Preparation of a novel hydrogel of sodium alginate using rural waste bone meal for efficient adsorption of heavy metals cadmium ion

Adsorption has been an important method for removing heavy metals from industrial wastewater. However, there has been a lack of an environmentally friendly, low-cost, biodegradable and easily recyclable material. China produces bones are not fully utilized leads to a waste of resources Therefore, efficient application of bone meal (BM) for reme-diation of contaminants in water would provide a promising alternative for resource utilization of bones. In this paper, we use a combination of BM and sodium alginate (SA) to prepare a novel BM/SA/calcium ion (BM/SA/Ca2+) double cross-linked composite hydrogel (BMSAH). Enhance the mechanical structure of SA while making the BM easy to re-cycle and reuse. The morphology and structure of the BMSAH were characterized using FT-IR spectroscopy and SEM -EDS. suggesting that the BMSAH can provide a larger specific surface area and high number of adsorption sites. The effects of the solution pH, ionic strength and contact time on the adsorption capacity of the BMSAH were investigated in depth, Under different conditions, BMSAH has a strong adsorption capacity of >90 %. XPS and FT-IR analysis showed that Cd2+ was adsorbed mainly via coordination interactions and hydrogen bonds with the carboxyl groups and nitrogen atoms in the BMSAH. A pseudo-second-order kinetic model, particle diffusion model and Isothermal ad-sorption lines indicate that the surface of the BMSAH is non-uniform suggesting that the adsorption of heavy metal ions by the BMSAH involves a combination of surface adsorption and intraparticle diffusion mechanisms, which is an over-all chemical-physical adsorption process. In addition, the adsorption capacity of BMSAH remained above 90 % after three desorption cycles. Our work provides a new method for the preparation of a low-cost, high mechanical perfor-mance, biodegradable and easily recyclable physical hydrogels used for the removal of heavy metal ions.

Automated summary

In this study, a novel double-crosslinked composite hydrogel was prepared using bone meal and sodium alginate, which showed high efficiency in removing heavy metals from wastewater. The hydrogel exhibited a larger specific surface area and high number of adsorption sites, enabling effective adsorption of heavy metal ions. Moreover, the hydrogel showed good recyclability and could be reused for multiple cycles.