Sustainable management of tea wastes: resource recovery and conversion techniques.

As the demand for tea (Camellia sinensis) has grown across the world, the amount of biomass waste that has been produced during the harvesting process has also increased. Tea consumption was estimated at about 6.3 million tonnes in 2020 and is anticipated to reach 7.4 million tonnes by 2025. The generation of tea waste (TW) after use has also increased concurrently with rising tea consumption. TW includes clipped stems, wasted tea leaves, and buds. Many TW-derived products have proven benefits in various applications, including energy generation, energy storage, wastewater treatment, and pharmaceuticals. TW is widely used in environmental and energy-related applications. Energy recovery from low- and medium-calorific value fuels may be accomplished in a highly efficient manner using pyrolysis, anaerobic digestion, and gasification. TW-made biochar and activated carbon are also promising adsorbents for use in environmental applications. Another area where TW shows promise is in the synthesis of phytochemicals. This review offers an overview of the conversion procedures for TW into value-added products. Further, the improvements in their applications for energy generation, energy storage, removal of different contaminants, and extraction of phytochemicals have been reviewed. A comprehensive assessment of the sustainable use of TWs as environmentally acceptable renewable resources is compiled in this review.

Microwave-assisted quick synthesis of microcrystalline cellulose from black tea waste (Camellia sinensis) and characterization.

Tea wastes generated in the industries during tea production processes show excellent potential to be used as a renewable, abundant, and cheap source for the extraction of microcrystalline cellulose. In the current work, MCC was isolated from black tea waste through microwave heating instead of using conventional heating and avoiding the traditional acid hydrolysis method. Microwave increased the reaction speed significantly and resulted in very quick delignification and bleaching of black tea waste to isolate MCC in white powdered form. FTIR, XRD, FESEM, and TGA analysis were then carried out to investigate the chemical functionality, crystallinity, morphology, and thermal properties, respectively, of the synthesized tea waste MCC. The characterization results demonstrated that cellulose with a short rough fibrous structure having an average particle size of around 23.06 µm was extracted. The results of FTIR and XRD demonstrated unequivocally that all amorphous non-cellulosic compounds had been eliminated. The microwave-extracted black tea waste MCC showed 89.77 % crystallinity and good thermal properties, indicating that it could be a promising filler material for preparing polymer composites. Therefore, microwave-assisted delignification and bleaching can be used as a suitable, energy-efficient, time-saving and low-cost method for extracting MCC from the black tea waste produced in tea factories.

Synthesis of lignin from waste leaves and its potential application for bread packaging: A waste valorization approach.

In this study, lignin was synthesized from the waste leaves of Ficus auriculata obtained after the extraction of gallic acid. The synthesized lignin was incorporated into PVA films, and the neat and blended films were characterized using different techniques. Lignin addition improved the UV-shielding, thermal, antioxidant, and mechanical properties of PVA films. The water solubility decreased from 31.86 % to 7.14 ± 1.94 %, while the water vapor permeability increased from 3.85 ± 0.21 × 10-7 g.m.h-1 Pa-1 to 7.84 ± 0.64 × 10-7 g.m.h-1 Pa-1 for pure PVA film and the film containing 5 % lignin, respectively. The prepared films showed a much better performance than commercial packaging films in inhibiting mold growth during the storage of preservative-free bread. The bread samples packed with commercial packaging showed signs of mold growth on the 3rd day, while the growth was inhibited entirely till the 15th day for PVA film containing 1 % lignin. The pure PVA film and the ones containing 3 % and 5 % of lignin inhibited growth till the 12th and 9th day, respectively. Findings from the current study show that safe, cheap, and eco-friendly biomaterials can hinder the growth of spoilage microorganisms and potentially be used in food packaging.

Antioxidant-Incorporated Poly(vinyl alcohol) Coating: Preparation, Characterization, and Influence on Ripening of Green Bananas.

In this study, the gallic acid (antioxidant)-rich leaf extract of Ficus auriculata was incorporated into poly(vinyl alcohol) (PVA) and utilized as a coating to delay the ripening of green bananas. The films exhibited low opacity of 0.86 ± 0.014 for pure PVA (PP) and 0.92 ± 0.019, 0.99 ± 0.020, and 1.18 ± 0.029 for PVA + 1% extract (PE1), PVA + 5% extract (PE5), and PVA + 10% extract (PE10), respectively, indicating excellent transparency. The weight loss was higher in the uncoated group than in any coated fruits. The reduction in titratable acidity and the increase in total soluble sugars were slower in all of the coated samples as compared to the uncoated ones. The fruits without any treatment attained complete maturity on the ninth day where the ion leakage was 85.61 ± 2.33% while that of PP was 56.36 ± 2.95% and those of PE1, PE5, and PE10 remained below 30%. The coated samples showed better retention and consequently slower degradation of chlorophyll. The fruits coated with pure PVA as well as 10% extract-incorporated PVA remained acceptable till day 15, while the ones with 1 and 5% of extract reached full ripeness on day 18. Results of the present investigation suggest that safe, low-cost, and environmentally friendly coatings can improve the shelf life of perishable produces like bananas.

Sugarcane bagasse into value-added products: a review.

Strategic valorization of readily available sugarcane bagasse (SB) is very important for waste management and sustainable biorefinery. Conventional SB pretreatment methods are ineffective to meet the requirement for industrial adaptation. Several past studies have highlighted different pretreatment procedures which are lacking environmentally benign characteristics and effective SB bioconversion. This article provides an in-depth review of a variety of environmentally acceptable thermochemical and biological pretreatment techniques for SB. Advancements in the conversion processes such as pyrolysis, liquefaction, gasification, cogeneration, lignin conversion, and cellulose conversion via fermentation processes are critically reviewed for the formation of an extensive array of industrially relevant products such as biofuels, bioelectricity, bioplastics, bio adsorbents, and organic acids. This article would provide comprehensive insights into several crucial aspects of thermochemical and biological conversion processes, including systematic perceptions and scientific developments for value-added products from SB valorization. Moreover, it would lead to determining efficient pretreatment and/or conversion processes for sustainable development of industrial-scale sugarcane-based biorefinery.

Environmental remediation by tea waste and its derivative products: A review on present status and technological advancements.

The rising consumption of the popular non-alcoholic beverage tea and its derivative products caused massive growth in worldwide tea production in the last decade, leading to the generation of huge quantities of waste tea residues every year. Most of these wastes are usually burnt or disposed in landfills without proper treatment which results in serious environmental issues by polluting water, air and soil. In the recent times, 'waste to wealth' is a fast-growing concept for environment friendly sustainable development. Utilization of the large amount of tea wastes for the production of low-cost adsorbents to reduce the expenses of water and wastewater treatment can be a sustainable way of management of these wastes which at the same time will improve circular economy also. This review endeavours to evaluate the potential of both raw and modified tea wastes towards the adsorption of pollutants from wastewater. The production of various adsorptive materials such as biochar, activated carbon, nanocomposites, hydrogels, nanoparticles from tea wastes are summarized. The advancements in their applications for the removal of different emerging contaminants from wastewater as well as potable water, air and soil are exhaustively reviewed. The outcome of the present review reveals that tea waste and its derivatives are appropriate candidates to be used as adsorbents that show tremendous effectiveness in cleaning the environment. This article will provide the readers with an in-depth knowledge on the sustainable utilization of tea waste as adsorbent materials and will assist them to explore this abundant cheap waste biomass for environmental remediation.

A review on global perspectives of sustainable development in bioenergy generation.

Over the last few decades, the globe has much relied on fossil fuels; however, environmental concerns forced the World to look at biofuel as an alternative for stable economic development. Biofuel also facilitates national energy security maintenance and reduces environmental complications. The present study is focused on an in-depth analysis of bioenergy policy measures undertaken by various federal agencies of different countries in order to shed light on the bottlenecks that impede biofuel's growth as a sustainable and alternative fuel. An in-depth assessment of feedstock utilization, blending targets, and policy assistance schemes have been thoroughly reviewed. In addition, the potential of commercial firms for the production of bioenergy is highlighted in order to grasp the current bioenergy market scenario better. Finally, the article is concluded with the viewpoints of the authors to address the standing issues of global bioenergy generation.

A critical review on the techniques used for the synthesis and applications of crystalline cellulose derived from agricultural wastes and forest residues.

In order to meet the growing energy crisis of the 21st century, the utilization of bio-based materials has become a field of high research endeavour. In view of that, the present review paper is focused on different techniques that are frequently explored for the synthesis of value-added crystalline derivatives of cellulose like MCC and NCC from agricultural wastes and forest residues. Moreover, a comparative analysis between thermochemical and biochemical methods is carried out for such valorization of biomass considering the mechanism involved with various reactions. Further, a critical analysis is performed on various individual techniques specifically used for the applications of MCC and NCC in different fields including environmental, polymer industry, pharmaceutical and other emerging sectors. This article will assist the readers not only to explore new biomass sources but also provides an in-depth insight on various green and cost-effective methods for sustainable production of crystalline cellulose.

A review on the environment-friendly emerging techniques for pretreatment of lignocellulosic biomass: Mechanistic insight and advancements.

The process of pretreatment is considered as an indispensable unit operation in the field of lignocellulosic conversion. The traditional pretreatment operations of lignocellulosic biomass are observed as inefficient to meet the demand for an industrial adaptation. In view of that, numerous investigations are reported on various conventional pretreatment methods but very limited information's are available on the advanced technologies. The present review article provides an exclusive discussion on various emerging and environment-friendly pretreatment methods applied on a number of different feedstock materials. Further, an insight on the reaction mechanism involved with each of the technologies such as microwave, ultrasound, deep eutectic solvent, irradiation, and high force assisted pretreatment methods are elucidated for an effective valorization of lignocellulosic biomass. Hence, in a single article, the readers of this paper will get to know all important aspects of the emerging pretreatment techniques of lignocellulosic biomass including the advancements, and the mechanistic insight which will be highly beneficial towards the selection of an efficient pretreatment method for large scale of commercial implementation in a lignocellulosic biorefinery.

Micro and nanocrystalline cellulose derivatives of lignocellulosic biomass: A review on synthesis, applications and advancements.

The present review article is focused on the progress in different aspects of synthesis, modification and advanced applications of both of microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC). First of all, the potential of lignocellulosic biomass towards the formation of MCC and NCC was discussed. Further, different routes for the extraction of the derivatives are individually explained based on the mechanism involved in the formation of MCC and NCC. Moreover, the phenomenon of surface modification was highlighted in order to improve the functionality of the materials. Thereafter, the emerging and advanced applications of both of MCC and NCC are explored in different fields. Finally, the paper is concluded with the challenges that are frequently encountered during the process of commercial production of MCC and NCC. This paper will be beneficial to the readers for acquiring all the important aspects of both of MCC and NCC together in a single article.

Technological advancement in the synthesis and applications of lignin-based nanoparticles derived from agro-industrial waste residues: A review.

Over the years, lignin has drawn a great deal of interest for their potential use as bio-polymers due to the presence of high amount of phenolic compounds, non-polluting feature and cost-competitiveness as compared to synthetic polymers. However, in order to fast-track their development, different attempts are made towards the usage of lignin in nano form since it exhibits some unique properties in nanoscale range. The present review article provides a detail analysis on the recent advancement in the synthesis and applications of lignin nanoparticles (LNPs) derived from agro-industrial waste residues. In view of that, an in-depth morphological analysis was reviewed to assess the structural influence on the characteristics of LNPs. Further, application of LNPs is explored in different fields including bio-medical engineering, pharmaceuticals, skin-care products and food industries. Finally, the paper is concluded discussing various challenges associated with the synthesis, modification and development with an aspiration of futuristic developments. The readers of this review article will be highly benefitted after acquiring a comprehensive knowledge on LNPs and its different synthesis processes along with various applications.

Green synthesis and environmental application of iron-based nanomaterials and nanocomposite: A review.

Green chemistry has been proven to be an efficient route for nanoparticle synthesis. Plant extract based green synthesis of various nanoparticles is extensively studied since the last decade. This paper "Green synthesis and environmental application of Iron-based nanomaterials and nanocomposite: A review" unveils all the possible greener techniques for the synthesis of iron-based nanoparticles and nanocomposites. The use of different plant sources, microorganisms, and various biocompatible green reagents such as biopolymers, cellulose, haemoglobin, and glucose for the synthesis of iron nanoparticles reported in the last decade are summarized. The microwave method, along with hydrothermal synthesis due to their lower energy consumption are also been referred to as a green route. Apart from different plant parts, waste leaves and roots used for the synthesis of iron nanoparticles are extensively briefed here. This review is thus compact in nature which covers all the broad areas of green synthesis of iron nanoparticles (NPs) and iron-based nanocomposites. Detailed discussion on environmental applications of the various green synthesized iron NPs and their composites with performance efficiency is provided in this review article. The advantages of bimetallic iron-based nanocomposites over iron NPs in various environmental applications are discussed in detail. The hazards and toxic properties of green synthesized iron-based NPs are compared with those obtained from chemical methods. The prospects and challenges section of this article provides a vivid outlook of adapting such useful technique into a more versatile process with certain inclusions which may encourage and provide a new direction to future research.

Recent Developments in Nanomaterials-Modified Membranes for Improved Membrane Distillation Performance.

Membrane distillation (MD) is a thermally induced membrane separation process that utilizes vapor pressure variance to permeate the more volatile constituent, typically water as vapor, across a hydrophobic membrane and rejects the less volatile components of the feed. Permeate flux decline, membrane fouling, and wetting are some serious challenges faced in MD operations. Thus, in recent years, various studies have been carried out on the modification of these MD membranes by incorporating nanomaterials to overcome these challenges and significantly improve the performance of these membranes. This review provides a comprehensive evaluation of the incorporation of new generation nanomaterials such as quantum dots, metalloids and metal oxide-based nanoparticles, metal organic frameworks (MOFs), and carbon-based nanomaterials in the MD membrane. The desired characteristics of the membrane for MD operations, such as a higher liquid entry pressure (LEPw), permeability, porosity, hydrophobicity, chemical stability, thermal conductivity, and mechanical strength, have been thoroughly discussed. Additionally, methodologies adopted for the incorporation of nanomaterials in these membranes, including surface grafting, plasma polymerization, interfacial polymerization, dip coating, and the efficacy of these modified membranes in various MD operations along with their applications are addressed. Further, the current challenges in modifying MD membranes using nanomaterials along with prominent future aspects have been systematically elaborated.

Loading and release of doxorubicin hydrochloride from iron(iii) trimesate MOF and zinc oxide nanoparticle composites.

A significant amount of work has been done in recent years for the development of metal organic framework (MOF) based drug delivery vehicles. Often, nanomaterials such as iron oxide (Fe3O4), zinc oxide (ZnO), and other metal oxides like graphene oxide etc. are incorporated into the structures to impart additional functionality. In this work, an iron(iii) trimesate metal organic framework i.e. MIL-100(Fe) and its composites with ZnO nanoparticles i.e. ZnO@MIL-100(Fe) were investigated as delivery agents for anticancer drug doxorubicin hydrochloride (DOX). The synthesis of the composites was done by two routes viz. a conventional HF route (in the presence of HF as a crystallizing agent) and another one in the absence of HF. The resultant MOF and its composites significantly differ in DOX loading capacity and release rates. The results obtained in this work indicate that the DOX loading capacity increases upon addition of nanoparticles when the original MOF has lower mesopore volume (as in the sample obtained via the HF route). Surprisingly, this increase in the DOX loading was comparable to that of Fe3O4@MIL-100(Fe), although the two pure nanoparticles (ZnO and Fe3O4) have widely different loading capacities. On the other hand, the addition of ZnO nanoparticles reduces the DOX loading capacity, if the MOF has higher mesopore volume (as for the sample obtained via the HF free route). The composites synthesized by the HF route with enhanced loading capacity exhibit slower DOX release rates due to the stronger interaction of the drug with the composite.

MOFs for the treatment of arsenic, fluoride and iron contaminated drinking water: A review.

Over the last few decades, the global pollution of surface and groundwater poses a serious threat not only to human beings but also towards aquatic lives due to the presence of emerging contaminants. Among the others, the presence of arsenic, fluoride, and iron are considered as the most common toxic pollutants in water bodies. The emergence of metal organic frameworks (MOFs) with high porosity and surface area is represented as significant inclusion into the era of entrapping contaminants present in drinking water. In the present review article, an in-depth insight is provided on the recent developments in the removal of arsenic, fluoride, and iron from drinking water using MOFs. Various aspects related to the synthesis, latest technologies adopted for the modifications in the synthesis process and advanced applications of MOFs for the removal of such contaminants are explicitly discussed. A detailed insight was provided to understand the mechanism of various interactions of MOFs with arsenic and fluoride. With respect to arsenic, fluoride, and iron removal the ultrastructural morphology of MOFs is assessed based on different molecular arrangements. Further, commercial aspects of various MOFs are presented in order to highlight the process feasibility. Finally, various perspectives and challenges involved in process scale up are comprehensively narrated with an aspiration of futuristic developments. The paper will be beneficial to the readers for acquiring a piece of in-depth knowledge on MOFs and its various synthesis approaches along with remarkable achievements for the removal of arsenic, fluoride, and iron from contaminated drinking water.

Preparation and characterization of novel green synthesized iron-aluminum nanocomposite and studying its efficiency in fluoride removal.

A novel green synthesized iron-aluminum nanocomposite was prepared and characterized by FESEM, FTIR, EDX, XRD, BET, DSC and TGA analysis. The clove extract acting as both reducing and surface coating agent was optimized based on its maximum total flavonoid content (TFC) and total polyphenolic content (TPC). Fluoride adsorption studies was performed at 298K, 303K and 313K within the range of 10-40 mg/L fluoride solution for kinetic and isotherm studies. Maximum adsorption capacity of 42.95 mg/g was obtained for 0.25 g/L adsorbent dosage. Moreover fluoride adsorption obeyed pseudo second order kinetic model whereas the process was multistage diffusion controlled. Langmuir isotherm model best fitted the equilibrium data with monolayer adsorption capacities of 25.09, 26.08 and 28.07 mg/g at 298, 303 and 313K respectively. The findings confirmed that the fluoride adsorption process followed ion exchange mechanism with the surface hydroxyl groups. The prepared nanocomposite was utilized for treating fluoride contaminated water samples from north-east regions of India which showed efficient removal percentage.

Preparation and characterization of animal bone powder impregnated fly ash catalyst for transesterification.

The present work reconnoitres the feasibility of utilizing class F fly ash and calcined animal bone powder (CABP) as raw material for the synthesis of heterogeneous solid base catalyst with varying ratios (CABP of 10, 20, and 30 mass%), that is subsequently used for transesterification of mustard oil. Physicochemical characterization of CABP revealed crystalline behavior, signifying one of the components as hydroxyapatite (HAP); when calcined at 900 °C transforms to ß-tricalcium phosphate having a specific surface area of 100 m2 g-1. The synthesized catalyst showed improved catalytic activity when compared to the parental species and the optimal value to achieve the highest conversion of 90.4% would be at CABP loading of 10 mass%, 5.5:1 methanol to oil molar ratio, and 10 mass% catalyst concentration for 6 h. The prepared biodiesel had a calorific value of 36.2 MJ kg-1 with ash content < 0.01 mass%. The catalyst could be reused five times with no loss in its activity. Results indicated that calcium enriched waste materials when impregnated in fly ash might be a potential source of catalyst in biodiesel production.

House hold unit for the treatment of fluoride, iron, arsenic and microorganism contaminated drinking water.

A first of its kind hybrid electrocoagulation-filtration prototype unit was fabricated for the removal of fluoride, iron, arsenic and microorganisms contaminated drinking water. The unit comprised of 3 chambers, chamber A consisting of an inlet for the water to be treated and an outlet for the treated water along with one block of aluminum electrodes. Chamber B consisted of ceramic membrane filtration assembly at the bottom over a metallic support which filters the flocs so produced in chamber A and chamber C consisting of space to collect the treated water. Operating parameters were maintained as current density of 625 A m-2 and an electrode distance of 0.005 m. Contaminated drinking water containing mixture of fluoride (10 mg L-1), iron (25 mg L-1), arsenic (200 µg L-1) and microorganisms (35 CFU ml-1) was used for the experiment. A removal of 98.74%, 95.65%, 93.2% and 100% were obtained for iron, arsenic, fluoride and microorganisms, respectively. The apparatus and method made it possible to efficiently treat contaminated drinking water to produce drinkable water as per WHO specification. By-products obtained from the electrocoagulation bath were analyzed using SEM, EDX and XRD and explained.

Novel synthesis of nanocomposite for the extraction of Sildenafil Citrate (Viagra) from water and urine samples: Process screening and optimization.

A sensitive analytical method is investigated to concentrate and determine trace level of Sildenafil Citrate (SLC) present in water and urine samples. The method is based on a sample treatment using dispersive solid-phase micro-extraction (DSPME) with laboratory-made Mn@ CuS/ZnS nanocomposite loaded on activated carbon (Mn@ CuS/ZnS-NCs-AC) as a sorbent for the target analyte. The efficiency was enhanced by ultrasound-assisted (UA) with dispersive nanocomposite solid-phase micro-extraction (UA-DNSPME). Four significant variables affecting SLC recovery like; pH, eluent volume, sonication time and adsorbent mass were selected by the Plackett-Burman design (PBD) experiments. These selected factors were optimized by the central composite design (CCD) to maximize extraction of SLC. The results exhibited that the optimum conditions for maximizing extraction of SLC were 6.0 pH, 300µL eluent (acetonitrile) volume, 10mg of adsorbent and 6min sonication time. Under optimized conditions, virtuous linearity of SLC was ranged from 30 to 4000ngmL-1 with R2 of 0.99. The limit of detection (LOD) was 2.50ngmL-1 and the recoveries at two spiked levels were ranged from 97.37 to 103.21% with the relative standard deviation (RSD) less than 4.50% (n=15). The enhancement factor (EF) was 81.91. The results show that the combination UAE with DNSPME is a suitable method for the determination of SLC in water and urine samples.

Ultrasonic assisted dispersive solid-phase microextraction of Eriochrome Cyanine R from water sample on ultrasonically synthesized lead (II) dioxide nanoparticles loaded on activated carbon: Experimental design methodology.

The present research focus on designing an appropriate dispersive solid-phase microextraction (UA-DSPME) for preconcentration and determination of Eriochrome Cyanine R (ECR) in aqueous solutions with aid of sonication using lead (II) dioxide nanoparticles loaded on activated carbon (PbO-NPs-AC). This material was fully identified with XRD and SEM. Influence of pH, amounts of sorbent, type and volume of eluent, and sonication time on response properties were investigated and optimized by central composite design (CCD) combined with surface response methodology using STATISTICA. Among different solvents, dimethyl sulfoxide (DMSO) was selected as an efficient eluent, which its combination by present nanoparticles and application of ultrasound waves led to enhancement in mass transfer. The predicted maximum extraction (100%) under the optimum conditions of the process variables viz. pH 4.5, eluent 200µL, adsorbent dosage 2.5mg and 5min sonication was close to the experimental value (99.50%). at optimum conditions some experimental features like wide 5-2000ngmL-1 ECR, low detection limit (0.43ngmL-1, S/N=3:1) and good repeatability and reproducibility (relative standard deviation, <5.5%, n=12) indicate versatility in successful applicability of present method for real sample analysis. Investigation of accuracy by spiking known concentration of ECR over 200-600ngmL-1 gave mean recoveries from 94.850% to 101.42% under optimal conditions. The procedure was also applied for the pre-concentration and subsequent determination of ECR in tap and waste waters.