MgO-modified biochar for the removal of dissolved humus from water and its potential application as a fertilizer

A series of MgO-modified biochars were prepared to remove dissolved humus from water. The samples were well characterized, and the results showed that Mg, in the form of MgO, was mainly deposited on the biochar surface. The adsorption capacity of the adsorbents increased with increasing Mg content, which indicated that MgO was the active site responsible for the adsorption of dissolved humus. The thermodynamics experiments indicated that dissolved humus adsorption onto BC/MgO-X was endothermic. The maximum adsorption capacity of BC/MgO-4 was 52.47-mg total organic carbon/g at 25oC. Moreover, the adsorbents were suitable for the treatment of wastewater with low dissolved humus concentration and demonstrated high adsorption selectivity for dissolved humus. To solve the treatment problem of adsorbents after dissolved humus adsorption, we attempted to recycle the adsorbents and apply them as fertilizers to improve plant growth. The pot experiments disclosed that the adsorbents after dissolved humus adsorption can effectively improve the root growth of plants.