Optimization of adsorbent dose and contact time for the production of jackfruit waste nutrient-enriched biochar

Raw biochar can be enriched with nutrients from digestates through adsorption producing nutrient-enriched biochar. The nutrient-enriched biochar can be used as a soil amendment to support sustainable agriculture. This study assessed the effect of adsorbent dose and contact time on the jackfruit waste biochar adsorption of essential nutrients of nitrogen, phosphors and potassium from the digestate. Response surface methodology (RSM) using central composite design (CCD) was utilized to optimize the adsorbent dose and contact time during the adsorption process. An adsorbent dose of 20–70 mg/g and contact time range of 48–120 h were used in this study. The optimal adsorbent dose and contact time were found to be 20 mg/g and 114.6 h, respectively. The corresponding optimum nitrogen, phosphorus and potassium adsorbed were 17.44, 20.94, and 21.36 mg/g, respectively. Models for the prediction of these values for nitrogen, phosphorus and potassium had R² values of 0.9801, 0.9804 and 0.9843, respectively, and non-significant lack of fit (p<0.05). This indicates the suitability of the models in predicting the adsorption conditions of adsorbent dose and contact time to produce high-quality nutrient-enriched biochar.

Graphical abstract