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In this study, radiation-grafted adsorbents were developed and evaluated for their capacity to remove trivalent chromium (Cr3+) from aqueous solutions. The adsorbents were prepared through electron beam induced grafting of glycidyl methacrylate (GMA) onto polypropylene nonwoven fabric (PP), followed by post-grafting functionalization of the PP-g-PGMA with ethylenediamine (EDA), iminodiacetic acid (IDA), phenylphosphonic acid (PPO), and phenylphosphinic acid (PPI). The Fourier-transform (FTIR) spectroscopy and thermogravimetric analysis (TGA) results suggest that the PP substrate was successfully grafted and functionalized. Among the adsorbents evaluated, the EDA functionalized PP-g-PGMA showed the best performance, removing 90-99.5% of Cr3+ from 50 mL of 10 ppm Cr3+ solution at pH 3.5 using an adsorbent with 0.159 mmol EDA groups after adsorption for 24 h with continuous stirring at room temperature. The bound Cr3+ was stripped off from the spent adsorbent by 0.5 M HCl at 70% efficiency, which was also performed for 24 h of continuous stirring at room temperature. The adsorption of Cr3+ by the EDA-functionalized fabric fit best with the Langmuir adsorption isotherm (R² = 0.967), possibly indicating a monolayer coverage of the adsorption sites. Moreover, the EDA-functionalized fabric was found to be highly selective toward Cr3+, even in the presence of high concentrations of cations commonly present in tanning wastewater such as Na, Mg, and Fe. The results suggest the potential of the EDA functionalized PP-g-PGMA adsorbent to be used in the treatment of tanning industry wastewater containing ppm levels of Cr3+. [ABSTRACT FROM AUTHOR]

Scandium is a rare earth element that has a wide range of uses in modern technology. The conventional recovery of scandium is commonly done by solvent extraction using organophosphorus compounds. This process however produces a lot of waste extractants. To circumvent this challenge, a model organophosphorus compound phenylphosphinic acid (PPI) was immobilized to a polymer support fabric to produce a Sc(III) adsorbent for high throughput scandium recovery with less waste generation. Polymer support (PP‐g‐PGMA) for the organophosphorus compound was synthesized using radiation‐induced graft polymerization. Successful post‐polymer modification of the PGMA grafts to attach PPI groups was carried out using 1 M PPI in isopropanol at 80°C for 4 h, achieving a maximum functional group density of 1.32 mmol/g. The obtained PP‐g‐PGMA‐PPI fabrics were used in the batch Sc(III) adsorption experiments. The results showed that PP‐g‐PGMA‐PPI effectively adsorbed low concentrations of Sc(III) at a pH of at least 2.0. More than 98% adsorption was achieved using 1 ppm Sc(III). The synthesized adsorbent was also shown to be selective for Sc(III) even in the presence of Fe(III) and Al(III) ions. PP‐g‐PGMA‐PPI adsorbent fabrics are therefore promising alternatives to solvent extraction methods and ion‐exchange granular resin technologies in the recovery of scandium. [ABSTRACT FROM AUTHOR]

Super water absorbent (SWA) for agricultural applications must be optimized to withstand diminishing consequences in real soil system. A 33 × 12 full factorial design and soil water retention experiments were explored to optimize agricultural SWA made from acrylic acid (AA) and cassava starch. Four synthesis parameters such as degree of neutralization (DN), AA concentration, cassava starch concentration, and absorbed dose affecting the gel properties of SWA were investigated in the experimental design. The results showed that AA concentration and DN has strong interaction effects toward the degree of swelling (DS), gel fraction (GF), and gel strength (GS) of SWA. The soil water retention of SWA reduces with time due to microbial degradation and multivalent cations present in the soil. The optimum formulation is 20% AA 10% Starch 30% DN 10 kGy has predicted values (176 ± 68 g/g DS, 93 ± 5% GF, and 137 ± 23 kPa GS) close to the experimental values (132 ± 0.2 g/g DS, 91 ± 0.2% GF, and 141 ± 88 kPa GS). The chosen optimized formulation is 20% AA 7.5% starch 30% DN 20 kGy with 46% biodegradability after 218 days and stable soil water retention compared to commercial SWAs. [ABSTRACT FROM AUTHOR]

Carboxymethyl κ-carrageenan (CMKC), with different degrees of substitution (DSs), were gamma-irradiated in viscous or paste solutions. Successfully synthezised chemically crosslinked hydrogels showed dependence on the DS, concentration, and radiation dose. The highest gel fraction was 76% exhibited by CMkC-3s hydrogel with a DS of 1.58. The hydrogels showed different swelling degrees in water and saline. Swelling behavior vs. time, in both solvents, corresponded to 2nd-order kinetics. The CMkC-3s at 20% concentration irradiated at 15 kGy had the highest water absorption of 334 g water/g dry gel. Selected hydrogels were evaluated for applications as wound dressing, as water retainer in sandy soil, and as metal adsorbent. As a wound dressing, CMkC-2s and CMkC-3s hydrogels exhibited considerable tensile strengths, abilities to absorb pseudo extracellular fluid, and extractables with pH/conductivity conducive for healing promotion. Also, the CMkC-3s hydrogel had no cytotoxic potential based on the MTT test. As water retainer in sandy soil, test samples with 0.1, 0.3, and 0.5% CMkC-3s granules initially retained 25.1%, 32.2%, and 42.6% water, respectively, compared to 19.2% of the sandy soil alone. On Day 7, the three sandy soil-CMkC groups still had 13.7-29.3% water, while the control had only 3.85%. In the batch adsorption studies, the hydrogels adsorbed Cu2+, Zn2+, Cd2+, and Pb2+ heavy metals in the solution at different capacities, with Cd2+ as the highly adsorbed and Pb2+ as the least. The CMkC-3s hydrogel showed the highest metal uptake and adsorption efficiency, followed by CMkC-2s, then CMkC-1s. The CMkC-3s hydrogel, further tested on pH effect, exhibited optimum metal uptake at neutral pH. [ABSTRACT FROM AUTHOR]