Study on Adsorption of Phosphate in Water Environment by Mg–Al Modified Biochar

Excessive release of phosphate has gained prominence as a pivotal contributor to water contamination. Biochar, known for its abundant surface acreage and unparalleled adsorptive prowess, has been widely employed in aqueous remediation. Within the scope of this investigation, unprocessed biochar was derived from Chaetomorpha valida via pyrolysis methodologies involving temperatures ranging from 320 °C, 460 °C, 620 °C, and 860 °C, respectively. Mg-BC620, Al-BC620, and Mg–Al-BC620 were prepared using the co-precipitation method at the optimal temperature to maximize the resource utilization of Chaetomorpha valida. The physicochemical attributes of altered biochars were evaluated employing X-ray diffractometry and other analytical techniques. The influence of different factors on phosphate’s adsorptive aptitude of altered biochar was investigated, and the adsorptive behavior and mechanism of biochar were studied using diverse kinetics of adsorption and assortment of isotherm models. The outcomes revealed that the optimal pyrolysis temperature was 620 °C, and the altered biochar displayed a strikingly elevated affinity for phosphate sorption, outperforming the unaltered biochar. Among the modified biochars, Mg–Al-BC620 outperformed the rest, boasting an astonishing eradication rate of 94.92% when dosed at 8 g/L, maintaining a pH equilibrium of 7 in the solution, while confronting an inceptive phosphate density of 150 mg/L. The utmost threshold of adsorption proficiency predicted by the Langmuir equation was 228.130 mg/g, which was 88.56 times that of BC620. This modified biochar exhibits a strong affinity for phosphate and excellent adsorption selectivity, providing a promising avenue for the resource utilization of Chaetomorpha valida and has broad application prospects for scavenging phosphate in aqueous mediums.