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Oxidized starch, an additive used in paper manufacturing and products for construction industry, is usually produced using harmful oxidant, such as hypochlorites or periodates. In this study, a simple and efficient eco-friendly laboratory and industrial procedures for starch oxidation were developed. The procedure involves application of small amounts of more environmentally friendly oxidant, hydrogen peroxide, a novel special metal complex catalyst such as copper(II) citrate and copper(II) ricinoleate and biobased plasticizers. Optimization procedure, with respect to the quantity of hydrogen peroxide and temperature in the presence of iron(II) sulphate catalyst, was performed by using the response surface methodology. Comparative analysis of the use of the other catalysts that is copper(II) sulphate, copper(II) citrate and copper(II) ricinoleate, indicated copper(II) citrate as the catalyst of choice. Improvement of starch is achieved using three plasticizers: ricinoleic acid (RA), diisopropyl tartarate, as well as epoxidized soybean, linseed and sunflower oils. The effects of hydrogen peroxide and catalyst concentrations, as well as the reaction temperature in the presence of naturally based plasticizers on the physicochemical, thermal and morphological properties of oxidized starch are presented. According to the results obtained in initial experiments, the optimal industrial process is based on the use of copper(II) citrate (0.1 %) as a catalyst and RA (3 %) as a plasticizer.

As a renewable resource, starch is considered to be fully biodegradable and nonpolluting to the environment but the hygroscopicity of starch is the main disadvantage for wider applicability in the production of a polymer-based material. Hydrophobically modified starch prepared using natural-based plasticizers/modifiers in a first step ([−]-diisopropyl D-tartrate [DiPT], ricinoleic acid [RA] and epoxidized soybean oil [ESO]), and maleated polypropylene (MAPP) in a second step contributed to better compatibility, and thus reinforcing of composites. Tailored processing conditions, structural/morphological properties, hydrophobicity, and water-resistance of the modified starch were established. In addition, the Charpy impact and tensile strength of composites, based on poly(ethylene-co-acrylic acid) (EAA) and modified starches, were determined. Increased tensile strength and Young modulus of the composite using starch-modified with DiPT-MAPP, that is, 3 and 83%, respectively, indicated the possible applicability of obtained materials.

This study aims to investigate the effect of alkalization and chemical coupling methods on the surface and adsorption properties of waste cotton and cotton/polyester yarns. The simple and cheap alkali treatment was performed using 10% and 18% NaOH solution, while the chemical coupling method involved combining cotton and cotton/polyester yarns and fly ash, using sodium carboxymethyl cellulose and sodium alginate as binders. Morphological and surface characteristics of unmodified and modified cotton and cotton/polyester yarns were analyzed by scanning electron microscopy and Fourier transform infrared spectroscopy, while adsorption properties were assessed by the removal of lead and cadmium ions from aqueous solution. It was found that chemical modification with 18% NaOH solution positively affected the adsorption properties of only cotton yarns, increasing the removal efficiency of lead ions up to 75%. On the other hand, modification with fly ash improves the adsorption properties of both, cotton and cotton/polyester yarns, increasing the efficiency in removing lead ions by using sodium carboxymethyl cellulose, and cadmium ions by using alginate as a binder. Using the chemical coupling method, effective adsorbents are obtained starting from waste yarn, which gives it added value, the amount of non-degradable waste material can be reduced and the criteria of a cleaner environment and circular economy can be met.

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