Volume 16 Issue 2

Effects of cellulase enzymatic treatment followed by mechanical beating were evaluated relative to the properties of cellulase-derived tissue pulps and handsheets. When different cellulase concentrations (0.0012 FPU/g, 0.0018 FPU/g, and 0.0024 FPU/g) of oven dried pulp (a 65/35 w/w ratio of beech to eucalyptus) were used for tissue production, a slight deterioration of the morphological characteristics was observed. Thus, a possibility of controlling the changes in the degree of polymerization of cellulose, as well as the fiber properties (in particular the length and coarseness) appeared. With an increased treatment time and enzyme concentration, these effects increased. The enzyme activity did not affect the apparent density of the paper, but the porosity drastically increased. The zero-span strength of the enzymatically treated pulps decreased with an increase in treatment time and amount of cellulase. However, mechanical beating improved the bonding between the cellulase fibers, which helped prevent the eventual decrease in mechanical properties of the handsheets. With the use of cellulase, the proposed moderate changes to fiber structure were achieved, giving the possibility of predicting and controlling the properties of tissue paper.

The present research aims to shed light on the effect of activated sludge (from a paper mill) and nanochitosan on the physical and strength properties of recycled pulp. Firstly, activated sludge was treated with 3% acetic acid for 30 min and then placed in a beaker for 90 min at 100 °C. Then, the ingredients were mixed and refined with recycled newsprint pulp in different proportions (0, 5, 10, and 15%). Finally, 2% nanochitosan was optionally added. Test specimens were prepared according to TAPPI standards with a basis weight of 120 g/m2, and their physical (water absorption) and strength (tear strength, tensile strength, burst strength, and ring crush test) properties were measured and compared. The results showed that with the increase of untreated activated sludge in recycled paper pulp, the indicators of tear resistance, ring crush test, and burst strength decreased and water absorption increased. Strength properties increased and water adsorption decreased when adding activated sludge treated with 3% acetic acid. Through the addition of nanochitosan to activated sludge treated with acetic acid, a significant increase in strength properties and a decrease in water absorption were observed.

The sol-gel method was used to make nano-TiO2 and five Chinese herbal medicines of Sophora flavescens Alt., Hypericum perforatum L., Cnidium monnieri (L.) Cuss., Kochia scoparia (L.), and Zanthoxylum bungeanum Maxim. to prepare five kinds of nano-TiO2-Chinese herbal medicine composite anti-degradative wood. Populus tomentosa Carr was chosen as the wood sample. Indoor decay resistance test results showed that the resistance to weight gain and decay of nano-TiO2-Chinese herbal medicine composite anti-degradative wood noticeably increased compared with either Chinese herbal medicine modified wood or nano-TiO2 modified wood, reaching a strong decay resistance level. The results of the anti-loss test showed that the magnitude of loss of wood samples treated with nano-TiO2 and Chinese herbal medicine was noticeably reduced compared with that with just Chinese herbal medicine. It was found by scanning electron microscopy that the nano-TiO2 particles and the Chinese herbal medicine enter the wood cell cavity, and the wood vessels and pits were the main permeation channels. Fourier transform infrared analysis results showed that nano-TiO2 could not only enter the wood interior, and associate with wood components through physical adsorption to form hydrogen bonds, but also through the carboxyl groups in cellulose and hemicellulose, or the phenolic hydroxyl group in lignin, forming a coordinated chemical bond to fix it in the wood component.

Global municipal solid waste (MSW) generation will increase to 2.2 billion tons per year by 2025 as per the World Bank projection. Improper waste management often leads to environmental degradation (i.e. water, air and soil pollution), transmission of diseases, and the release of greenhouse gases emissions, which contributes to climate change. To combat these problems, several countries are following the waste to energy (WtE) approach, which significantly reduces the volume of waste and generates renewable energy. Thus, the present study focuses on the municipal solid waste generation, composition, and waste to energy conversion technologies. Thermal conversion processes including incineration, pyrolysis, and gasification for heat, bio-oil, and syngas generation are already well established and are being employed in several countries. Currently, researchers are trying to improve the efficiency of biochemical methods such as anaerobic digestion, microbial fermentation, and microbial fuel cells for biogas, biohydrogen, and bioelectricity generation from MSW. This review explains the recent focus on microbial fermentation and microbial fuel cells for biofuels and bioelectricity production. Development of these technologies can lead to suitable eco-friendly approaches for the future. WtE technologies are important components of circular economy that will assist to achieve the demand of clean energy in future.

Cellulose is among the most promising renewable and biodegradable materials that can help meet the challenge of replacing synthetic fibers currently used in disposable N95 respirators and medical face masks. Cellulose also offers key functionalities that can be valued in filtration applications using approaches such as nanofiltration, membrane technologies, and composite structures, either through the use of nanocellulose or the design of functional composite filters. This paper presents a review of the structures and compositions of N95 respirators and medical face masks, their properties, and regulatory standards. It also reviews the use of cellulose and nanocellulose materials for mask manufacturing, along with other (nano)materials and composites that can add antimicrobial functionality to the material. A discussion of the most recent technologies providing antimicrobial properties to protective masks (by the introduction of natural bioactive compounds, metal-containing materials, metal-organic frameworks, inorganic salts, synthetic polymers, and carbon-based 2D nanomaterials) is presented. This review demonstrates that cellulose can be a solution for producing biodegradable masks from local resources in response to the high demand due to the COVID-19 pandemic and for producing antimicrobial filters to provide greater protection to the wearer and the environment, reducing cross-contamination risks during use and handling, and environmental concerns regarding disposal after use.

Biodegradable textiles made from cellulose, the most abundant biopolymer, have gained attention from researchers, due to the ease with which cellulose can be chemically modified to introduce multifunctional groups, and because of its renewable and biodegradable nature. One of the most attractive features required for civilian and military applications of textiles is flame-retardancy. This review focuses on various methods employed for the fabrication of cellulose-based flame-retardant cotton textiles along with their developed flame-retardant properties over the last few years. The most common method is to merge N, S, P, and Si-based polymeric, non-polymeric, polymeric/non-polymeric hybrids, inorganic, and organic/inorganic hybrids with cellulose to fabricate flame-retardant cotton textiles. In these studies, cellulose was chemically bonded with the flame-retardants or in some cases, cotton textiles were coated by flame-retardants. The flame-retardant properties of the cotton textiles were investigated and determined by various methods, including the limiting oxygen index (LOI), the vertical flame test, thermal gravimetric analysis (TGA), and by cone calorimetry. This review demonstrates the potential of cellulose-based flame-retardant textiles for various applications.

Despite the extraordinary properties of nanocellulose (NC), as confirmed through two decades of exhaustive research, addressing an array of potential applications, the NC market is still far from reaching its full potential. Among the main causes is the lack of process-adapted measuring tools capable of characterizing NC, at acceptable speed and reliability, to meet the industrial demands in a cost-effective way. Therefore, reliable characterization methodologies of NC and new standards are of paramount importance in ensuring reproducible research results and quality control specifications for present and future NC products and applications. Furthermore, the successful industrial use of NC products depends on critical parameters that are still being identified and studied. This review paper aims to identify some of the current drawbacks and limitations in NC characterization that hinder their commercial deployment. Moreover, important challenges related to characterization and new opportunities for future research in this field are addressed.

Bio-based ethylene produced by bioethanol dehydration is an environmentally friendly substitute for oil-based ethylene. It is a low-pollution raw material that can be used to produce high-value bio-based materials. Currently, some industrial plants use first-generation (1G) bioethanol to produce bio-ethylene. However, second-generation (2G) bioethanol is not currently used to produce bio-ethylene because the manufacturing processes are not optimized. The conversion of lignocellulosic biomass to bio-ethylene involves pretreatment, enzymatic hydrolysis of carbohydrates, the fermentation of sugars to ethanol, ethanol recovery by distillation, and ethanol dehydration to ethylene. This work presents a review of second-generation (2G) bio-ethylene production, analyzing the stages of the process, possible derivatives, uses, and applications. This review also contains technical, economic, and environmental considerations in the possible installation of a biorefinery in the northeast region of Argentina (NEA).

Native cellulose is mainly found in phytomass, such as trees and other plants. It has a regular hierarchical nanoarchitecture, in which the extended macromolecular chains are aligned and closely packed in parallel to form the crystalline nanofibrils of cell walls. In the context of material utilization, nanocellulose is a collective term for nano-ordered assemblies of cellulose chains. In recent times, it has been produced in large quantities from woody bioresources. In addition, nanocellulose has some fascinating physicochemical properties, such as high strength, light weight, transparency, birefringence, and low thermal expansion. These properties have enabled broad functional design of nanocellulose-based materials; but most of them are facing serious competition from various products that already exist. However, nanocellulose is not just a green alternative to existing materials. Rather, it is expected to make a profound difference in terms of pioneering novel functions. The present review focuses on the unexpected features of nanocellulose materials, triggered by details of the inherent nanoarchitecture of native cellulose.

The agricultural industry is one of the main economic contributors in developing countries, especially in tropical regions. Extensive land clearing has led to severe erosion within the watersheds, which increases the vulnerability of water catchments to natural disasters, such as floods. Cellulosic fibers, such as jute, sisal, kenaf, hemp, and coir, are gaining increasing worldwide attention for their potential application in controlling soil erosion, principally due to their remarkable biodegradable and physical properties. Nonetheless, the research on biocomposites in controlling soil erosion is limited compared to the natural fibers. This is perhaps due to poor availability and high cost of biodegradable polymers compared to natural fibers, which are abundant and inexpensive. Poor adhesive interactions between the matrix and natural fibers due to the hydrophilic characteristic of the fibers is another major drawback that limits the development of biocomposites for controlling soil erosion.