Removal and recovery of phosphate from water by Mg-laden biochar: Batch and column studies

The work investigated the potential application of Mg-laden biochar prepared from Mg-enriched bamboo to remove and recover phosphate from water. The Mg-laden biochar samples were synthesized at 400 degrees C, 500 degrees C and 600 degrees C. With the increasing synthesized temperature, the production rate of adsorbent decreased but the Mg content and specific surface area increased. Factors on phosphate adsorption including kinetic, isotherm, pH, dosage were examined through batch experiments. The maximum phosphate adsorption amount was 344, 357 and 370 mg/g for biochar-Mg-400, biochar-Mg-500 and biochar-Mg-600, respectively. The effect of phosphate adsorption on Mg-laden biochar samples was also investigated by fixed-bed column experiments, and the maximum adsorption amount calculated by Thomas model was 60.7, 61.2 and 62.2 mg/g, respectively. The adsorbed phosphate could be successfully desorbed by 3M NaOH solution and the regenerated Mg-laden biochar samples could be reused at least 5 times for phosphate adsorption. The bioavailability of postsorption biochar was proved very well through the Mehlich 3 method. Phosphate adsorption characteristic and FTIR analysis indicated that the adsorption was mainly controlled by two mechanisms: ligand exchange and electrostatic attraction.