In Situ Synthesis of Zero-Valent Iron-Decorated Lignite Carbon for Aqueous Heavy Metal Remediation

Abstract

Lignite’s large abundance, physicochemical properties and low cost are attractive for industrial wastewater remediation. However, directly applying lignite for wastewater treatment suffers low efficiency. Here, we synthesize highly efficient zero-valent iron (ZVI)-decorated lignite carbon through the in-situ carbonization of a lignite and FeCl2 mixture for heavy metal removal. The effect of carbonization temperature on the morphology, structure and crystallite phases of ZVI-decorated lignite carbons (ZVI-LXs) was investigated. At an optimized temperature (i.e., 1000 °C), ZVI particles were found evenly distributed on the lignite matrix with the particles between 20 to 190 nm. Moreover, ZVI particles were protected by a graphene shell that was formed in situ during the carbonization. The synthesized ZVI-L1000 exhibited higher Cu2+, Pb2+ and Cd2+ stripping capacities than pristine lignite in a wide pH range of 2.2–6.3 due to the surface-deposited ZVI particles. The maximum Langmuir adsorption capacities of ZVI-L1000 for Cd2+, Pb2+ and Cu2+ were 38.3, 55.2 and 42.5 mg/g at 25 °C, respectively, which were 7.8, 4.5 and 10.6 times greater than that of pristine lignite, respectively. ZVI-L1000 also exhibited a fast metal removal speed (~15 min), which is ideal for industrial wastewater treatment. The pseudo-second-order model fits well with all three adsorptions, indicating that chemical forces control their rate-limiting adsorption steps. The reduction mechanisms of ZVI-L1000 for heavy metals include reduction, precipitation and complexation.

Cobalt/Iron Bimetallic Biochar Composites for Lead(II) Adsorption: Mechanism and Remediation Performance

“…The FTIR spectra of BC@Co/Fe-5 before and after Pb 2+ adsorption are shown in Figure 7a. For BC@Co/Fe-5 before Pb 2+ adsorption, the strong, wide absorption peak at 3440.49 cm −1 corresponds to the stretching vibration of O-H [44], the absorption peak at 1625.77 cm −1 corresponds to the asymmetric stretching vibration of COO [44], the absorption peaks at 1571.03 and 1549.02 cm −1 are attributed to the vibration of the benzene ring skeleton [45], the absorption peak at 1118.05 cm −1 is attributed to the C-O-C stretching vibration [44], and the absorption peak at 565.17 cm −1 corresponds to the stretching vibration of Fe-O [44]. The Fe-O absorption peak appears because BC@Co/Fe-5 is oxidised to form ferrite during grinding.…”

“…29, x FOR PEER REVIEW 8 of 18 skeleton[45], the absorption peak at 1118.05 cm −1 is attributed to the C-O-C stretching vibration[44], and the absorption peak at 565.17 cm −1 corresponds to the stretching vibration of Fe-O[44]. The Fe-O absorption peak appears because BC@Co/Fe-5 is oxidised to form ferrite during grinding.…”

Sustainable phosphate removal using Mg/Ca-biochar hybrids: Current trends and future outlooks

“…Currently, biochar is widely used in energy (Malyan et al, 2021), carbon capture (Dissanayake et al, 2022), stormwater monitoring (Ulrich et al, 2015), soil conditioning (Shen and Yuan, 2021), and waste management (Behera and Samal, 2022) as it is carbon-neutral, easily accessible, reduced cost, and easy amendability . Moreover, the porous structure, functional groups and minerals in biochar facilitate the adsorption (Samaraweera et al, 2023). Biochar exhibits a large surface area and porosity when biomass/waste is slow-or fast-pyrolyzed at higher temperatures, promoting organic and inorganic contaminant removal from wastewater (Samaraweera et al, 2021b).…”

Peptides Used for Heavy Metal Remediation: A Promising Approach

“…They can also remove a variety of organic and heavy metal pollutants [ 37 , 38 ]. Nano-scale zero-valent iron (nZVI) is one of the most studied materials for environmental purification [ 39 , 40 ]. It has a small particle size, a large specific surface area, strong adsorption and reduction abilities, high activity, and high pollution reduction ability [ 41 ].…”