Treatment or processing of starch with organic acids (citric, stearic, succinic, and malic acids) can be used to obtain starch properties like low retrogradation, desirable viscosity, shear resistance, and high resistant starch. Esterification, cross linking, and hydrolysis of starch may occur after modification with organic acids (citric, succinic acid, malic acid) whereas a complex between starch and stearic acid may be formed on use of stearic acid. The conditions of reactions namely duration, starch acid concentration ratio, and temperature may influence physicochemical and structural properties of starch. Citric acid, succinic acid, stearic acid, and malic acid are regarded as "GRAS" and thus the starch citrate, starch succinate, starch stearate, and starch maleate are widely used in manufacturing of starch films, blends, nanoparticles, fat replacer, viscosity enhancer, and many other products. This review paper discusses the reaction conditions of organic acid modification of starches along with their influence on physicochemical and structural characteristics.
As(III) presence in low concentration (1-5 mg/L) in water presents a challenging problem in its removal. In the present study, biochar prepared by pyrolysis of mustard cake and loaded with Fe-Mn binary oxides through hydrothermal technique was used for adsorptive removal of As(III) from water in batch and continuous mode. The synthesised biochar exhibited mesoporous structures in the range of 2-50 nm (based on BET analysis). The maximum adsorption capacity (95.7 mg/g) obtained using biochar loaded with both Fe-Mn oxides was found to be 1.4 times higher than that of pristine biochar. The adsorption equilibria was best described by Freundlich isotherm (based on R 2 and χ 2) suggesting that the As(III) adsorption was multilayered. The external mass transfer coefficients (β L = 10-5 cm 2 /s) were observed to be higher than film (D f = 10-7-10-9 cm 2 /s) and intraparticle (D i = 10-9 cm 2 /s) diffusivities in batch mode. In column studies, Thomas model gave the best correlation coefficient (R 2 > 0.95) and the adsorption was limited by external mass transfer. Kinetic rate constant decreased with increase in initial As(III) concentration and flow rate. The oxide loaded biochar exhibited reusability up to three times for As(III) removal.
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