Approach For Valorization Research Articles

Efficient Electrocatalytic Hydrodechlorination and Detoxification of Chlorophenols by Palladium-Palladium Oxide Heterostructure.

Electrocatalytic hydrodechlorination is a promising approach for simultaneous pollutant purification and valorization. However, the lack of electrocatalysts with high catalytic activity and selectivity limits its application. Here, we propose a palladium-palladium oxide (Pd-PdO) heterostructure for efficient electrocatalytic hydrodechlorination of recalcitrant chlorophenols and selective formation of phenol with superior Pd-mass activity (1.35 min-1 mgPd-1), which is 4.4 times of commercial Pd/C and about 10-100 times of reported Pd-based catalysts. The Pd-PdO heterostructure is stable in real water matrices and achieves selective phenol recovery (>99%) from the chlorophenol mixture and efficient detoxification along chlorophenol removal. Experimental results and computational modeling reveal that the adsorption/desorption behaviors of zerovalent Pd and PdO sites in the Pd-PdO heterostructure are optimized and a synergy is realized to promote atomic hydrogen (H*) generation, transfer, and utilization: H* is efficiently generated at zerovalent Pd sites, transferred to PdO sites, and eventually consumed in the dechlorination reaction at PdO sites. This work provides a promising strategy to realize the synergy of Pd with different valence states in the metal-metal oxide heterostructure for simultaneous decontamination, detoxification, and resource recovery from halogenated organic pollutants.

Co-pyrolysis of plastic waste and macroalgae Ulva lactuca, a sustainable valorization approach towards the production of bio-oil and biochar

To address the pressing demand for sustainable energy in light of environmental challenges, this study explored the synergetic effects of the co-pyrolysis of polyethylene terephthalate (PET) and Ulva lactuca macroalgae to yield bio-oil and biochar. The objective is to enhance the bio-oil quality for wider usability and to combat marine pollution. By employing co-pyrolysis, notable progress has been achieved in bio-oil yield and quality, particularly in hydrocarbon content, through the integration of PET. The highest bio-oil yield of 37.91 % was achieved under optimal conditions at 500 °C with a feedstock mixture consisting of 40 % U. lactuca and 60 % PET. Under these conditions, the bio-oil exhibited a significant increase in hydrocarbon content, reaching 57.16 %, which is essential for improving its energy potential. Biochar quality was also enhanced, with the biochar from a 70 % U. lactuca and 30 % PET blend showing a BET surface area of 20.18 m2/g, compared to the initial 1.38 m2/g of raw U. lactuca, indicating improved surface properties. This study presents a sustainable energy generation and environmental preservation approach, underscoring the potential of synergistically utilizing marine resources and plastic waste.

The treatment of acid mine drainage (AMD) using a combination of selective precipitation and bio-sorption techniques: A hybrid and stepwise approach for AMD valorization and environmental pollution control

In this study, selective precipitation using magnesium oxide (MgO) and bio-sorption with banana peels (BPs) were explored for the treatment and valorization of acid mine drainage (AMD). The treatment chain comprised two distinct stages of which selective precipitation of chemical species using MgO (step1) and polishing of pre-treated AMD using BPs (step 2). In stage 1, 2.0 L of AMD from coal mine were used for selective precipitation and recovery of chemical species using MgO. The results revealed that chemical species of concern were precipitated and recovered at different pH gradients with Fe(III) precipitated at pH ≤ 4, Al at pH ≥ 4-5, Fe(II), Mn and Zn at pH ≥ 8 while Ca and SO42─ were precipitated throughout the pH range. In stage 2, the pre-treated AMD water was polished using BPs. The results revealed an overall increase of pH from 1.7 to 10, and substantial removal of chemical species in the following removal efficiency: Al, Cu and Zn (100% each), ≥ Fe and Mn (99.99% each), ≥ Ni (99.93%), and ≥ SO42─ (90%). The chemical treatment step removed pollutants partially, whereas the bio-sorption step acted as a polishing stage by removing residual pollutants.

Recovery of pure PET from wool/PET/elastane textile waste through step-wise enzymatic and chemical processing

Textile waste is mostly incinerated because few recycling processes are available to recover valuable materials. In this work, a feasible chemo-enzymatic recycling process of wool/polyethylene terephthalate (PET)/elastane blends to recover pure PET is for the first time successfully demonstrated. Two novel enzyme formulations were selected for wool hydrolysis, whereas the recovered amino acids were quantified using high-performance liquid chromatography and two assays (Ninhydrin and Folin–Ciocalteu). Kinetic studies on the amino acid formation alongside reaction observations by scanning electron microscopy proved sufficient removal of wool within 8 hours with the new enzyme formulation, marking an acceleration compared to previous studies. Finally, elastane was separated with a non-hazardous solvent to obtain pure PET. Tensile tests on the recovered PET fibres reveal only slight changes through the enzymatic treatment and no changes induced by the applied solvent. The enzyme formulation was successfully tested on five different post-consumer wool/PET textile waste samples. This valorization approach enhances the circular economy concept for textile waste recycling.

Sustainable valorization of waste plastic into nanostructured materials for environmental, energy, catalytic and biomedical applications: A review

The extensive production and utilization of plastic products are inevitable in the current scenario. However, the non-degradable nature of waste plastic generated after use poses a grave concern. Comprehensive efforts are being made to find viable technological solutions to manage the escalating challenge of waste plastic. This review focuses on the progress made in transformation of waste plastic into value-added nanomaterials. An overview is provided of the waste plastic issue on a global level and its ecological impacts. Currently established methodologies for waste plastic management are examined, along with their limitations. Subsequently, state-of-the-art techniques for converting waste plastic into nanostructured materials are presented, with a critical evaluation of their distinct merits and demerits. Several demonstrated technologies and case studies are discussed regarding the utilization of these nanomaterials in diverse applications, including environmental remediation, energy production and storage, catalytic processes, sensors, drug delivery, bioimaging, regenerative medicine and advanced packaging materials. Moreover, challenges and prospects in the commercial level production of waste plastic-derived nanomaterials and their adoption for industrial and practical usage are highlighted. Overall, this work underscores the potential of transforming waste plastic into nanostructured materials for multifaceted applications. The valorization approach presented here offers an integration of waste plastic management and sustainable nanotechnology. The development of such technologies should pave the way toward a circular economy and the attainment of sustainable development goals.

Impact of nickel and alkaline earth metals interaction on sustainable carbon nanotubes generation from plastic face masks via catalytic pyrolysis

The one-pot synthesis of carbon nanotubes (CNTs) emerges as a promising approach for plastic valorization, owing to its simplicity and scalability. However, limited attention has been given to catalyst design for this method, particularly regarding the influence of Group 2 alkaline earth metal elements (X) on the Ni-based catalyst activity. This study investigates the impact of X on the catalytic activity of Ni towards sustainable CNTs synthesis using plastic face masks. The findings revealed that X influenced the carbon yield of NiMo-X catalysts and the morphology of the resultant carbon nanomaterials. Notably, NiMo-Ca demonstrated the highest carbon yield, whereas NiMo-Mg and NiMo-Ba exhibited the lowest. Furthermore, NiMo-Mg tends to produce clean and thin CNTs, while NiMo-Ba tends to yield carbon flakes with numerous irregular cokes. In addition to the effect of Ni crystallite size, which influences the transition from tubular to flake-like carbon structures, environmental factors are also considered. Specifically, NiMo-Mg generated a high CO2/CH4 environment, while NiMo-Ba exhibited slower catalytic cracking of polymeric chains from face masks, both of which were unfavorable for CNTs growth. Conversely, NiMo-Ca facilitated higher carbon recovery, likely due to its creation of a low CO2/CH4 environment via CO2 methanation. Optimization studies indicated that increasing pyrolysis temperatures and durations lead to reduced carbon yield, while cyclic pyrolysis of face masks up to five iterations enhances the reusability of NiMo-X catalysts with improved carbon recovery. Overall, this study provides valuable insights into the early pyrolytic gas formation and carbon nucleation phase, which are influenced by the surface Ni fraction and Ni polarization, as well as the later CNTs growth phase, which is related to the Ni crystallite size.

Green valorization approach of Citrus limetta peels by ultrasound-assisted enzymatic extraction for recovery of dietary fibers: Optimization, physicochemical, structural, functional, and thermal properties

Green valorization approach of Citrus limetta peels by ultrasound-assisted enzymatic extraction for recovery of dietary fibers: Optimization, physicochemical, structural, functional, and thermal properties

Sulfonated graphitic carbon catalyst derived from coffee waste: A sustainable valorization approach for highly efficient production of 5-hydroxymethylfurfural (5-HMF) from fructose

According to recent research, a sulfonated 2D graphitic carbon catalyst for the dehydration of fructose to the platform chemical 5-Hydroxymethylfurfural (5-HMF) can be made from used ground coffee. By carbonizing and activating at different temperatures, sulfonated graphitic carbon (SC) catalysts with varied chemical compositions and textural characteristics were obtained. The physical and chemical characteristics of the SC catalysts were assessed using XRD, Raman, SEM-EDX, HR-TEM, BET analysis, and XPS. Due to its microporous structure, SC-900 exhibited a high specific area and demonstrated selective and efficient production of 5-HMF from fructose. All in all, the surface acidity of catalysts was measured by NH3-TPD, and acid-base titration methods. The SC-900 catalyst, designed through carbonization at 900 ℃, achieved a fructose conversion rate of 100 % and a 5-HMF yield of 97.91 % without generating any by-products. This indicates the catalyst essentially produces 5-HMF under the specified optimal conditions (140 ℃, 90 min) observed in this study. To determine the origins of the highly efficient and highly selective conversion of fructose to 5-HMF, the performance of the SC catalysts was systematically investigated vi-a-vis their physical and chemical properties. The development of microporous SC catalysts and their application as catalysts not only enhances the value of waste coffee but also provides an environmentally friendly approach for converting carbohydrates into 5-HMF.

CeO2-Supported Single-Atom Cu Catalysts Modified with Fe for RWGS Reaction: Deciphering the Role of Fe in the Reaction Mechanism by In Situ/Operando Spectroscopic Techniques.

Reverse water-gas shift (RWGS) reaction has attracted much attention as a potential approach for CO2 valorization via the production of synthesis gas, especially over Fe-modified supported Cu catalysts on CeO2. However, most studies have focused solely on investigating the RWGS reaction over catalysts with high Cu and Fe loadings, thus leading to an increase in the complexity of the catalytic system and, hence, preventing the gain of any reliable information about the nature of the active sites and reaction mechanism. In this work, a CeO2-supported single-atom Cu catalyst modified with iron was synthesized and evaluated for the RWGS reaction. The catalytic results reveal a significant synergistic effect between CuCeO2 and Fe, demonstrating an activity up to three times higher than the combined catalytic activities of monometallic catalysts (Fe/CeO2 + CuCeO2) under identical conditions. Various ex situ and in situ/operando techniques are employed to unveil the concealed role of Fe in catalyst activity enhancement. The combined findings from hydrogen temperature-programmed reduction (H2-TPR) and operando electron paramagnetic resonance spectroscopy (EPR) reveal that the added Fe predominantly interacts with Cu-containing surface sites, resulting in the stabilization of higher proportions of Cu single sites. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and operando EPR results unveil a synergistic interplay of Fe with Cu-containing sites and CeO x domains, efficiently enhancing both the reoxidation of Cu+ in Cu+-Ov-Ce3+ moieties and the reducibility of Ce4+ in CeO x domains under RWGS conditions. Detailed mechanistic studies reveal that the RWGS reaction predominantly proceeds via the redox mechanism.

Enzymatic hydrolysis of waste streams originating from wastewater treatment plants

BackgroundAchieving climate neutrality is a goal that calls for action in all sectors. The requirements for improving waste management and reducing carbon emissions from the energy sector present an opportunity for wastewater treatment plants (WWTPs) to introduce sustainable waste treatment practices. A common biotechnological approach for waste valorization is the production of sugars from lignocellulosic waste biomass via biological hydrolysis. WWTPs produce waste streams such as sewage sludge and screenings which have not yet been fully explored as feedstocks for sugar production yet are promising because of their carbohydrate content and the lack of lignin structures. This study aims to explore the enzymatic hydrolysis of various waste streams originating from WWTPs by using a laboratory-made and a commercial cellulolytic enzyme cocktail for the production of sugars. Additionally, the impact of lipid and protein recovery from sewage sludge prior to the hydrolysis was assessed.ResultsTreatment with a laboratory-made enzyme cocktail produced by Irpex lacteus (IL) produced 31.2 mg sugar per g dry wastewater screenings. A commercial enzyme formulation released 101 mg sugar per g dry screenings, corresponding to 90% degree of saccharification. There was an increase in sugar levels for all sewage substrates during the hydrolysis with IL enzyme. Lipid and protein recovery from primary and secondary sludge prior to the hydrolysis with IL enzyme was not advantageous in terms of sugar production.ConclusionsThe laboratory-made fungal IL enzyme showed its versatility and possible application beyond the typical lignocellulosic biomass. Wastewater screenings are well suited for valorization through sugar production by enzymatic hydrolysis. Saccharification of screenings represents a viable strategy to divert this waste stream from landfill and achieve the waste treatment and renewable energy targets set by the European Union. The investigation of lipid and protein recovery from sewage sludge showed the challenges of integrating resource recovery and saccharification processes.

Mapping the Sustainability of Waste-to-Energy Processes for Food Loss and Waste in Mexico—Part 1: Energy Feasibility Study

Mexico generated 8.9 Mt of food loss and waste (FLW) at food distribution and retail centers in the year 2022. Traditional management methods in Latin America primarily involve final disposal sites, contributing to national greenhouse gas emissions of 0.22 Mt CO2 eq y−1. This creates an urgent need for sustainable valorization strategies for FLW to mitigate environmental impacts. This comprehensive study analyzes the geographical distribution of FLW generation and proposes a valorization approach using WtE-AD plants. Geographic information systems were employed for geographical analysis, life cycle assessment was used for environmental evaluation, and circular economy business models were applied for sustainability assessment. The primary objective of this first part of the contribution is to evaluate the technical feasibility of implementing waste-to-energy anaerobic digestion (WtE-AD) plants for FLW management in Mexico considering their geographical locations. The results demonstrate that WtE-AD plants with treatment capacities exceeding 8 t d−1 can achieve positive energy balances and significantly reduce greenhouse gas emissions. Specific findings indicate that these plants are viable for large-scale implementation, with larger plants showing resilience to increased transport distances while maintaining energy efficiency. The results highlight the critical influence of methane yields and transport distances on plant energy performance. This study underscores the importance of strategically placing and scaling WtE-AD plants to optimize resource efficiency and environmental sustainability. These findings provide essential insights for policymakers and stakeholders advocating for the transition of Mexico’s food supply chain toward a circular economy. Future parts of this study will explore detailed economic analyses and the policy frameworks necessary for the large-scale implementation of WtE-AD plants in Mexico. Further research should continue to develop innovative strategies to enhance the techno-economic and environmental performance of WtE-AD processes, ensuring sustainable FLW management and energy recovery.

Recovery and Characterization of Calcium-Rich Mineral Powders Obtained from Fish and Shrimp Waste: A Smart Valorization of Waste to Treasure

With the increase in global aquaculture production, managing waste from aquatic biomass has become a significant concern. This research aimed to develop a sustainable valorization approach for recovering calcium-rich fish, including mackerel tuna and pangas bone and shrimp shell powders. The powders were characterized by various physicochemical and nutritional parameters, including proximate composition, amino acids, protein solubility, water holding capacity (WHC), oil holding capacity (OHC), and heavy metal contents. Color analysis and structural examination were carried out using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FT-IR), and in vitro radical scavenging activity was assessed. Significant protein content was observed in the powders, which was highest in shrimp shell powder (SSP) at 37.78%, followed by 32.29% in pangas bone powder (PBP) and 30.28% in tuna bone powder (TBP). The ash content was consistent in PBP and TBP at around 62.80%, while SSP had a lower ash content of 36.58%. Amino acid analysis detected 14 different amino acids in the recovered powders. Notably, SSP demonstrated the highest WHC and OHC values (2.90 and 2.81, respectively), whereas TBP exhibited the lowest values (1.11 for WHC and 1.21 for OHC). FE-SEM revealed the compact structure of TBP and PBP, contrasting with the porous surface of SSP. EDX analysis indicated higher calcium (24.52%) and phosphorus (13.85%) contents in TBP, while SSP was enriched in carbon (54.54%). All detected heavy metal concentrations were within acceptable limits. The recovered powders demonstrated significant ABTS free radical scavenging activity. The findings of this study suggest the suitability of the recovered powders for various food and pharmaceutical applications.

Enhanced anaerobic digestion of food waste using purified lactonic sophorolipids produced by solid-state fermentation of molasses and oil waste: A circular approach

In the present work, the effect of pure lactonic sophorolipids (SL) on the anaerobic digestion of biowaste was investigated. For this purpose, crude SL were produced from organic waste (a mixture of molasses and winterization oil cake) through solid-state fermentation (SSF) in a 22L pilot-scale aerobic bioreactor using the yeast Starmerella bombicola as SL-producing microorganism. The crude material extracted from the SSF exhaust solid contained several forms of SL and it was purified using High-Performance Liquid Chromatography (HPLC) and characterized by means of Liquid Chromatography-Mass Spectrometry (LC-MS) yielding a high-purity C18 lactonic SL (>99%). This pure SL was used to enhance the batch anaerobic digestion of source-selected biowaste, mainly composed by kitchen waste. The best dosage of SL was in the range of 0.02–0.04 g SL/g TS, with an increment of methane yield of 41% in NmL/g VS. The presence of SL did not significantly alter the structure of the microbial community or general biodiversity. In summary, we propose a circular approach for waste valorisation in which different organic waste streams are combined in a biorefinery-like configuration, where the solid-state fermentation is used to produce SL and results in an enhanced bioenergy production.

Synergistic enzyme assisted release of ferulic acid from brewer´s spent grain

Brewer’s spent grain (BSG), the most abundant by-product of the beer industry, can be considered a sustainable source of ferulic acid (4-hydroxy-3-methoxycinnamic acid) (FA). FA is esterified to the arabinoxylan in the BSG. FA exhibits a variety of biological activities and is a target for valorization of BSG. We present a novel enzyme-assisted approach that utilizes the synergistic action of a specific bacterial endo-1,4-β-xylanase and a fungal ferulic acid esterase activity to selectively release high yields of FA from BSG. The study compares the efficacy of three different fungal feruloyl esterases (E.C. 3.1.1.73) of carbohydrate esterase family 1 (CE1), HiFae, AoFae1, and AnFae1, acting separately or in combination with two different endo-1,4-β-xylanases (EC 3.2.1.8), a bacterial GH30 enzyme from Dickeya chrysanthemi, and Shearzyme®, a commercial GH10 enzyme from Aspergillus aculeatus, respectively. On an equimolar dosage basis, the AnFae1-GH30 was the most efficient combination in releasing FA from BSG. This combination showed significant synergy in a dose-dependent manner, enabling up to 85% FA recovery from BSG within 30 min. of treatment. The results demonstrate a novel enzymatic approach for valorization of BSG as FA is considered a high-value natural compound for use in e.g. anti-aging skin care products.

Valorization of Chlorella Microalgae Residual Biomass via Catalytic Acid Hydrolysis/Dehydration and Hydrogenolysis/Hydrogenation

Microalgal biomass can be utilized for the production of value-added chemicals and fuels. Within this research, Chlorella vulgaris biomass left behind after the extraction of lipids and proteins was converted to valuable sugars, organic acids and furanic compounds via hydrolysis/dehydration using dilute aqueous sulfuric acid as a homogeneous catalyst. Under mild conditions, i.e., low temperature and low sulfuric acid concentration, the main products of hydrolysis/dehydration were monomeric sugars (glucose and xylose) and furanic compounds (HMF, furfural) while under more intense conditions (i.e., higher temperature and higher acid concentration), organic acids (propionic, formic, acetic, succinic, lactic, levulinic) were also produced either directly from sugar conversion or via intermediate furans. As a second valorization approach, the residual microalgal biomass was converted to value-added sugar alcohols (sorbitol, glycerol) via hydrogenation/hydrogenolysis reactions over metallic ruthenium catalysts supported on activated carbons (5%Ru/C). It was also shown that a low concentration of sulfuric acid facilitated the conversion of biomass to sugar alcohols by initiating the hydrolysis of carbohydrates to monomeric sugars. Overall, this work aims to propose valorization pathways for a rarely utilized residual biomass towards useful compounds utilized as platform chemicals and precursors for the production of a wide variety of solvents, polymers, fuels, food ingredients, pharmaceuticals and others.

Optimization of operating conditions for lampante olive oil deacidification by short path molecular distillation: Waste valorization approach

Short path molecular distillation (SPMD) is an advanced distillation eco-friendly technique performed under high vacuum with vast applications in food processing, including vegetable oils physical refining. In this research, lampante olive oil, as a low-grade byproduct of olive oil producing companies, with high free fatty acids (FFA) content of 10.11 (wt % as oleic acid) was deacidified using SPMD. Optimization of SPMD was carried out using Box-Behnken response surface methodology (RSM-BB). Three important operating factors including evaporation temperature (150–200 °C), feed flow rate (0.50–3.00 mL/min), and feed temperature (50–100 °C) were selected to evaluate the SPMD process. At the best separation conditions of 195 °C, 0.5 mL/min, and 50 °C, the FFA content, deacidification efficiency (DE) and polar compounds (PC) were determined as 1.42 wt %, 85.95 % and 8.2 wt % respectively. Furthermore, SPMD efficiency was compared to some conventional methods including fractional distillation (FD), steam stripping distillation (SSD) and alkali neutralization (AN). In addition, the impact of FFA content on SPMD process was examined. It was concluded that SPMD could effectively and sustainably deacidify lampante olive oil to a reasonable extent and could facilitate the physical refining as a valorization process.

Synthesis and characterization of composite films derived from lemongrass leaves: A valorization approach

Over the past few decades, research into more ecologically friendly packaging materials has significantly increased to reduce non-renewable plastic usage. In this context, biobased films were synthesized from extracted lemongrass leaves. An integrated pretreatment of conventional alkali followed by deep eutectic solvents (DES) was utilized to fractionate the lemongrass leaves into three usable forms, i.e., hemicellulose (HC), lignin (L), and cellulose, which were further utilized in the synthesis of composite films. A total of 4 films have been synthesized, labelled as: Film 1 (CMC HC), Film 2 (L HC), Film 3 (CMC L), and Film 4 (CMC HC L). Film 4 has shown a good water absorption capacity of nearly 65 % and also a higher contact angle of 99.90°, while film 2 has the highest thermal stability among all the films. Film 3 has better UV properties due to the presence of carboxymethyl cellulose (CMC) and lignin. Statement of noveltyIn the present work, composite films have been synthesized from lemongrass leaves for the first time. This is the first report that synthesizes the films from extracted components (CMC, lignin, and hemicellulose) of lemongrass leaves. In this study, all the components were extracted via sequential conventional alkali and DES pretreatment. After extraction, these components were utilized for the composite film synthesis, which is used for various applications of their desirable properties.

In situ patterning of nickel/sulfur-codoped laser-induced graphene electrode for selective electrocatalytic valorization of glycerol

The electrocatalytic valorization of glycerol is an emerging upcycling process for the biomass utilization. In this work, nickel/sulfur-codoped laser-induced graphene (LINiSG) on flexible polyimide film was fabricated and demonstrated as a self-supported and binder-free monolithic electrode for electrocatalytic glycerol oxidation reaction (EGOR) towards the selective generation of value-added three-carbon (C3) chemicals. The laser-induced in-situ and synchronous carbonization of polysulfone and Ni precursor was demonstrated to remarkably promote both the electrochemical surface area and Ni loading of LINiSG electrode. These synergistic merits are considered as the main origin for its enhanced EGOR activity and stability, showing much smaller Tafel slope and 2-fold enhanced current density, as compared to LINiG electrode without the co-carbonization of polysulfone. The influence of experimental parameters has been systematically investigated by the product analysis, achieving an average 94.7 % C3 selectivity and 76.1 % C3 Faradaic efficiency with a high selectivity of dihydroxyacetone (ca. 67.7 %) in near-neutral conditions, which is better than most of the reported EGOR electrodes operated in near-neutral conditions. This work demonstrated the viability of using flexible self-supported and binder-free LIG electrode with rational design and preparation approach for electrocatalytic valorization of biomass.

High extraction and excellent anti-UV and anti-oxidant proprieties of lignin from Reseda Luteola L. waste by organosolv process

Lignin is an abundant natural biopolymer found in plant cell walls. Lignin can come from tinctorial plants, whose residual biomass after dye extraction was typically discarded as waste. The main objective of this study was to extract lignin from the residual biomass of Reseda luteola L. using an organosolv process and to optimize the extraction conditions. The extracted lignin was characterized, and its potential applications as an antimicrobial, anti-oxidant, and anti-UV agent were investigated. Response surface methodology based on a Box-Behnken design was employed to optimize the lignin extraction conditions (organic acid concentration, material-to-liquid ratio, extraction time). The extracted lignin was comprehensively characterized using NMR, FTIR, XRD, SEM-EDX, TGA, DSC, and UV–Vis techniques. The optimal extraction conditions yielded a remarkably high lignin recovery of 62.41 % from the plant waste, which was rarely achieved for non-wood plants in previous works. The extracted lignin exhibited excellent thermal stability and radical scavenging anti-oxidant activity but no significant antimicrobial effects. Treating wool fabrics with lignin nanoparticles substantially enhanced UV protection from the “good” to “excellent” category based on the UPF rating. This sustainable valorization approach converted abundant tinctorial plant waste into high-purity lignin with promising anti-oxidant and UV-blocking properties suitable for various applications.

Evaluation of ZnO nanoparticles from ‘Monsooned Malabar Robusta Coffee’ husk as a potential antioxidant and biocidal candidate: A sustainable valorization approach

Nanotechnology has become a sustainable strategy to combat drug resistance. As agro-waste management has become a concern, efficient management of produced waste has been an imposing global issue. This study evaluated antioxidant, as well as antibacterial and antibiofilm potential of zinc oxide nanoparticles (ZnO NPs) synthesized by hydrothermal approach using ethanolic extract of ‘Monsooned Malabar Robusta coffee’ husk against multi-drug-resistant (MDR) strains of enteroaggregative Escherichia coli, Salmonella Enteritidis, S. Typhimurium and methicillin-resistant Staphylococcus aureus. The fabrication of ZnO NPs was confirmed by spectroscopy, whereas thermogravimetric analysis-differential thermogravimetric analysis confirmed stability of ZnO NPs, while the X-ray diffraction pattern confirmed the wurtzite crystalline structure. The agglomerated nature of ZnO NPs with a nearly spherical shape was evident with scanning electron microscopy, whereas transmission electron microscopy revealed a poly-crystalline nature with a mean diameter of 26.33 ± 3.778 nm. The microbroth dilution technique revealed a minimum inhibitory concentration (MIC) of 250 μg/mL and a minimum bactericidal concentration (MBC) of 500 μg/mL for the ZnO NPs. Furthermore, ZnO NPs exhibited significant antibiofilm activity against the MDR-test strains. Moreover, ZnO NPs were tested safe at MIC and MBC doses in chicken erythrocytes, and commensal gut microflora tested were not inhibited. Besides, a dose-dependent antioxidant property was exhibited by ZnO NPs. Additionally, in vitro time-kill kinetic assay of MDR-test strains treated with ZnO NPs revealed a complete bacterial clearance at 24 h. Overall, the synthesis of ZnO NPs from coffee husk demonstrated a simple, eco-friendly and valorization approach that could be devised as a potential delivery molecule.