Herbs carbonization and activation for fast sorption of nitrate ions: a new challenge for a full treatment of groundwater pollution

Abstract

The evolution of low-cost ecotechnologies in water treatment and purification is highly increased. Face to the growing global demand for eco-friendly water treatment materials, the non-valorized herb-based biomass covering a large area could be a promising alternative. Herbs (HB) are currently one of the cheapest biomasses. Therefore, the utilization of HB for environmental applications is relevant. HB was treated and activated in this work to produce an eco-friendly adsorbent for nitrate removal from groundwater. HB was treated with modified carbonization at 220 °C to produce highly reactive biochar (BCH). Ammonium groups (AM) are immobilized covalently over the BCH surface, and then, the resulting materials BCH-AM are fully characterized. Results showed that ammonium is successfully grafted at the BCH surface, producing a highly stable material. Measurements on nitrate ion adsorption revealed that BCH-AM are of great interest as 80% of nitrate ions (NO₃^-) were removed. Importantly, the eco-friendly BCH-AM demonstrated the ability to easily desorb the nitrate ions using Na₂CO₃ as a green eluent. Parametric studies confirmed the effectiveness of the prepared adsorbent and approved that the adsorption occurred by electrostatic interactions. To demonstrate the performance of the adsorbent, BCH-AM was evaluated to remove NO₃^- from groundwater upstream in a water treatment plant. This work opens an immense perspective for herb biomass to be the actual challenge to resolve environmental problems.

Keywords: Adsorption; Ammonium; Biochar; Biomass; Groundwater; Nitrate ions.