Insight into the Adsorption of Nutrients from Water by Pyrogenic Carbonaceous Adsorbents Using a Bootstrap Method and Machine Learning

Herein, findings from 98 research papers [52 biochar (BC) and 46 activated carbon (AC) papers] were analyzed using a bootstrap method and a 95% confidence interval (CI) to provide insights into nutrient adsorption. The results indicated the solution temperature, pore volume, specific surface area, and pyrolysis temperature were correlated significantly to the maximum adsorption capacity (Q_m), achieving r values of 0.37, 0.23, 0.16, and 0.14, respectively. A statistically significant difference was witnessed for nitrate Q_m between AC and BC with median values of 17.64 and 0.51 mg/g, respectively, and CIs of 11.01-27.56 and 0.39-0.82 mg/g, respectively. In contrast, the difference in Q_m between AC and BC for phosphate and ammonium contained a high probability of chance. On average, engineered biochar achieved higher Q_m values of ammonium and phosphate (12.13 and 24.73 mg/g, respectively) in comparison with that of the original biochar. However, there is a good probability of no difference in nitrate between the two, albeit greater nitrate adsorption on the modified biochar with a mean Q_m of 3.03 mg/g. The tuned Cubist estimated equilibrium adsorption capacity with an R² of ∼0.90-0.91. The median and bootstrap 95% CI can be used as an average standard for designing adsorbate-adsorbent systems.