Use of Typical Wastes as Biochars in Removing Diethyl Phthalate (Det) from Water

Diethyl phthalate (DEP), one of the six typical PAEs priority pollutants declared by the US EPA, has attracted tremendous attention due to its widespread pollution and was selected as the adsorbate in this study. Properties of biochar samples obtained from three different feedstocks, i.e., sawdust (SDBC), rice straw (RSBC), and giant reed (GRBC), pyrolyzed at 400 degrees C as well as their ability to adsorb DEP from an aqueous solution were investigated. The results showed that the adsorption kinetics were well fitted with the pseudo-second-order model (R-2 > 0.99) and the intraparticle diffusion model (R-2 > 0.98). The maximal adsorption capacity of the DEP by the prepared biochar was in an order of GRBC (46.04 mg g(-1)) > RSBC (31.54 mg g(-1)) > and SDBC (18.39 mg g(-1)). The higher adsorption capacity of DEP by GRBC is mainly attributed to the higher surface area. The reduction in adsorption capacity of the biochar against DEP with an increase in the solution pH (from 2.5 to 10.0) was possibly due to promoting the electrostatic repulsion between the DEP and the surface of the biochar. However, the increasing sodium ionic strength promoted the adsorption of the biochar, which could be interpreted by the reduced solubility of the DEP due to enhancing salting out effects as increasing sodium concentration. In addition, it was favorable for the adsorption of DEP onto the biochars at a lower temperature (15 degrees C) and the calculated Delta G(0) was less than zero, indicating that the adsorption was a spontaneous and exothermic process. These experiments designate that these derived biochars can be used as an inexpensive adsorbent for the purification of PAEs contaminated water.

Automated summary

This study investigated the adsorption of diethyl phthalate (DEP) by biochar samples derived from different feedstocks. The results showed that giant reed biochar had the highest adsorption capacity due to its larger surface area. An increase in solution pH reduced the adsorption capacity, while an increase in sodium ionic strength enhanced the adsorption. Additionally, the adsorption process was spontaneous and exothermic at a lower temperature.