Phosphorus Removal from Aqueous Solution by Pre- or Post-Modified Biochars Derived from Agricultural Residues

Biochar produced from agricultural residues through pyrolysis has the characteristics of large specific surface area and porous structure and thus can be used as an adsorbent for various contaminants. In this study, five types of agricultural residues, peanut shells (PS), mung bean shells (MBS), rice husk (RH), corn cob (CC), and cotton stalks (CS), were selected as feedstocks to prepare biochars. Magnesium chloride (MgCl2; 5 mol L-1 m) solution was used as a modifier to prepare pre-modified and post-modified biochar adsorbents. The modified biochars were used in adsorption experiment to test their sorption ability to phosphate from aqueous solution. Model simulations and analysis were used to determine phosphorus removal mechanisms. Experimental results showed that the phosphate removal efficiency of the pre-modified cotton stalk paralyzed at 600 degrees C (Pre-CS600) was the best with adsorption capacity of 129.9 mg g(-1). The results also showed that the adsorption capacity of the biochar pre-modified by MgCl2 was much better than that of unmodified and post-modified ones, suggesting the pre-modification method can be used to prepare modified biochars for the removal of phosphorus from aqueous solution.