Adsorption of dyes from water by Prunella vulgaris stem and subsequent fungal decolorization

Enhancing bacterial biodegradation of n-hexane by utilizing the adsorption capacity of non-degrading fungi

Biodegradation of hydrophobic volatile organic compounds (VOCs) such as n-hexane is limited by their poor accessibility. Constructing fungal-bacterial degradation alliances is an effective approach, but the role of those fungi without the capability to degrade VOCs may have been overlooked. In this study, a non-n-hexane-degrading fungus, Fusarium keratoplasticum FK, was utilized to enhance n-hexane degradation by the bacterium Mycobacterium neworleansense WCJ. It was shown that strain WCJ removed 64.84% of n-hexane (at a concentration of 648.20 mg L-1) over 3 d, and 84.04% after introducing strain FK. Microbial growth kinetic studies revealed that the growth of strain WCJ was also promoted. Through a stepwise adsorption-degradation experiment combined with qPCR technology, it was found that the strain WCJ could utilize the n-hexane pre-adsorbed by strain FK, with an increase in copy number from 108.2662 to 108.7731. Therefore, the non-degrading fungi can improved the accessibility of n-hexane by providing n-hexane adsorbed by the mycelium to the degrading bacteria. In addition, the adsorption tests and characterization of the fungal samples before and after Soxhlet extraction indicated that the adsorption of n-hexane on strain FK conformed to Lagergren's pseudo-second-order kinetics and Freundlich adsorption isotherms, and was correlated with the presence of lipids and nonpolar groups. This study emphasizes the potential role of non-degrading fungi in bioremediation and proposes a viable strategy to enhance the bacterial degradation of hydrophobic VOCs.

Novel synthesis of multicomponent porous nano-hybrid composite, theoretical investigation using DFT and dye adsorption applications: disposing of waste with waste

Extensive studies have shown that doping can enhance the properties of graphene, but the application to real industrial wastewater treatment and theoretical calculations are limited. In this study, the hybrid nanoadsorbent Cu, N co-doped graphene (Cu@NG) was successfully synthesized via green route using carbon rods from waste dry batteries, human urine and copper nitrate, then multiple characterizations, detailed density functional theory (DFT) theoretical calculations and comprehensive actual wastewater tests are performed in environmental applications to investigate the adsorption properties and mechanism. The results showed that Cu@NG surface is mesoporous, decorated with CuO crystals and doped with N atoms. The isotherms and kinetics were simulated by Langmuir and pseudo-second-order models, respectively. The theoretical maximum sorption for MB and CV on Cu@NG is 116.28 mg·g^-1 and CV is 86.96 mg·g^-1, respectively. Pilot tests with Cu@NG on real textile wastewater showed that COD, BOD and color were removed by 54.2%, 55.2% and 86.4%, respectively. The desorption rate of Cu@NG is approximately above 90% for both MB and CV on Cu@NG after six cycles of treatment. The DFT calculations confirmed the experimental results as MB is more reactive than CV molecules. Besides, interactions have been systematically investigated via topology and natural bond orbital (NBO) analyses. The process mechanism involved mainly electrostatic adsorption, π-π stacking interactions and H-bonding interactions and ion exchange.

Recent advances in biopolymer-based advanced oxidation processes for dye removal applications: A review

Over the past few years, synthetic dye-contaminated wastewater has attracted considerable global attention due to the low biodegradability and the ability of organic dyes to persist and remain toxic, causing numerous health and environmental concerns. As a result of the recalcitrant nature of those complex organic dyes, the remediation of wastewater using conventional wastewater treatment techniques is becoming increasingly challenging. In recent years, advanced oxidation processes (AOPs) have emerged as a potential alternative to treat organic dyestuffs discharged from industries. The most widely employed AOPs include photocatalysis, ozonation, Fenton oxidation, electrochemical oxidation, catalytic heterogeneous oxidation, and ultrasound irradiation. These processes involve the generation of highly reactive radicals to oxidize organic dyes into innocuous minerals. However, many conventional AOPs suffer from several setbacks, including the high cost, high consumption of reagents and substrates, self-agglomeration of catalysts, limited reusability, and the requirement of light, ultrasound, or electricity. Therefore, there has been significant interest in improving the performance of conventional AOPs using biopolymers and heterogeneous catalysts such as metal oxide nanoparticles (MONPs). Biopolymers have been widely considered in developing green, sustainable, eco-friendly, and low-cost AOP-based dye removal technologies. They inherit intriguing properties like biodegradability, renewability, nontoxicity, relative abundance, and sorption. In addition, the immobilization of catalysts on biopolymer supports has been proven to possess excellent catalytic activity and turnover numbers. The current review provides comprehensive coverage of different AOPs and how efficiently biopolymers, including cellulose, chitin, chitosan, alginate, gelatin, guar gum, keratin, silk fibroin, zein, albumin, lignin, and starch, have been integrated with heterogeneous AOPs in dye removal applications. This review also discusses the general degradation mechanisms of AOPs, applications of biopolymers in AOPs and the roles of biopolymers in AOPs-based dye removal processes. Furthermore, key challenges and future perspectives of biopolymer-based AOPs have also been highlighted.

Synthesis of Starch-Grafted Polymethyl Methacrylate via Free Radical Polymerization Reaction and Its Application for the Uptake of Methylene Blue

In this research, a new biodegradable and eco-friendly adsorbent, starch-grafted polymethyl methacrylate (St-g-PMMA) was synthesized. The St-g-PMMA was synthesized by a free radical polymerization reaction in which methyl methacrylate (MMA) was grafted onto a starch polymer chain. The reaction was performed in water in the presence of a potassium persulfate (KPS) initiator. The structure and different properties of the St-g-PMMA was explored by FT-IR, 1H NMR, TGA, SEM and XRD. After characterization, the St-g-PMMA was used for the removal of MB dye. Different adsorption parameters, such as effect of adsorbent dose, effect of pH, effect of initial concentration of dye solution, effect of contact time and comparative adsorption study were investigated. The St-g-PMMA showed a maximum removal percentage (R%) of 97% towards MB. The other parameters, such as the isothermal and kinetic models, were fitted to the experimental data. The results showed that the Langmuir adsorption and pseudo second order kinetic models were best fitted to experimental data with a regression coefficient of R² = 0.93 and 0.99, respectively.

Adsorption of anionic dyes from textile wastewater utilizing raw corncob

Toxic dyes are irrefutable effluent components of textile wastewater, so they have become a major economic and health concern. With the purpose of efficient removal of textile dyes, multiple nature-inspired adsorbents have been applied. Herein, raw corncob is proposed as a novel highly efficient, low-price, and abundantly attainable adsorbent with the potential for uptake of methyl red and methyl orange. Multiple experiments were carried out to optimize parameters including pH, primary concentration, adsorbent dosage, temperature, and contact time. The adsorption was raised with the mounting of the contact time and it was alleviated with the addition of initial concentration. The foremost uptake of dye was apperceived at an acidic medium pH 4 for methyl red and pH 1 for methyl orange. Scanning Electron Microscopy and Fourier Transform Infrared Spectroscopy were employed to characterize the surfaces of corncobs. The well-fitted Langmuir and Freundlich models (methyl red: R² = 0.9956 and methyl orange: R² = 0.9883) confirmed the homogeneous monolayer adsorption process on the raw corncob surface. The obtained results disclose that corncob is an effectual biosorbent for eliminating anionic dyes without the necessity for any prior modifications.