The sufficient removal of heavy metals from sewage sludge remains to be achieved. Heavy metals that exist on the cell surfaces of the microorganisms in the sludge seem to be dissolved by acid treatments. This study shows that heavy metals in sewage sludge can be removed easily by treating a sludge filter cake with phosphoric acid containing hydrogen peroxide for 1 h at room temperature. Phosphoric acid of 8% concentration with hydrogen peroxide showed good removal rates of heavy metals comparable to those by 1 N hydrochloric acid. Copper is easily removed from the sludge in the presence of hydrogen peroxide. From the results of the investigation of the solubilities of several copper compounds into phosphoric acid with or without hydrogen peroxide, the copper in the sludge does not exist as copper sulfides, but it seems to exist as copper thiolates containing Cu(I) in biopolymers. In this process, the phosphoric acid used for the removal of heavy metals is almost entirely recovered and is reused. Sewage sludge with low content of heavy metals can be recycled as a useful resource.
A series of new sympathomimetic amines containing an 8-hydroxycarbostyril moiety was synthesized. These compounds probably exist as resonance hybrids having two acidic hydrogen atoms in locations approximating to those of the hydroxyl groups of catechol-containing adrenergic agents. In an in vitro test, many of these compounds showed potent activity for relaxation of guinea pig tracheal smooth muscle. One of the compounds was 24 000 times more potent than isoproterenol. Their actions on cardiac muscle were also examined in vitro by measuring increase in the beating rate of the right atria of guinea pigs. Several of the compounds appeared to be beta-selective. Some of the compounds seem suitable for use as bronchodilators. The structure-activity relationships of these compounds were discussed in comparison with those of catecholamines.
The isomers of erythro-5-(1-hydroxy-2-isopropylaminobutyl)-8-hydroxycarbostyril (1), a new potent and beta2-selective bronchodilator, were synthesized by optical resolution of compound 1 and inversion of the erythro to the threo isomers. The isomers were tested for activities to inhibit histamine-induced bronchospasm and to increase the heart rate of anesthetized dogs. Racemic and (-)-erythro-1 showed potent and beta2-selective bronchodilater activities. Among the isomers, (-)-erythro-1 showed the highest activities and (+)-erythro-1 showed the lowest.
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