetic-biochar (derived from peanut shells) and hydrogel bead (MBA-bead) and apply it for adsorbing Cu2+ in water. MBA-bead was synthesized by physical cross-linking methods. Results indicated that MBA-bead contained similar to 90% water. The diameter of each spherical MBA-bead was approximately 3 mm (wet form) and 2 mm in (dried form). Its specific surface area (262.4 m(2)/g) and total pore volume (0.751 cm(3)/g) were obtained from nitrogen adsorption at 77 K. X-ray diffraction data confirmed Fe3O4 presented in magnetic-biochar and MBA-bead. Its Langmuir maximum adsorption capacity for Cu2+ was 234.1 mg/g (30 degrees C and pH(eq) 5.0). The change in standard enthalpy (Delta H degrees) of the adsorption was 44.30 kJ/mol (dominant physical adsorption). Primary adsorption mechanisms were complexation, ion exchange, and Van der Waals force. Laden MBA-bead can be reused several cycles after desorbing with NaOH or HCl. The cost was estimated for producing PS-biochar (0.091 US$/kg), magnetic-biochar (0.303-0.892 US$/kg), and MBA-bead (1.369-3.865 US$/kg). MBA-bead can serve as an excellent adsorbent for removing Cu2+ ions from water.

Automated summary

This study aimed to develop a new material, MBA-bead, by combining the properties of magnetic-biochar derived from peanut shells and hydrogel bead, and investigate its ability to adsorb Cu2+ in water. The MBA-bead contained a high water content of around 90% and had a diameter of approximately 3 mm (wet form) and 2 mm (dried form). It exhibited a specific surface area of 262.4 m(2)/g and a total pore volume of 0.751 cm(3)/g. The Langmuir maximum adsorption capacity of MBA-bead for Cu2+ was found to be 234.1 mg/g at 30 degrees C and pH(eq) 5.0. The primary adsorption mechanisms involved complexation, ion exchange, and Van der Waals force. Furthermore, the laden MBA-bead could be reused multiple times after desorbing with NaOH or HCl. The cost estimation for producing the materials indicated that MBA-bead has potential as an effective adsorbent for removing Cu2+ ions from water.