Iron–Carboxymethyl Sawdust for the Removal of Inorganic Phosphate from Water

Abstract

Inorganic phosphate (P i ) is critical to modern agriculture; however, agricultural drainage leaches P i into aquatic ecosystems leading to eutrophication. The valorization of agricultural byproducts is an effective method for enhancing the environmental performance of the agricultural sector. The aim of this study was to produce iron-coated sawdust capable of tightly binding P i and thus removing it from water. Sawdust was converted to carboxymethyl sawdust (CMSD) by reaction with NaOH and monochloroacetic acid. The carboxymethyl (CM) functional groups on CMSD tightly chelate iron to form iron−carboxymethyl sawdust (Fe-CMSD). The P i binding capacity (PBC) of Fe-CMSD was 16.1 ± 0.940 mg/g. The saturation curve fit well to the Hill− Langmuir isotherm with an apparent dissociation constant (K D App ) of 65.66 μM. Fe-CMSD is stable across the pH range found in agricultural drainage. Desorption of bound P i regenerates the PBC of Fe-CMSD, which retains 75.5% of its initial PBC after four binding−desorption cycles. Lab scale studies on variable flow rate systems using field water show cumulative removals of 88.8− 99.8% depending on flow rate. Therefore, Fe-CMSD shows promise as a P i adsorbent.

Long-Term Lead Immobilization in River Sediment by Ca(OH)2-Modified Rice Straw Biochar

“…When the pH was lower than 6.0, the zeta potential was negative, which indicated adsorption of Pb 2+ by electrostatic attraction. A higher pH can increase the surface charge mainly via deprotonation of hydroxyl and carboxylic groups. , …”

“…A higher pH can increase the surface charge mainly via deprotonation of hydroxyl and carboxylic groups. 52,53…”