Acetylation of native hydrolyzed and oxidized, maize starch has been studied. The different factors affecting acetylation process were investigated. These factors include liquor ratio, acetic anhydride, perchloric acid concentration, reaction time and temperature. Also investigated were characterization and application of the acetylated starches in textile warp sizing. The acetyl content increases to reach a maximum and then decreases on increasing either liquor ratio or perchloric acid concentration. Also it increases with increasing acetic anhydride concentration within the range examined whereas the acetylation reaction efliciency 010 decreases. Hydrolysis of starch prior acetylation inhances the susceptibility of the starch towards acetylation whereas oxidation do the reverse. The solubility of acetylated starches derived from hydrolyzed or oxidized starches increases more than that of acetylated native starch. The solubility depends on the extent of acetylation and of the modification prior acetylation. Acetylation of starch improves its sizeability of cotton yarns. Darstellung und Charakterisierung von Stsrkeacetat. Die Acetylierung von nativer, hydrolysierter und oxidierter Maisstarke wurde untersucht. Die verschiedenen, den AcetylierungsprozeR beeinflussenden Faktoren wurden ermittelt. Zu diesen Faktoren gehoren das Fliissigkeitsverhaltnis, Acetanhydrid-und Perchlorsaurekonzentration, Reaktionszeit und -temperatur. Auch die Charakterisierung und Anwendung der acetylierten Starken bei der Textilfadenschlichtung wurden vorgenommen bzw. untersucht. Der Acetylgehalt nirnmt bis zu einem Maximum zu und nimrnt dann entweder rnit der Zunahme des Fliissigkeitsverhaltnisses oder der Perchlorsaurekonzentration ab. Er nimmt auch mit zunehmender Acetanhydridkonzentration in dern untersuchten Bereich zu, wahrend die prozentuale Reaktionswirksamkeit abnimmt. Die Hydrolyse der Starke vor der Acetylierung erhoht die Angreifbarkeit der Starke gegeniiber der Acetylierung, wahrend die Oxidation das Gegenteil bewirkt. Die Loslichkeit der acetylierten Starken, die aus hydrolysierten oder oxidierten Starken gewonnen waren, wird starker erhoht als die von acetylierten nativen Starken. Die Loslichkeit hangt ab vom AusmaR der Acetylierung und von der Modifizierung der Starke vor der Acetylierung. Die Acetylierung von Starke verbessert ihre SchlichtFdhigkeit bei Baumwollgarnen. 280 220 173 110 * Centipoise. Different concentrations of hydrochloric acid and potassium permanganate were used for hydrolysis and oxidation of starch, respectively. 394 starch/starke 47 (1995) Nr

Agricultural wastes have great potential for the removal of heavy metal ions from aqueous solution. The contamination of water by toxic heavy metals is a worldwide environmental problem. Unlike organic pollutants, the majority of which are susceptible to biological degradation, heavy metals do not degrade into harmless end products. Discharges containing cadmium, in particular, are strictly controlled because of the highly toxic nature of this element and its tendency to accumulate in the tissues of living organisms. This work aims to develop inexpensive, highly available, effective metal ion adsorbents from natural wastes as alternatives to existing commercial adsorbents. In particular, Tamrix articulata wastes were modified chemically by esterification with maleic acid to yield a carboxyl-rich adsorbent. The adsorption behavior of treated Tamrix articulata wastes toward cadmium ions in aqueous solutions in a batch system has been studied as a function of equilibration time, adsorbent dose, temperature and pH. Results showed that the maximum adsorption capacity was 195.5 mg/g in a pH 4 solution at 30 °C with a contact time of 120 min, an initial concentration of 400 mg/L and an adsorbent dose of 0.3 g/L. The kinetic data were analyzed using pseudo-first-order and pseudo-second-order kinetic models. It was shown that the adsorption of cadmium could be described by a pseudo-second-order equation. The experimental data were also analyzed using the Langmuir and Freundlich models of adsorption. Thermodynamic parameters such as ΔGo, ΔHo and ΔSo have been evaluated and it has been found that the sorption process was spontaneous and exothermic in nature. From all of our data, we conclude that the treated Tamrix articulata wastes investigated in this study showed good potential for cadmium removal from aqueous solutions.

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Peanut hulls were modified chemically by esterification with citric acid under conditions which yielded hulls rich in carboxyl content. The esterified products thus obtained were used in the removal of Co(II) and Ni(II) ions from aqueous solutions. The factors affecting the esterification reaction and the adsorption of the metal cations onto the peanut hulls before and after esterification were thoroughly investigated. The results obtained highlighted the following conclusions. The optimum conditions for esterification involve the treatment of peanut hulls (1 g) with 12.4 mmol citric acid in the presence of a very small amount of water for 2 h at 140°C. Similarly, the optimum pH for the adsorption of cobalt(II) ions onto the peanut hulls citrate was 7.0. The adsorption capacity, qe (mg/g), of Co(II) ions onto the peanut hulls citrate increased on increasing the extent of esterification, expressed as mequiv. —COOH/100 g sample. The maximum values for the adsorption capacity, qmax, were 28.7 mg/g and 270.3 mg/g on native and peanut hulls citrate, respectively. The qmax values for of Ni(II) ion adsorption were 5 mg/g and 175.4 mg/g on native and peanut hulls citrate, respectively. The equilibrium data were well fitted by the Langmuir and Freundlich adsorption models and showed the large capacity of peanut hulls citrate in the removal of Co(II) and Ni(II) ions from aqueous solutions.