Performance and mechanisms of NaOH and ball-milling co-modified biochar for enhanced the removal of Cd2+ in synthetic water: A combined experimental and DFT study

A multifunction magnetic carbonaceous adsorbent (MBM/OH/BC) was synthesized by facile NaOH and ball-milling co-modified biochar, and applied for removing Cd2+ in water. The results showed MBM/OH/BC exhibited excellent adsorption capacity (183.59 mg/g for Cd2+), short equilibrium time (60 min) and good reusability (the declining efficiency <20% after four adsorption and desorption cycles) compared with pristine biochar. Meanwhile, the modification mechanisms of NaOH and ball-milling to biochar were explored by a series of characterizations (XRD, SEM-EDS, BET, XPS and FTIR, et al). The results indicated the remarkable adsorption performance of MBM/OH/BC was mainly attributed to the co-modification significantly increased the specific surface area, mineral content and cation exchange capacity of biochar, thereby further improving the precipitation, cation exchange and complexation with Cd2+. In addition, the results of adsorption mechanisms showed that the joint contribution proportion to the total adsorption capacity of precipitation, cation exchange and complexation was up to 90%, indicating the three mechanisms were the primary adsorption mechanism. To sum up, NaOH and ball-milling co-modification was an effective strategy to increase the adsorption capacity of the pristine biochar for heavy metals from water. (C) 2022 The Author(s). Published by Elsevier B.V. on behalf of King Saud University.

Automated summary

A multifunctional magnetic carbonaceous adsorbent (MBM/OH/BC) was synthesized by co-modifying biochar with NaOH and ball-milling, showing excellent adsorption capacity for Cd2+ and indicating that the joint contribution proportion of three mechanisms to the total adsorption capacity was up to 90%.