High efficiency and selectivity of MgFe-LDH modified wheat-straw biochar in the removal of nitrate from aqueous solutions

• MgFe-LDH particles were incorporated into wheat-straw biochar.
• Biochar/MgFe-LDH composite showed a strong sorption ability to nitrate.
• Biochar/MgFe-LDH composite showed a high selectivity for nitrate.
• Adsorbent dosage of 5–10 g/L was the optimum for nitrate removal.

Mg–Fe layered double hydroxide (MgFe-LDH) particles were incorporated into wheat-straw biochar by liquid-phase deposition. The obtained biochar/MgFe-LDH composite was used to remove nitrate from aqueous solutions. X-ray diffraction patterns demonstrated that LDH particles were successfully deposited onto the carbon surface within the biochar matrix. Adsorption kinetic and isotherm studies and the effects of co-existing anions and adsorbents dosages were investigated using laboratory batch sorption experiments. The biochar/MgFe-LDH composite showed a strong sorption ability to nitrate in aqueous solutions with the Langmuir maximum adsorption capacity of 24.8 mg/g. A high selectivity for nitrate of the biochar/MgFe-LDH composite was also observed irrespective of the co-existence of sulfate and phosphate. The biochar/MgFe-LDH composite can thus be potentially used as an alternative adsorbent for the treatment of nitrate-contaminated waters as well as a soil amendment for the reduction of soil nitrate leaching.

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