Lignocellulosic biomass waste is a cheap, eco-friendly, and sustainable raw material for a wide array of applications. In the present study, an easy, fast, and economically feasible route has been proposed for the preparation of different zero-valent metal nanoparticles (ZV-MNPs) based on Cu, Co, Ag, and Ni NPs using empty fruit bunch (EFB) biomass residue as support material. The catalytic efficiency of ZV-MNPs/EFB catalyst was investigated against five model pollutants, such as methyl orange (MO), congo red (CR), methylene blue (MB), acridine orange (AO), and 4-nitrophenol (4-NP) using NaBH4 as a source of hydrogen and electron. Comparative study revealed that among as-prepared ZV-MNPs/EFB catalysts, Cu-NPs immobilized onto EFB (Cu/EFB) exhibited maximum catalytic efficiency towards pollutant abasement. Degradation reactions were highly efficient, and were completed within a short time (4 min) in case of MO, CR, and MB, whilst AO and 4-NP were reduced in less than 15 min. Kinetic investigation revealed that the degradation rate of model pollutants accorded with pseudo-first order model. Furthermore, supported catalysts were easily recovered after the completion of experiment by simply pulling the catalyst from reaction system. Recyclability tests performed on Cu/EFB revealed that more than 97% of the reduction was achieved in case of MO dye for four successive cycles of reuse. The as-prepared heterostructure showed multifunctional properties, such as enhanced uptake of contaminants, high catalytic efficiency, and easy recovery, hence, offers great prospects in wastewater purification.
The development of marine algae-derived oil sorbents is an emerging field with potential to offer a promising solution to mitigate catastrophic impact of oil spills. Herein, a highly buoyant, hydrophobic and magnetically separable oil sorbent "calcium stearate-modified magnetic activated carbon" (CS@MAC) was fabricated by anchoring magnetite over algal biocarbon derived from Rhizoclonium hookeri and by subsequent surface coating with calcium stearate. Characterization studies using FTIR, SEM, XRD, and TG evidenced that surface modifications of algal biomass were effective in bringing concomitant changes in its properties, rendering it suitable for oil spill clean-up applications. SEM results verified even distribution of magnetite spheres (~50 nm) over biocarbon's surface, and the presence of CS in the resultant sorbent was established by FTIR and TG, which leads to buoyancy and hydrophobicity. Our engineered CS@MAC demonstrated excellent oil sequestration efficiency exceeding 90% and fast kinetics (30 min) using a low dose in synthetic sea water matrices. Compared with magnetic biochar and magnetic activated carbon, the CS@MAC not only reached up to a higher oil uptake efficiency but also remained buoyant, validating its suitability for oil spill clean-up. Furthermore, CS@MAC demonstrated robust performance with removal efficiency of 93% in 1st to 74% in 5th cycle, indicating its potential for practical applications. These combined findings show that our designed sorbent is an eco-friendly, affordable, and buoyant material with improved hydrophobicity, signifying a viable solution for facile oil spill clean-up.
In this work, facile fabrication of lignin nanoparticles (LNP)-based three-dimensional reduced graphene oxide hydrogel (rGO@LNP) has been demonstrated as a novel strategy for environmental applications. Herein, LNP were facilely synthesized from walnut shell waste through a direct chemical route. These LNP were incorporated into the continuous porous network of rGO network to fabricate rGO@LNP hydrogel. Characterization studies were carried out using various analytical techniques viz. scanning electron microscopy, Fourier transform IR spectroscopy, X-ray diffraction and thermogravimetric analysis. The efficiency of rGO@LNP hydrogel as adsorptive platform was evaluated by employing methylene blue and Pb2+ as model pollutants, whilst the effect of various experimental parameters was ascertained for optimal performance. Furthermore, Agar well diffusion method was used to check the antibacterial activities of the hydrogel using two bacterial pathogenic strains, i.e. Klebsiella pneumoniae (gram negative) and Enterococcus faecalis (gram positive). Results showed that after the inclusion of LNP into rGO hydrogel, there was a marked improvement in pollutant's uptake ability and compared to bare LNP and rGO, the composite hydrogel showed enhanced bactericidal effect. Overall, this approach is outstanding because of the synergy of functional properties of nano-lignin and rGO due to multi-interaction sites in the resulting hydrogel. The results presented herein support the application of rGO@LNP as innovative water filter material for scavenging broad spectrum pollutants and bactericidal properties.
The present study suggests a scalable approach to fabricate a composite hydrogel based on cerium dioxide (CeO2) nanoparticles anchored onto microcrystalline cellulose (MCC) in a three-dimensional reduced graphene oxide (rGO) hydrogel with bifunctional performances in water reclamation. Herein, CeO2 nanoparticles were biosynthesized using Banana pseudo-stem extract as a stabilizer and reducing agent. Afterwards, a series of hierarchical scaffolds of 3D hydrogels were fabricated employing different contents of CeO2, MCC and rGO via. self-assembly process. Analytical techniques provided useful insights regarding chemical structure and morphology of the fabricated hydrogel. Results showed that the proportion of CeO2, MCC and rGO controlled performance characteristics of the resulting composite hydrogels. Under optimal condition, 95 % of the catalytic reduction of methylene blue dye solution (50 ppm) was achieved rapidly in the presence of catalyst (20 mg) using NaBH4 solution (0.25 M) at ambient temperature. Recyclability tests demonstrated long term stability of composite hydrogel all through four successive cycles without any significant loss of its effectiveness. Moreover, as-prepared hydrogels demonstrated appreciable antibacterial potential against Gram-positive and Gram-negative bacteria. It is evident that using MCC and rGO as supporting substrates with CeO2 NPs accorded more functions to the resulting composite hydrogel due to synergistic effects that resulted in a high performance, easily retrieving and steady material for wastewater purification.