Increased anthropogenic activities have led to serious environmental problems due to pollution caused by toxic materials such as heavy metals whose levels are rising in the environment. The inefficiency and high cost of conventional methods of waste treatment have prompted the investigation of environmentally friendly and cheaper methods of treatment using natural products. In this study, G. arborea leaves powder was investigated with a view of using it as cheap material for the biosorption of Pb2+ and Cd2+ from wastewater. The effects of operational parameters like pH, biosorbent dose [g/L], initial metal ions concentration [mg/L], contact time [minutes] and stirring speed [rpm] on the biosorption efficiency [%] were determined. The optimum solution pH for Pb2+ and Cd2+adsorption was 5.0 and peak adsorption of 91.33% and 82.53% for Pb2+ and Cd2+, respectively. 5 g/L Melina leaves were enough to achieve peak removal of both metal ions. The removal of the metal ions was comparatively quick, and stability was achieved after 30 minutes. The optimum stirring speed was 250 rpm for both metal ions. The uptake efficiency of the biosorbent was determined by Langmuir and Freundlich isotherm models. The value of Langmuir isotherm separation parameter [RL] of Pb2+ ion [0.0446 - 0.78125] and Cd2+ [0.1005- 0.9482] were within range of 0 -1 indicating favorable biosorption for both metal ions. The degree of non-linearity [n] values between Pb2+ [12.79] and Cd2+ [11.79] solution concentration and biosorption in Freundlich equation were greater than 1, indicating physical biosorption of Pb2+ and Cd2+ on to G. arborea leaves. G. arborea can serve as efficient biosorbent not only for Pb2+ and Cd2+ ions but also for other heavy metal ions in a wastewater stream
Starch is a biological macromolecule with myriad of industrial uses. The growing need for starch and native starch deficiencies, have necessitated researches into under-exploited starch sources and modifications, respectively. Chrysophyllum albidum (African star apple, ASA) seed is a waste consisting of 63.94% carbohydrate in its kernel. Its starch content can be fully utilised, industrially, if it is in a suitable form and its properties understood. That necessitated the isolation of ASA kernel starch, its modification and properties assessment. Acetylation, acid-thinning and oxidation were performed on the native African star apple kernel starch, NACA, to produce the acetylated, ACCA, acid-thinned, ATCA, and oxidised, OXCA, African star apple starches, respectively. The physicochemical properties of the native and modified starches were investigated with established methods. The yield of starch was 43.76%. The acetylated and oxidised starches had low degrees of substitution. FT-IR results confirmed the introduction of carbonyl functionality into the acetylated and oxidised starches. Starch morphology revealed smooth, small rounded and truncated ellipsoid granules with diameter ranges of 7–20 µm. Swelling power of modified starches improved, except for the acid-thinned, and increased with temperature. Acetylated and oxidised starches had significantly (p < 0.05) higher water and oil absorption capacities, respectively. Acid-thinning significantly improved starch pasting properties and reduced retrogradation tendency. Modification improved the gelatinisation transition temperature of native starch. It was concluded that modification increased the industrial raw material potentials of African star apple kernel starch.
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