Simultaneous and Efficient Capture of Inorganic Nitrogen and Heavy Metals by Polyporous Layered Double Hydroxide and Biochar Composite for Agricultural Nonpoint Pollution Control

Abstract

Agricultural nonpoint pollution has been recognized as the main source of aquatic contaminants worldwide, such as inorganic nitrogen (ION) and heavy metals (HMs). It is an important challenge to simultaneously and efficiently immobilize soil ION and HMs in farmland. Herein, we present a polyporous Mg/Fe-layered double hydroxide and biochar composite (Mg/Fe-LDH@biochar) with the efficient coadsorption capacity of ION and HMs for the mitigation of agricultural nonpoint pollution toward aquatic systems. The Mg/Fe-LDH@biochar showed strong adsorption toward ION (i.e., NH4 +–N and NO3 ––N) and HMs (i.e., Cu, Zn, Ni, Pb, and Cd), with maximum capacity of 98.53 mg of NH4 +–N/g, 27.09 mg of NO3 ––N/g, 295.80 of mg Cu/g, 141.70 mg of Zn/g, 75.59 mg of Ni/g, 1264.10 mg of Pb/g, and 126.30 mg of Cd/g, respectively. More attractively, by deionized water extraction, the adsorbed ION on the composite was more easily rereleased, with a desorption percentage of about 42.33 ± 6.87% NO3 ––N and 1.42 ± 0.78% NH4 +–N, than that of HMs (<1.0%). This difference is primarily related with the strength of bonding forces of ION and HMs when adsorbed on Mg/Fe-LDH@biochar, in the sequence of NO3 ––N (van der Waals force and electrostatic attraction) < NH4 +–N (hydrogen bonding) < HMs (ionic/coordinate bonding). Finally, to examine the performance of Mg/Fe-LDH@biochar for practical applications in farmland, column leaching experiments were successfully conducted by stimulated rainfall events. The addition of Mg/Fe-LDH@biochar into soils could greatly reduce the leaching of ION and HMs simultaneously, with reduction ratios of >60, >40, and >90% for NH4 +–N, NO3 ––N, and HMs, respectively, at 3.0% addition. Moreover, there was no leaching risk of Fe ions into the water body from Mg/Fe-LDH@biochar-amended soils.

Synthesis and characterisation of LDH‐type anionic nanomaterials for the effective removal of doxycycline from aqueous media

“…Moreover, the existence of the (003) peak confirms that the samples still preserve their layered morphology in the range of pH values tested. Such results indicate that the Mg–Fe LDH shows high chemical stability over a wide range of pH values which is in agreement adsorbent chemical stability with previously reported results (Zhang et al , 2018). Also, the chemical stability of prepared adsorbents was examined by determining the leaching percentage of magnesium in solution at different initial pH = 2.5–12.…”

Engineered Biochar Production and Its Potential Benefits in a Closed-Loop Water-Reuse Agriculture System

“…According to the proposed circular plan of agricultural waste utilization, plant residues, animal manures, and food wastes are recycled to produce engineered biochar are specifically designed for treating the wastewater generated from agricultural and domestic sources. At the same time, biochar can be applied to agricultural fields as a soil amendment to improve WUE [136], remediate diffuse-source contamination [137], and/or improve crop yields [48]; it can also be used as a clean fuel for energy supply (heading value >23 MJ/kg) [138,139]. It has been reported that the addition of biochar to soil could often enhance the plant available water (PAW) and WUE, although the soil type played an important role on the influence [140].…”

Wheat Straw Biochar as a Specific Sorbent of Cobalt in Soil

“…In a search for the most desired and efficient remediation material for cobalt, biochar should be considered. Due to the presence of a highly-porous structure [13], various functional groups (e.g., carboxyl, hydroxyl, and phenolic groups) [14] on biochar show a great affinity for metal cations [15]. The composition and biochar stability establish the sorption properties of the material.…”