All-Biomass Double Network Gel: Highly Efficient Removal of Pb²⁺ and Cd²⁺ in Wastewater and Utilization of Spent Adsorbents

Abstract

Besides excellent adsorption performance of adsorbents, the disposal of spent adsorbents should be considered for environmental concern. In this study, a new all-biomass double network Jute/sodium alginate (Jute/SA) gel is prepared via the simple dripping technique. 80 wt% water of Jute/SA hydrogel endows the adsorbent with high permeability for heavy metal ions diffusion onto internal adsorption sites. The Jute/SA gel adsorbent can efficiently remove heavy metals from melting wastewater, especially Pb²⁺ and Cd²⁺. The adsorbent shows high adsorption capacities of 291.3 mg g⁻¹ for Pb²⁺ and 149.9 mg g⁻¹ for Cd²⁺ at 298 K. The adsorption equilibrium reaches within 45 min for 45 mg L⁻¹ Cd²⁺ and Pb²⁺ using 1 g L⁻¹ adsorbent, showing 98% removal efficiency of Pb²⁺ and Cd²⁺. Moreover, the removal efficiencies in 45 min reach up to 99.1% for Pb²⁺ (7.539 mg L⁻¹) and 89.9% for Cd²⁺ (4.743 mg L⁻¹) in actual melting effluent containing Zn (43.95 mg L⁻¹), Cu (16.50 mg L⁻¹), Mn (19.24 mg L⁻¹), Ni (4.90 mg L⁻¹) and Fe (33.75 mg L⁻¹) using 1 g L⁻¹ adsorbent. The concentrations of Pb and Cd decrease below 0.001 mg L⁻¹ using 4 g L⁻¹ adsorbent. Furthermore, the adsorption efficiencies for Pb²⁺ and Cd²⁺ remain above 95% in the tenth cycle, and the desorption efficiency is up to 99%. In addition, the spent Jute/SA gel was a good organic fertilizer for plant growth. This work develops an efficient and eco-friendly biomass adsorbent for the removal of heavy metals in actual wastewater.