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One of the most important environmental issues in the world today is the problem of air pollution, which includes particulate matter (PM) and greenhouse gases (mainly CO 2 ). The production of efficient sustainable filters to overcome this concern as well as to provide an alternative to synthetic petroleum-based filters remains a demanding challenge. The purpose of this research was to first produce novel cellulose nanofibers (CNF) based nanofilter from a combination of CNF and chitosan (CS) and then evaluate its applicability for air purification. A number of structural and chemical properties as well as CO 2 and PM adsorption efficiency of the modified CNF, were determined using advanced characterization techniques. After pretests, we determined the optimum loading for the CS was 1 wt%, and upon producing the samples, the CNF loadings (1, 1.5, and 2 wt%) were chosen as one variable. For particle absorption, the PM sizes (0.1, 0.3, 0.5, and 2.5 μm) were kept as other variables. Based on SEM results, we concluded the higher the concentration of CNF the higher the specific surface area and the lower the porosity and the diameter of the pores, which was confirmed by the BET test. Furthermore, the results showed that increasing the concentration of modified CNFs increases the adsorption rate of CO 2 and PM and that the highest adsorption of CO 2 and PM belonged to the 2% modified CNF., (Copyright © 2021. Published by Elsevier B.V.)

Filtration is a promising water treatment method to purify drinking water. To develop highly efficient drinking water filter paper, water-resistant cellulose foam paper with a high wet strength property was fabricated using diverse metal oxide (e.g., copper oxide (CuO), zinc oxide (ZnO), and silver oxide (Ag 2 O)) nanoparticles. These nanoparticles were synthesized using the hydrothermal reaction method. Their morphological structures were studied using a field emission scanning electron microscope (FESEM). The presence of coated nanoparticles on the cellulose foam filter was verified by energy dispersive X-ray spectroscopy (EDX) methods. The antibacterial performance of different types of modified cellulose foam filters was studied against E. coli, P. aeruginosa, B. subtilis, and B. cereus strains using the zone of inhibition test. The antibacterial profile of the cellulose foam filter impregnated with Ag 2 O nanoparticles, when tested against different types of bacteria, exhibited higher antibacterial activity than the cellulose foam filter impregnated with ZnO and CuO nanoparticles., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Volatile organic compounds (VOCs) are significant atmospheric pollutants that cause environmental and health risks. Waste gases polluted with multiple VOCs often need to be purified simultaneously in biofilters, which may lead to antagonistic, neutral, or synergistic effects on removal performance. Antagonism limits the application of biofilters to simultaneous treatment of multiple VOCs, while synergism has not yet been fully exploited. We review the interactions among multiple target pollutants and the changes in the bioavailability and biodegradability of substrates that are responsible for substrate interactions. Potential strategies for enhancing biofilter performance are then discussed. Finally, we propose further efforts to alleviate antagonism by enhancing bioavailability and biodegradability, and discuss possible challenges to take advantage of synergism., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Development of a foam-formed cellulose filter paper with high wet strength was carried out for application as a drinking water filter. The wet strength and antimicrobial activity of cellulose foam paper against several bacteria species (Bacillus subtilis MTCC 441 (Gram +ve), B. cereus NCDC 240 (Gram +ve), Pseudomonas aeruginosa NCDC 105 (Gram -ve), Klebsiella pneumonia NCDC 138 (Gram -ve), and Escherichia coli MTCC 40 (Gram -ve)) were investigated. The morphology and structure of the cellulose foam paper were characterized using scanning electron microscopy (SEM). The results of our study confirmed that glutaraldehyde solution or 1,2,3,4-butanetetracarboxylic acid (BTCA) added to cellulose foam paper pretreated with cationic polyacrylamide (C-PAM) provided very high and stable wet strength performance together with excellent antimicrobial properties., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Synthetic filters are neither biodegradable nor produced from renewable sources. Thus, their disposal has serious environmental impacts. There is a growing desire to produce filters from cellulosic fibers that are renewable, biodegradable, cheap and most importantly recyclable if the contamination is removed. Foam-laid process in papermaking is a promising process for the production of specialty papers. Filters produced using this process are capable of providing products with high specific surface area and tortuous structure favorable for entrapping particulate matters, while providing excellent permeability for incoming gas or liquid. Although the end product fulfills completely the requirement of a filter in a dry environment, it fails completely if it is exposed to a moist environment. This work reports on converting the hydrophilic cellulosic filter into a hydrophobic product without disturbing its original structure.

Saccharides and lignin components in prehydrolysis liquor (PHL) from kraft-based dissolving pulp production was characterized after being fractionated using membrane filtration. The results showed that the membrane filtration provided a method for organics fractionation with considerable recovery rate, but exhibited some disadvantages. Besides the limited ability in purifying oligosaccharides (OS) due to the overlaps of molecular weight distribution with lignin components, the membrane filtration could not improve the homogeneity of OS as indicated by the analysis of chemical compositions and the degree of polymerization (DP), which may be ascribed to the linear conformation of OS. The characterization of lignin components indicated a great potential for polymer industry because of the remarkable content of phenolic hydroxyl groups (PhOH), especially for low molecular weight (LMW) fraction. It was concluded the organics in PHL provided streams of value-added chemicals. However, the practical significance thereof can be realized and maximized only when they are successfully and completely fractionated., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

In this work, laccase treatment was employed to enhance nanofiltration process by lignin removal. Results showed that the membrane filterability was increased in terms of deionized water flux and PHL filtration process. On the other hand, the hemicellulosic sugars were negligible affected and can be concentrated to 172 g/L, which was increased about 300% from the original one. The combined laccase-nanofiltration process provides an alternative approach to utilize hemicellulosic sugars of PHL in an environmentally friendly way., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Paper-based biosensors represent a disruptive technology by providing instantaneous and low-cost diagnostics for health and environmental applications. The lack of sensitivity can be an obstacle for this technology to compete with traditional analytical instrumentations. Aiming to improve the sensitivity of a paper-based colorimetric biosensor, we have applied colloids engineering in combination with filtration to lower the paper substrate backgrounds and optimize the immobilization of bio-molecules on paper. A model system consisting of an enzyme, alkaline phosphatase (ALP), and an inorganic colloid, calcium carbonate (CC), flocculated by a cationic dimethylamino-ethyl-methacrylate polyacrylamide (CPAM), demonstrated that the optimized CC flocs are best for enhancing the detecting sensitivity of ALP. The CC floc structure on paper was optimized by modulating its structure in suspension. Subsequently, the filtration process and the wicking ability of paper enabled to freeze the deposited CC structure inherited from the suspension. The incorporation of biomolecules into the CC before immobilizing on paper through filtration provided not only a better microenvironment, but also a higher surface density of immobilized biomolecules. The ALP detection limit of 117 fmol per zone (5mm circle) in the current study was fifty times lower than that of the common soaking method for biomolecule immobilization. The minimum amount of biomolecules per unit substrate area required for detection was lowered by over an order of magnitude, compared with spotting methods (i.e. inkjet printing). The improvement was also demonstrated by the steepest slope of standard curve, the lowest background, and the highest activity of the bioactive paper probed with the diluted BCIP/NBT liquid substrates., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Utilization potential of membrane filtration retentate (concentrate) of bleach plant effluent from paper industry, in bricks production, was investigated in the present study. Bricks were prepared by using retentate of membrane filtration in place of water. The physical properties measured for bricks were dimensions, density, moisture content, compressive strength, water absorption and porosity. Chemical analysis of the bricks was performed for water leachability and acid leachability, using ASTM Standard methods D 3987-06 and D 5233-92 respectively. The leachate samples were analyzed for Al, Cu, Fe, Co, Cr, Pb, Ni and Zn using AAS (atomic absorption spectrophotometer). Adsorbable organic halides (AOX) of leachate were analyzed by using AOX analyzer model ECS 1200 using column method. It was observed that the physical and chemical properties of bricks especially fire clay bricks were not adversely affected by the use of wastewater. Therefore, the organic matter of the retentate of membrane filtration creates no problems for this application., (Copyright © 2010 Elsevier B.V. All rights reserved.)