Parthenium hysterophorus-derived iron-coated biochar: a sustainable solution for nitrate and phosphate removal from water

Water bodies face severe pollution from industrial operations and other human activities, endangering biotic life worldwide. Nitrate and phosphate contamination poses a significant challenge globally. This study focuses on developing an efficient adsorbent, derived from Parthenium hysterophorus (P. hysterophorus), for nitrate and phosphate removal from water. Biochar, termed P. hysterophorus stem biochar (SBC), was prepared at 650℃ and further coated with iron, creating iron-coated stem biochar (ICSBC), to enhance adsorption potential. SEM, TEM, EDX, and FTIR analyses characterized raw and coated biochars. Comparative adsorption studies revealed that P. hysterophorus ICSBC exhibited high adsorption capacity (nitrate = N = 77.17 mg/g, phosphate = P = 83.93 mg/g) and removal efficiency (nitrate = 88.19%, phosphate = 95.89%). Batch experiments explored the effects of contact time, adsorbent loading, pH, and initial concentration. Kinetic and equilibrium models demonstrated that the pseudo-second-order kinetic and Langmuir isotherm models best fit the data (R² values: N = 0.9644, P = 0.98122, N = 93.68, P = 92.97, respectively). ICSBC’s favorable attributes, including strong adsorption, low cost, and eco-friendliness, position it as an ideal adsorbent for nitrate and phosphate removal from contaminated water.