Ammonium removal from groundwater using peanut shell based modified biochar: Mechanism analysis and column experiments

Abstract

Ammonium pollution caused by human activities threated to eco-environment and the groundwater was polluted by rain and other leaching processes. This study investigated the mechanism and dynamic adsorptive characteristic of ammonium (NH4+-N), which removed by a novel modified biochar (MBC) pyrolyzed from peanut shell. The maximum capacity of unmodified biochar (BC) and modified biochar (MBC) to ammonium absorption could reach 3.83 mg/g and 6.92 mg/g, respectively, indicating that modification would enhance the performance of the adsorbent. Analyzing a batch of experimental data, it can be found that the isothermal absorption was suitable for Sips model and the kinetic adsorption model suitable for quasi-second-order kinetic model, indicating that the adsorptive rate was related to the amount of the adsorption site and dominated by monolayers chemisorption. The characteristics of MBC before and after the process of adsorption showed that ion exchange, electrostatic adsorption and surface complexation were the main factors controlling adsorptive capacity. The dynamic removal performance of ammonium by MBC under different conditions was investigated by column experiments. The experimental data of breakthrough curve fitted the Thomas model well. The maximum adsorptive capacity (kTH = 5.28 × 10–3 L/(mg·h), and qe = 9.02 mg/g) was obtained when the influent concentration reached 30 mg/L, the bed depth 2.1 cm and the inflow rate 1 mL/min. It can be concluded that the MBC was a promising adsorbent which can effectively remove ammonium from groundwater.