Enhanced removal of NO3-N from water using Fe-Al modified biochar: behavior and mechanism

Abstract

To remove NO3-N from water, coconut shell biochar (CSB) was modified by a solution of FeCl3, a solution of AlCl3 and a mixture solution of FeCl3 and AlCl3 respectively. The obtained modified biochar with the best effect of NO3-N adsorption was screened out to explore the adsorption behavior and mechanism of NO3-N removal by batch experiments and kinetics and thermodynamics and correlated characterization. The results indicated that the mixture solution of FeCl3- and AlCl3- modified CSB (Fe-Al/CSB) showed the best adsorption performance for NO3-N removal. Iron and aluminum elements existed on the surface of Fe-Al/CSB in the form of FeOOH, Fe2O3, Fe2+, and Al2O3 respectively. The adsorption process could reach equilibrium in 20 min. An acidic condition was favorable for NO3-N adsorption. The presence of coexisting anions was not conducive for NO3-N adsorption. The quasi-second-order model and Freundlich model could be well fitted in the adsorption process. The maximum adsorption capacity of Fe-Al/CSB fitted by the Langmuir model could reach 34.20 mg/g. The adsorption of NO3-N by Fe-Al/CSB was an endothermic and spontaneous process. Ligand exchange and chemical redox reaction were the NO3-N adsorption mechanisms which led to NO3-N adsorption by Fe-Al/CSB.

Increasing Surface Functionalities of FeCl3-Modified Reed Waste Biochar for Enhanced Nitrate Adsorption Property

“…Adel et al [12] obtained a lower adsorption ability of biochar after iron modification, which might be because the original conocarpus waste had fewer functional groups for binding with Fe 3+ /Fe 2+ . The high adsorption capacity could be explained by the combination of various modification processes and, thus, there being more adsorption sites for nitrate [18,34,35]. Therefore, the iron-modified biochar prepared in our study was preferable in terms of nitrate adsorption.…”

“…Li et al found that iron-modified reed biochar offered a higher adsorption capacity of 1.747 mg•g −1 for nitrate [16], for which the positively charged surface of iron-modified biochar attracted nitrate anions easily [17]. You et al suggested that introducing iron oxides to the biochar surface promoted a chemical redox reaction between Fe 2+ and NO 3 − -N, and obtained the maximum nitrate adsorption capacity of 34.20 mg•g −1 [18]. Iron modification was highly efficient for enhancing the adsorption properties of biochar for nitrate owing to its selectivity towards nitrate oxyanions in the adsorption process [19,20].…”

Hybrid Metal Oxide/Biochar Materials for Wastewater Treatment Technology: A Review

“…The maximum adsorption capacity of fluoride reached 196.1 mg/g, this being a satisfactory result. You et al 124 used iron and aluminum oxide modified biochar for nitrates removal. A coconut shell biochar was modified by a solution of a mixture of FeCl 3 and AlCl 3 , and after that composition studies revealed that iron and aluminum elements existed on the surface of Fe–Al/biochar in the form of FeOOH, Fe 2 O 3 , Fe 2+ , and Al 2 O 3 respectively.…”

Magnetic Mg-Fe/LDH Intercalated Activated Carbon Composites for Nitrate and Phosphate Removal from Wastewater: Insight into Behavior and Mechanisms

“…Similarly, Yin et al [ 20 ] inspected Mg-Al-modified biochar to eliminate nitrate and phosphate ions from nutrient-rich water and showed an outstanding affinity, with a maximum sorption capability of 41 mg/g for nitrate ions and 74 mg/g for phosphate ions. In another study, You et al [ 21 ] validated Fe-Al-modified biochar as an effective adsorbent for the removal of phosphate from wastewater. In the previously published study of our research group, a date palm-derived biochar intercalated with Mg-Al/LDH composites showed enhanced sorption capacities of nitrate and phosphate ions from a water solution; 178 and 28 mg/g, respectively [ 22 ].…”