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Acrylic acid is a hydrophilic monomer which becomes the most popular material used to synthesize superabsorbent polymer. In this recent study, acrylic acid was partially neutralized with KOH and mixed with chitosan to form a superabsorbent hydrogel poly (acrylic acid)-graft-chitosan by using of gamma ray irradiation technique. The aim of this study was to determine the optimum composition of KOH in acrylic acid partial neutralization process for enhancing the production of grafted polymer. The degree of neutralization was varied (0, 25, 50, 75, and 100)% and the effect on the superabsorbent characteristics were studied. Hydrogel products were characterized by Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM). The gel content, swelling ratio, Equilibrium Degree of Swelling (EDS), and Thermal Analysis were also performed. The highest water swelling capacity was 715 (g water/g dry hydrogel), and the gel content was 91.23%, resulted from 75% of acrylic acid neutralization. The swelling capacity of the products was also tested in urea and NaCl solutions and reached 750 (g urea solution/g dry hydrogel) for urea and 378,33 (g NaCl solution/g dry hydrogel) for NaCl. The huge water absorption capacity indicated that the hydrogel from this research was a superabsorbent product which was suitable for hygiene products application. The degree of neutralization did not show a significant influence on the thermal resistance of the grafted hydrogel produced in this study.

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Calcite-induced precipitation methods (CIPMs) have recently become potential techniques in geotechnical engineering for improving the shear strength of sandy soil. One of the most promising methods among them is enzyme-induced calcite precipitation (EICP). In this technique, a mixed solution composed of reagents and the urease enzyme, which produces calcite, is utilized as the grouting material. The precipitated calcite in granular soil provides ties among the grains of soil and limits their mobility, thus promoting an improvement in strength and stiffness and also a reduction in the hydraulic conductivity of sandy soil. This paper discusses the potential increase in the strength and stiffness of the soil, the additional materials for grouting, the effect of these materials on the treatment process, and the engineering properties of the soil. The possible sources of the urease enzyme and the applicability of the EICP method to other soil types are also discussed in this paper. The environmental and economic impacts of the application of EICP are also presented. The envisioned plans for application, potential advantages, and limitations of EICP for soil stabilization are discussed. Finally, the primary challenges and opportunities for development in future research are briefly addressed.

Organic soil has a high content of water and compressibility. Besides that, it has a low specific gravity, density, and shear strength. This study evaluates the applicability of the soybean crude urease for calcite precipitation (SCU-CP) method and its effectiveness in organic soil as a soil-amelioration technique. Various soybean concentrations were mixed with a reagent composed of urea and calcium chloride to produce the treatment solution. Its effect on the hydrolysis rate, pH, and amount of precipitated calcite was evaluated through test-tube experiments. SEM-EDS tests were performed to observe the mineralogy and morphology of the untreated and treated samples. The treatment solution composed of the reagent and various concentrations of soybeans was applied to organic soil. The increasing strength of the organic soil was evaluated using direct shear (DS) and unconfined compression (UCS) tests. The test-tube results show that a hydrolysis rate of 1600 u/g was obtained when using 50 g/L of soybeans with a precipitation ratio of 100%. The mechanical tests show a significant enhancement in the parameters of the organic soil’s shear strength. A shear strength improvement of 50% was achieved in this study. A UCS of 148 kPa and cohesion of 50 kPa was obtained in the treated samples of organic soil. This research elucidates that the SCU-CP is an effective technique for improving organic soil’s shear strength.