Screening of novel low-cost adsorbents from agricultural residues to remove ammonia nitrogen from aqueous solution

Most studies on ammonia adsorption from aqueous solution have been focused on mineral materials. However, a series of batch experiments were performed in this study to screen novel adsorbent materials from 80 agricultural residues, and to investigate the adsorption characteristics of six screened samples. The results showed that the ammonia adsorption efficiencies of 11 agricultural residues were comparable to those of minerals. The equilibrium data fitted well with both the Langmuir and Freundlich models, and the theoretical maximum monolayer adsorption capacities of strawberry leaves and stems, Boston ivy leaves and stems, southern magnolia leaves and poplar leaves were 6.71, 4.62, 6.07, 5.01, 6.22 and 6.25mg/g, respectively at 30 degrees C. The adsorptions reached equilibrium at about 18 h, and the kinetics were well described by the Logistic model. In conclusion, these agricultural residues could be used as adsorbent materials for ammonia removal.