Preparation of polyethylenimine and carboxymethyl cellulose co-modified magnetic bentonite for enhanced adsorption of Pb(II) and Cd(II) based on the concept of mesh bag and octopus-like tentacle

Magnetic bentonite (MB) is a cheap, effective and recyclable adsorbent for the removal of many pollutants. However, further enhancing the adsorption performance of pristine MB and eliminating the instability of Fe 3 O 4 magnetic particles in MB are vital and urgent for practical applications. Based on the principles of washing mesh bag and octopus tentacle, mesh-bag-like modifiers with tentacle-like structure of octopus were synthesized via grafted reaction of polyethylenimine (PEI) and carboxymethyl cellulose (CMC) to cover MB. As compared with the pristine MB, CMC-MB and PEI-MB, the magnetic bentonite adsorbent co-modified by PEI and CMC (CMC/PEI-MB) exhibited more multi-adsorption sites, stronger capture effects of tentacle for heavy metals and more effective mesh-bag-protection for Fe 3 O 4 . Attributed to these fascinating properties, CMC/PEI-MB achieved faster adsorption rates (the values of k 2 of Pb(II) and Cd(II) were 73.0 g mg ‒1 min ‒1 and 17.4 g  mg ‒1  min ‒1 ) and elevated adsorption capacities (760 mg g ‒1 and 470 mg g ‒1 ) for 1500 mg L ‒1 Pb(II) and 1000 mg L ‒1 Cd(II) in a wider pH range (3–7). Moreover, the reutilization rate of Pb(II) and Cd(II) over CMC/PEI-MB still remained 90% after five successive recycles. XRD and FT-IR results indicated that the structure of CMC/PEI-MB was well persevered after desorption, and the corresponding maximum desorption capacities of Pb(II) and Cd(II) from CMC/PEI-MB were 624 mg g ‒1 and 362 mg g ‒1 within 1 h, respectively. The findings of this study provide an interesting and effective approach for the construction of superior adsorbents basing on customary phenomena for the remediation of heavy metals from wastewater. Graphical Abstract