Abstract: In order to explore the possibility of utilization of green tidal alga—Chaetomorphavalida, three kinds of modified biochar were prepared from the green tidal alga at pyrolysis temperature of 450, 650, and 850 ℃, and at the optimum temperature, by incorporating metal (Fe, Mg, and Al) chlorides into the original biochar by co-precipitation method. The adsorption of phosphate on each biochar was evaluated by colorimetry. The adsorption characteristics of the optimal biochar were studied by fitting kinetic and isotherm adsorption equations, and the phosphate adsorption capacity of the optimal biochar was determined at pH from 3 to 11 and the biochar dose from 1 g/L to 25 g/L. The results showed that there was significantly higher phosphate adsorption capacity of the modified biochar at the optimum temperature of 650 ℃ than that of the original biochar (P<0.05), with the best effects via incorporating BC-650-Fe. The fitted Langmuir equation showed that the maximum adsorption capacity was (31.06±0.46)mg/g, and the actual measured maximum adsorption capacity was (27.70±0.11)mg/g, the adsorption equilibrium being observed within about 20 min. It was speculated that the adsorption behavior of BC-650-Fe on phosphate conformed to the uniform monolayer chemisorption by kinetic and isotherm adsorption equations. The phosphate adsorption capacity of BC-650-Fe was significantly influenced by water pH (P<0.05), with higher adsorption capacity in weak acidic and neutral environments, and increase with the increase in BC-650-Fe dosage. The removal rate of phosphate was found to be increased, with a negative correlation with the unit adsorption capacity. The maximal removal rate (93.16%) was observed under the conditions of the initial phosphate concentration of 50 mg/L, pH of 6 and the BC-650-Fe dose of 10 g/L. It is found that the pyrolysis temperature, water pH, and the amount of biochar have a great influence on the phosphate adsorption capacity of BC-650-Fe. The green tidal alga biochar modified with FeCl3 at 650 ℃ has good phosphate affinity, and has a broad application prospect of adsorbing phosphate in water, which can provide a new direction for the resource utilization of the green tidal alga.
2022, Vol. 37 
