Functionalizing natural polymers to develop green adsorbents for wastewater treatment applications

Facile synthesis of eco-friendly alginate-chitosan bio-adsorbent for critical raw materials adsorption: A comprehensive study

Sustainable management of critical raw materials is of paramount importance to ensure a steady supply and reduce environmental impact. The application of newly synthesized and environmentally friendly ALG@CS material as a bio-adsorbent for the effective rare earth elements removal from aqueous solution has been presented. The synthesized material underwent FTIR, XPS, EDX, and SEM analysis to determine its suitability for metal uptake. To evaluate the adsorption capacity of ALG@CS for rare earth elements several factors were taken into consideration. These factors included alginate:chitosan ratios, bead size, pH level, composite mass, interaction time, metal ion concentration, and temperature, being all varied during the batch mode evaluation process. Under the optimal conditions, the maximum adsorption capacities were found to be 145.90 mg La(III)/g, 168.44 mg Ce(III)/g, 132.51 mg Pr(III)/g, 128.40 mg Nd(III)/g, 154.36 mg Sm(III)/g, and 165.10 mg Ho(III)/g. The equilibrium data fits well with non-linear three-parameter Sips and Redlich-Peterson isotherm models. The PSO model finds the highest process suitability. The synthesized ALG@CS bio-adsorbent showed excellent regenerative capacity in ten cycles, making it a suitable adsorbent for rare earth elements uptake. The unique bio-adsorbents combination allows for efficient critical raw materials adsorption providing a promising solution for their recovery and recycling.

Effect of Glycerol and Sisal Nanofiber Content on the Tensile Properties of Corn Starch/Sisal Nanofiber Films

Currently, petroleum-derived plastics are widely used despite the disadvantage of their long degradation time. Natural polymers, however, can be used as alternatives to overcome this obstacle, particularly cornstarch. The tensile properties of cornstarch films can be improved by adding plant-derived nanofibers. Sisal (Agave sisalana), a very common low-cost species in Brazil, can be used to obtain plant nanofibers. The goal of this study was to obtain sisal nanofibers using low concentrations of sulfuric acid to produce thermoplastic starch nanocomposite films. The films were produced by a casting technique using commercial corn starch, glycerol, and sisal nanofibers, accomplished by acid hydrolysis. The effects of glycerol and sisal nanofiber content on the tensile mechanical properties of the nanocomposites were investigated. Transmission electron microscopy findings demonstrated that the lowest concentration of sulfuric acid produced fibers with nanometric dimensions related to the concentrations used. X-ray diffraction revealed that the untreated fibers and fibers subjected to acid hydrolysis exhibited a crystallinity index of 61.06 and 84.44%, respectively. When the glycerol and nanofiber contents were 28 and 1%, respectively, the tensile stress and elongation were 8.02 MPa and 3.4%. In general, nanocomposites reinforced with sisal nanofibers showed lower tensile stress and higher elongation than matrices without nanofibers did. These results were attributed to the inefficient dispersion of the nanofibers in the polymer matrix. Our findings demonstrate the potential of corn starch nanocomposite films in the packaging industry.

Transparent Cellulose/Multi-Walled Carbon Nanotube Hybrids with Improved Ultraviolet-Shielding Properties Prepared from Cotton Textile Waste

Plastics offer many advantages and are widely used in various fields. Nevertheless, most plastics derived from petroleum are slow to degrade due to their stable polymer structure, posing serious threats to organisms and ecosystems. Thus, developing environmentally friendly and biodegradable plastics is imperative. In this study, biodegradable cellulose/multi-walled carbon nanotube (MCNT) hybrid gels and films with improved ultraviolet-shielding properties were successfully prepared using cotton textile waste as a resource. It was proven that MCNTs can be dispersed evenly in cellulose without any chemical or physical pretreatment. It was found that the contents of MCNTs had obvious effects on the structures and properties of hybrid films. Particularly, the averaged transmittance of cellulose/MCNT composite films in the range of 320-400 nm (T320-400) and 290-320 nm (T290-320) can be as low as 19.91% and 16.09%, when the content of MCNTs was 4.0%, much lower than those of pure cellulose films (T320-400: 84.12% and T290-320: 80.03%). Meanwhile, the water contact angles of the cellulose/MCNT films were increased by increasing the content of MCNTs. Most importantly, the mechanical performance of cellulose/MCNT films could be controlled by the additives of glycerol and MCNTs. The tensile strength of the cellulose/MCNT films was able to reach as high as 20.58 MPa, while the elongation at break was about 31.35%. To summarize, transparent cellulose/MCNT composites with enhanced ultraviolet-shielding properties can be manufactured successfully from low-cost cotton textile waste, which is beneficial not only in terms of environmental protection, but also the utilization of natural resources.

Curdlan/sodium carboxymethylcellulose composite adsorbents: A biodegradable solution for organic dye removal from water

Composite adsorbent comprised of curdlan (CURD) and sodium carboxymethylcellulose (CMC) were fabricated through a single-step heating process, targeting the removal of methylene blue (MB) from wastewater. The CURD/CMC composite adsorbents had a honeycomb porous structure. The integration of CMC not only increased the storage modulus of the CURD/CMC composite hydrogels but also affected the thermal stability and swelling behavior of the composite adsorbents in different pH solutions. Specifically, the addition of 1.2 % CMC increased the peak temperature (184.73 °C) of CURD/CMC composite adsorbent melting by 5.99 °C compared to CURD adsorbent. The addition of CMC improved the swelling ratio of the composite adsorbent at pH 3,7, and 12 with swelling ratio up to 918.07 %. The synergistic interaction between CURD and CMC led to an enhanced adsorption capacity of the aerogel for MB, achieving a maximum adsorption capability of 385.85 mg/g. Adsorption isotherm assessments further demonstrated that the Langmuir isotherm model well fitted the adsorption data of the composite adsorbent on MB. Collectively, these findings underscore the potential of the developed biodegradable adsorbents as promising adsorbents for efficiently eliminating organic dyes from water.

Sodium carboxymethyl cellulose and MXene reinforced multifunctional conductive hydrogels for multimodal sensors and flexible supercapacitors

With the growing demand for eco-friendly materials in wearable smart electronic devices, renewable, biocompatible, and low-cost hydrogels based on natural polymers have attracted much attention. Cellulose, as one of the renewable and degradable natural polymers, shows great potential in wearable smart electronic devices. Multifunctional conductive cellulose-based hydrogels are designed for flexible electronic devices by adding sodium carboxymethyl cellulose and MXene into polyacrylic acid networks. The multifunctional hydrogels possess excellent mechanical property (stress: 310 kPa; strain: 1127 %), toughness (206.67 KJ m-3), conductivity (1.09 ± 0.12 S m-1) and adhesion (82.19 ± 3.65 kPa). The multifunctional conductive hydrogels serve as strain sensors (Gauge Factor (GF) = 5.79, 0-700 % strain; GF = 14.0, 700-900 % strain; GF = 40.36, 900-1000 % strain; response time: 300 ms; recovery time: 200 ms) and temperature sensors (Temperature coefficient of resistance (TCR) = 2.5755 °C-1 at 35 °C- 60 °C). The sensor detects human activities with clear and steady signals. A distributed array of flexible sensors is created to measure the magnitude and distribution of pressure and a hydrogel-based flexible touch keyboard is also fabricated to recognize writing trajectories, pressures and speeds. Furthermore, a flexible hydrogel-based supercapacitor powers the LED and exhibits good cyclic stability over 15,000 charge-discharge cycles.