Pristine and manganese ferrite modified biochars for copper ion adsorption: Type-wide comparison

Area of Science:

• Environmental Chemistry
• Materials Science
• Adsorption Science

Background:

• Biochar is a promising adsorbent for removing heavy metals from water.
• Chemical modification of biochar can further improve its adsorption capacity.
• Manganese iron oxide (MnFe2O4) nanoparticles show potential for pollutant remediation.

Purpose of the Study:

• To synthesize MnFe2O4-modified biochars (MnFe2O4-biochars) from various feedstocks.
• To evaluate the Cu(II) adsorption performance of pristine and modified biochars.
• To investigate the role of surface properties, such as surface area and functional groups, in Cu(II) adsorption.

Main Methods:

• Nine different biochars were synthesized from various feedstocks.
• Biochar surfaces were chemically modified via MnFe2O4 precipitation at pH 11.
• Cu(II) adsorption was quantified using the Langmuir model at pH 6 and 25°C.
• Surface area and carboxyl group contributions were analyzed.

Main Results:

• MnFe2O4-biochars exhibited significantly higher maximum adsorption quantities (qmax) for Cu(II) compared to pristine biochars, with enhancements ranging from 65.6% to 246%.
• Adsorption capacity ranged from 32.7-43.1 mg/g for MnFe2O4-biochars, compared to 10.4-23.6 mg/g for pristine biochars.
• No correlation was found between surface area and Cu(II) adsorption for either pristine or MnFe2O4-biochars.
• Carboxyl groups on the biochar surfaces were identified as the primary contributors to Cu(II) adsorption.

Conclusions:

• Surface modification with MnFe2O4 substantially boosts biochar's capacity for Cu(II) removal.
• The biochar matrix primarily acts as a carrier for MnFe2O4, with carboxyl groups being key functional sites for adsorption.
• This approach offers an effective strategy for developing advanced adsorbents for heavy metal remediation.