Valorization of wheat straw in food packaging: A source of cellulose

Fabrication of cellulose-collagen based biosorbent as eco-friendly scavengers for uranyl ions

The aim of the present research is to fabricate a biosorbent using agricultural waste for removal of uranium from contaminated water i.e. "waste to wealth" approach. Cellulose extracted from wheat straw was mercerized and a novel semi-interpenetrating polymer network (semi-IPN) was fabricated through graft copolymerization of polyvinyl alcohol onto hybrid mercerized cellulose + collagen backbone. Response surface methodology was used for optimization of different reaction parameters as a function of % grafting (195.1 %) was carried out. Semi-IPN was found to possess higher thermal stability. Adsorption results revealed that the optimum parameters for the elimination of uranium using semi-IPN were: adsorbent dose = 0.15 g, pH = 6.0, contact time = 120 min and initial U (VI) concentration = 100 μg/L. The pseudo-second-order kinetic model gave the best description of the adsorption equilibrium data as the calculated qe value is nearest to the experimental qe for the different initial U(VI) concentrations. Adsorption experiments followed Langmuir isotherm with R2 = 0.999. Furthermore, recyclability and reusability studies showed that the adsorption efficiency of semi-IPN was 82 % after 5 cycles indicating the superior recycling execution of fabricated biosorbent. Thus, the fabricated ecofriendly device can be used effectively for the removal of uranium from contaminated wastewater sources.

Functional cellulose-derived epoxy cross-linked with BADGE resin to construct high-performance epoxy composites

The development of equipped bio-based epoxy materials has been gaining much attention recently. Nevertheless, finding the balance between the structure and properties of materials remains a significant challenge. In this work, cellulose-based epoxy (PHPCEP) with "soft" and "hard" cooperative structures was designed and demonstrated to endow bisphenol A diglycidyl ether (BADGE) with excellent toughness, heat resistance, mechanical strength, glass transition temperature, thermal stability, and solvent resistance. When 5 wt% PHPCEP was incorporated into BADGE composites, the resulting materials exhibited the maximum flexural strength (121.9 MPa) and tensile strength (71.4 MPa), a high glass transition temperature (148.3 °C), and 10 wt% PHPCEP/BADGE demonstrated the highest impact strength (70.5 kJ/m2). These figures are 18.8 %, 16.1 %, 21.5 %, and 254.3 % higher than the corresponding values of neat BADGE. The results of dynamic mechanical properties and heat degradation of the cured specimens also suggest that PHPCEP/BADGE materials have superior stiffness and toughness than neat BADGE, which could be attributed to the strong interaction between PHPCEP and BADGE, delivering better thermal stability for the composites compared to the pristine resin. Considering the remarkable effect, this work provides an effective way of highly efficient utilization of abundant cellulose and a high-performance additive for composite materials.

Carboxyl-modified nanocellulose (cNC) enhances the stability of cNC/pullulan bio-nanocomposite hard capsule against moisture variation

The quality of polysaccharide-based films and hard capsules is often affected by changes in relative humidity, manifesting as unstable water content, and changes in mechanical strength that make them brittle or soft. Herein, carboxyl-modified nanocellulose (cNC) was prepared and used as a new component to successfully improve the moisture resistance of cNC/pullulan/high-acyl gellan bio-nanocomposite hard capsules (NCPGs). Homogenously dispersed cNC in the pullulan/high-acyl gellan matrix could render the formation of more hydrogen bonds that provided additional water-binding sites and limited the free movement of pullulan and high-acyl gellan molecular chains within NCPGs. This contributed to a decreased amount of pooling adsorption water and an increased amount of Langmuir adsorption water in NCPGs, as compared to pullulan/high-acyl gellan hard capsules (PGs) without cNC. Therefore, the equilibrium moisture content (EMC) values of NCPGs decreased at 83 % relative humidity and increased at 23 % relative humidity compared to those of PGs. Together with enhanced mechanical and barrier properties, NCPGs effectively protected encapsulated amoxicillin and probiotic powder from changes in the outside humidity. Additionally, NCPGs exhibited faster drug release. This study presents a new mechanism and strategy for fabricating films and hard capsules with enhanced stability against moisture variation.

Biodegradable, UV-blocking, and antioxidant films from lignocellulosic fibers of spent coffee grounds

Plastics are strong, flexible, and inexpensive and hence desirable for packaging. However, as they biodegrade very slowly, their waste remains a global burden and pollution, warranting a search for safer alternatives. Towards this end, residual fibers from biowaste, such as spent coffee grounds (SCGs), stand out for creating biodegradable packaging materials. Herein, lignocellulosic fibers from SCG were extracted, and various amounts (0.6, 0.8, 1.0, and 1.2 g) were solubilized using 68 % ZnCl2 and crosslinked with salt (CaCl2) amounts 0.1, 0.2, 0.3 and 0.4 g and prepared biodegradable films. The films were characterized for their color, thickness, moisture content, tensile strength, elongation at break, water vapor permeability, transmittance of electromagnetic radiation, biodegradability, and antioxidant properties. The results reveal that the films possess the highest tensile strength of 26.8 MPa. The tensile strengths are positively correlated to salt and SCG extract amounts. The percentage of elongation decreased with an increase in the calcium ions but increased with SCG residue increment. The films biodegraded in the soil, and most lost >80 % of their initial weight in 45 and 100 days, respectively, at 30 % and 12 % soil moisture. Biodegradability and water vapor permeability decreased with an increase in salt content. Films also showed antioxidant properties and blocked UV and IR radiation significantly. Overall, this research involving green and recyclable chemicals in preparation of SCG residue fibers is a promising, economical, and sustainable route to produce strong biodegradable films to replace petrochemical plastics and thus is an attractive contribution to the circular bioeconomy.

Value addition of rice straw cellulose fibers as a reinforcer in packaging applications

The potential use of agro-waste in food packaging applications is receiving remarkable attention due to its sustainable approach and biodegradable properties. As typical lignocellulosic biomass, rice straw (RS) is widely produced but is usually abandoned and burned, causing tremendous environmental concerns. The exploration of using RS as the source of biodegradable packaging materials is promising for economically converting this agricultural waste into packaging material, thereby providing a considerable solution for RS disposal and an alternative solution to synthetic plastic waste. Polymers have been infused with nanoparticles, fibers, and whiskers, along with plasticizers and cross-linkers, and fillers like nanoparticles and fibers. They have also been blended with natural extracts, essential oils, and other synthetic and natural polymers to improve RS properties. There is still much research to be done before this biopolymer can be applied at an industrial level in food packaging. In this respect, RS can be valued for packaging to add value to these underutilized residues. This review article focuses on the extraction methods and functionality of cellulose fibers and their nanostructured forms from RS and their utilization in packaging applications.

Cellulose/Grape-Seed-Extract Composite Films with High Transparency and Ultraviolet Shielding Performance Fabricated from Old Cotton Textiles

Plastics displaying many merits have been indispensable in daily life and they still maintain the strong momentum of development. Nevertheless, petroleum-based plastics possess a stable polymer structure and most of them are incinerated or accumulated in the environment, leading to devastating impacts on our ecology system. Thus, exploiting renewable and biodegradable materials to substitute or replace these traditional petroleum-derived plastics is an urgent and important task. In this work, renewable and biodegradable all-biomass cellulose/grape-seed-extract (GSEs) composite films with high transparency and anti-ultraviolet performance were fabricated successfully from pretreated old cotton textiles (P-OCTs) using a relatively simple, green, yet cost-effective, approach. It is proved that the obtained cellulose/GSEs composite films exhibit good ultraviolet shielding performance without sacrificing their transparency, and their UV-A and UV-B blocking values can reach as high as nearly 100%, indicating the good UV-blocking performance of GSEs. Meanwhile, the cellulose/GSEs film show higher thermal stability and water vapor transmission rate (WVTR) than most common plastics. Moreover, the mechanical property of the cellulose/GSEs film can be adjusted by the addition of a plasticizer. Briefly, the transparent all-biomass cellulose/grape-seed-extracts composite films with high anti-ultraviolet capacity were manufactured successfully and they can be used as potential materials in the packaging field.