Characterization and Adsorption Capacity of Modified Biochar for Sulfamethylimidine and Methylene Blue in Water

In this study, acomposite of pond mud and lanthanum- and nano-zerovalent iron-modified-biochar was investigated for its ability to adsorbmethylene blue (MB) and sulfamethazine (SMZ). La-modified attapulgiteand nano-zero valent iron (surface area enhanced by 43.7% via Brunauer-Emmett-Telleranalysis) were successfully loaded onto the straw-sediment biochar(BC) surface. With the increase in pyrolysis temperature, the biocompatibilityyield, the H, O, and N content, and the ratio of carbon elements decreased,while the pH value, surficial micropores, C element, and ash contentincreased. The biocarbon small molecules were gradually and tightlyordered, and the organic groups such as hydroxyl, carboxyl groups,and carbon oxygen double bonds were gradually lost or disappeared.The original Fe-BC had more phenolic hydroxyl groups forming an intermolecularhydrogen bond than others with a higher adsorption capacity possiblythrough the Schiff base reaction. The effect of various pH (2-9),temperature (15-35 & DEG;C), and initial concentration (1-25mg L-1) on adsorption was investigated. pH and temperaturewere the main factors governing the adsorption process. The maximumadsorption capacity was observed at pH 4. The adsorption performancesfor MB followed the order Fe-BC > La-BC > BC, and the maximumremovalrate was over 98.45% with pH = 7. The three types of BC dosages between0.2 (6.67 g L-1) and 0.4 g showed a removal rateof 99% for MB. The adsorption capacity of Fe-BC, La-BC, and BC forMB was 2.201, 1.905, and 2.401 mg L-1 with pH =4, while 4.79, 4.58, and 5.55 mg g(-1) were observedwith BC dosage at 0.025 g. For SMZ, the higher the temperature, thebetter the adsorption effect, and it reaches saturation at approximately25 & DEG;C. To further evaluate the nature of adsorption, Langmuir/Freundlich/Temkinmodels were tested and the adsorption capacities were evaluated onthe surface of the BC composite. The three modified materials werephysisorbed to SMZ, while MB was chemisorbed. For MB, the adsorptionperformance of BC is the best < 0.2 g (6.67 g L-1) at pH 7.0 at 35 & DEG;C. The Elovich model was more suitable forMB, while the Freundlich and Temkin models could better fit the adsorptionprocess of MB. The preparatory secondary dynamics equation and Langmuirequation were more compliant for SMZ, and the saturated adsorptioncapacities of straw-modified, La-BC, and Fe-BC reached 5.699, 6.088,and 5.678 mg L-1, respectively.