Radiation grafting: A voyage from bio-waste corn husk to an efficient thermostable adsorbent

Carbon quantum dots-containing poly(β-cyclodextrin) for simultaneous removal and detection of metal ions from water

This study investigates the synthesis and characterization of supramolecular composites composed of poly(β-cyclodextrin-co-citric acid) and carbon quantum dots (QDs). These composites serve a dual purpose as adsorbents and photoluminescent probes for divalent metal ions, including Ni(II), Cu(II), Cd(II), and Pb(II), which can have detrimental effects on the environment. Various characterization techniques were employed to confirm the successful synthesis of the composites and the interaction between cyclodextrins and QDs. By using mathematical tools, optimal conditions for metal adsorption were determined, resulting in the composites exhibiting high adsorption capacities, reaching 220 mg/g, and impressive removal efficiencies exceeding 90 % for Ni(II) and Cu(II). The supramolecular composites also exhibit selective adsorption of metal ions with small ionic radio and can be reused with minimal loss of efficiency. In addition to their adsorption capabilities, these composites display luminescence quenching upon the adsorption of metal ions, which can be utilized for sensing applications. Spectroscopic evaluation reveals Stern-Volmer quenching constants for the accessible fraction of QDs in the range of 3777 to 13,359 M-1. The high stability of QDs on the composites allows for long-term storage. In summary, this original supramolecular composite shows promise for simultaneously monitoring and treating water and wastewater, making it a valuable tool in environmental applications.

Tailoring Acid Free-Paper based Analytical Devices (Af-PADs) via radiation assisted modification of cellulose paper

A novel green fabrication approach is being proposed based on radiation assisted modification of Whatman filter paper 1 (WFP) for development of Acid Free-Paper based Analytical Devices (Af-PADs). Af-PADs exude immense potential as handy tools for on-site detection of toxic pollutants such as, Cr(VI), boron, etc., which have established detection protocols involving acid mediated colorimetric reactions that necessitate external acid addition. The proposed Af-PAD fabrication protocol asserts its novelty through elimination of external acid addition step, making the detection process safer and simpler. To achieve this, poly(acrylic acid) (PAA) was grafted onto WFP via a single step, room temperature process of gamma radiation induced simultaneous irradiation grafting, introducing acidic -COOH groups in the paper thereon. Grafting parameters namely, absorbed dose and concentrations of monomer, homopolymer inhibitor and acid were optimized. The -COOH groups incorporated in PAA-grafted-WFP (PAA-g-WFP) provide localized acidic conditions for colorimetric reactions between pollutants and their sensing agents, anchored on the PAA-g-WFP. Af-PADs loaded with 1,5-diphenylcarbazide (DPC) have been ably demonstrated for visual detection and quantitative estimation of Cr(VI) in water samples using RGB image analysis, with LOD value of 1.2 mg.L^-1 and a measurement range comparable to that of commercially available PADs based Cr(VI) visual detection kits.

Efficient Adsorption Performance of Lithium Ion onto Cellulose Microspheres with Sulfonic Acid Groups

The separation of Li+ from an aqueous solution has received much attention in recent years because of its wide application in batteries and nuclear energy. A cellulose microsphere adsorbent with sulfonic acid groups (named as CGS) was successfully prepared by the pre-irradiation-induced emulsion graft polymerization of glycidyl methacrylate onto cellulose microspheres through subsequent sulfonation and protonation. The adsorption performance of Li+ onto the CGS adsorbent is investigated in detail. The as-prepared CGS adsorbent exhibited fast adsorption kinetics and a high adsorption capacity of Li+ (16.0 mg/g) in a wide pH range from 4 to 10. The existence of K+ and Na+ was found to have the ability to affect the adsorption capacity of Li+ due to the cation-exchange adsorption mechanism, which was further confirmed by X-ray photoelectron spectroscopy (XPS). The column adsorption experiment indicated that the adsorption capacity of CGS agreed well with the batch adsorption, and a fast desorption could be obtained in 10 min. It is expected that CGS has potential usage in the adsorption separation of Li+ from an aqueous solution.

Kinetic Study of Corn and Sugarcane Waste Oxidative Pyrolysis

The behavior of the kinetics and pyrolysis of the corn and sugarcane waste (cob corn, husk corn, and bagasse) produced in Colombia have been evaluated in a thermobalance as a step toward their valorization, in order to recover this type of waste. For this, a kinetic model has been developed consisting of a multicomponent mechanism that seeks to describe the formation of volatile materials. This model evaluates the decomposition of hemicellulose, cellulose, and lignin from three parallel and independent reactions network. It also involves the production of other products such as fixed coal and ashes. The evaluation of the model from the kinetic parameters and the thermogravimetric curves were compared with other types of waste, in the same way the chemical characteristics of the studied waste were determined. Although the wastes of this study are completely different, it was found that the degradation behavior of the residues of this study are very similar to other lignocellulosic materials, which demonstrates again that the pyrolysis valorization is possible.

Effect of maleic anhydride content on physico-mechanical properties of γ-irradiated waste polypropylene/corn husk fibers bio-composites

Biocomposites of waste polypropylene (wPP) with 20 phr (part per 100 parts of [wPP]) corn husk fibers (CHF) as bio-filler were prepared for environmental aspect. Maleic anhydride (MAH) was used, with 5, 10 phr concentration as compatabilizer was carried out. The obtained biocomposites were irradiated by γ radiation ranging from 5 to 25 kGy. Mechanical, physical and thermal properties of the biocomposites were studied to evaluate the effect of CHF addition on the properties of obtained composites. It has been found that there is deterioration in all properties. However, by the addition of MAH, the former properties were improved. The obtained results were confirmed by Fourier transform infrared (FTIR) and scanning electron microscopy (SEM).