High concentration of nitrogen recovery from anaerobic digested slurry (ADS) using biochars: adsorption and...

Biochar produced from biomass has been increasingly used as an environmentally friendly and low-cost adsorbent. This study systemically evaluated the effects of raw materials including corn straw (CS), cattle manure (CM), and cherry woods (CW) as well as pyrolysis temperature (400, 500, and 600 °C) on the physicochemical properties, such as morphological structure, element content, and surface functionality of biochars. The batch experiments of NH₄⁺-N adsorption using anaerobic digested slurry (ADS) confirmed that CM600 (biochar derived from CM at 600 °C) had the highest adsorption capacity of 18.16 mg·g^-1. The effects of coexisting ions in ADS, biochar dosage, adsorption time and initial concentration on NH₄⁺-N adsorption from ADS by the biochars were evaluated. The results of the batch equilibrium and kinetics experiments showed that Langmuir isotherm model and pseudo-second-order kinetic model well described NH₄⁺-N adsorption by the biochars, indicating that physical and chemical adsorption occurred simultaneously. Furthermore, compared to the biochar-modified method, the raw material-modified biochar (CM600-modified biochar) showed excellent adsorption capacity with a maximum of 69.82 mg·g^-1 (284% increase) for the high NH₄⁺-N concentration (4,000 mg·L^-1) from ADS. Therefore, it was concluded that high-concentration nitrogen recovery from ADS using modified biochar was an effective method.