Biochar–nZVI nanocomposite: optimization of grain size and Fe0 loading, application and removal mechanism of anionic metal species from soft water, hard water and groundwater

Abstract

This work for the first time evaluates the efficiency of biochar-supported nanoscale zerovalent iron (nZVI) particles combinedly as a function of biochar grain size and iron loading for the removal of anionic metal species, i.e., HCrO 4 − and CrO 4 2− . Both the factors are crucial and have to be optimized in order to achieve the highest and fastest removal. Not only that, it is also crucial to check the applicability of that composite in complex aqueous solutions. For that, nZVI particles were supported on biochar grains of different size ranges, i.e., < 75 µm (IBC-< 75), 75-150 µm (IBC-75-150), 150-300 µm (IBC-150-300) and 300-600 µm (IBC-300-600) with Fe/BC mass ratio = 1. Further, to check the effect of iron loading, < 75 µm grains were modified with iron at Fe/BC = 0.5 (IBC-0.5) and Fe/BC = 2 (IBC-2). All these composites were evaluated for the removal of anionic Cr(VI) species in distilled water (DW). Obtained results suggest that maximum (Q max = 16.30 mg/g) and fastest (100% within 5 min) removal of 10 mg/L Cr (VI) solution was obtained with IBC-< 75. The applicability of IBC-< 75 was further evaluated for Cr(VI) removal from different waters, i.e., soft water (SW), hard water (HW) and groundwater (GW). Results show that complete removal of 10 mg/L Cr(VI) was faster in DW (within 5 min) followed by SW ≈ GW (10 min) and then in HW (20 min), while the order of Q max was GW (22.49 mg/g) > SW (21.54 mg/g) > HW (17.00 mg/g) > DW (16.30 mg/g). Cr(VI) removal mechanisms were chemisorption, reduction and simultaneous coprecipitation as confirmed through various kinetic and isotherm modeling and through pXRD of reaction precipitates.

Continuous Filtration of Multimetal-Contaminated River Water and Groundwater Using Antioxidants Preserved Redox-Sensitive Nanocomposites: Ultrahigh Reactivity and Self-Sedimentation Possibility

“…This antioxidant-modified biochar was further dispersed in an ethanol/water interfacial iron solution, and wet chemical reduction with NaBH 4 was done to form elemental iron-modified biochar. In this stage, a mass ratio of 1:1 of iron/biochar was taken as optimized in earlier studies . Precipitates were collected and washed.…”

“…Precipitates were collected and washed. In the stage-2 of modification, these composites were again interacted with an antioxidant solution, followed by washing and drying. , The obtained composites after stage-2 modification are denoted ASBC-I nanocomposites. Further details on nanocomposite preparation are provided in Supporting Information Section 1.3.…”

“…Biochar, derived from low-temperature pyrolysis of waste biomass, has a porous nature with vast surface functionalities. Therefore, the biochar surface holds numerous nucleation sites for the growth of RSNPs inside the pores, which limit the oxygen interaction and also prevent the aggregation of particles on the biochar surface, making it ideal for supporting RSNPs. , Biochar-supported RSNPs have been explored as adsorbents for a wide range of contaminants, including dyes, heavy metals, − radionuclides, pharmaceuticals and personal care products (PPCPs), per- and polyfluoroalkyl substances (PFAs) and other organic pollutants . Several waste biomasses have been explored as feedstock for biochar generation, and waste generated from almond and other dry fruit processing industries is one of them.…”

Efficient Removal of Hexavalent Chromium from an Aquatic System Using Nanoscale Zero-Valent Iron Supported by Ramie Biochar

“…Sewage sludge and sunflower seed shells pH = 3; Cr(VI) = 50 mg L −1 ; Dosage = 1.0 g L −1 ; Reaction time: 90 min 95.00% [17] Trametes suaveolens pH = 2; Cr(VI) = 50 mg L −1 ; Dosage = 5.0 g L −1 ; Reaction time: 90 min 100% [18] Oak wood pH = 2; Cr(VI) = 50 mg L −1 ; Dosage = 0.04 g; Reaction time: 12 h 99.9% [19] Almond shell pH = 2; Cr(VI) = 10 mg L −1 ; Dosage = 0.08 g; Reaction time: 60 min 99.8% [20] Flax straw pH = 3; Cr(VI) = 100 mg L −1 ; Dosage = 0.05 g; Reaction time: 24 h 186.99 mg/g [21] Woody biomass of Prosopis juliflora pH neutral; Cr(VI) = 10 mg L −1 ; Dosage = 0.02 g; Reaction time: 18 h 16.30 mg/g [22] Sewage sludge pH = 4; Cr(VI) = 50 mg L −1 ; Dosage = 0.05 g; Reaction time: 24 h 31.53 mg/g [23] Sewage sludge and the starch pH = 4; Cr(VI) = 30 mg L −1 ; Dosage = 1.5 g L −1 ; 98.8% [24] Rice straw pH = 4; Cr(VI) = 20 mg L −1 ; Dosage = 0.05 g; Reaction time: 24 h 40.0 mg/g; [25] Cornstalk pH = 5; Cr(VI) = 10 mg L −1 ; Dosage = 0.2 g L −1 ; Reaction time: 4 h 17.8 mg/g [6] Herb-residue pH = 2; Cr(VI) = 20 mg L −1 ; Dosage = 0.…”

Nano Geochemistry

“…Direct application of these RSNPs is challenging due to their instantaneous oxidation; therefore, researchers are continuously exploring various methods for the preservation of RSNPs, such as encapsulation in polymers, use of supporting surfaces, like clays and carbon-based materials, antioxidant capping, etc., to prevent agglomeration and preserve their redox activity [ 11 , 12 , 22 , 23 ]. Moreover, anthropogenically influenced soils and water bodies may hold multiple contaminant loads.…”