Mamiko Araki

Removal of phosphate by aluminum oxide hydroxide

The development and manufacture of an adsorbent to remove phosphate ion for the prevention of eutrophication in lakes are very important. The characteristics of phosphate adsorption onto aluminum oxide hydroxide were investigated to estimate the adsorption isotherms, the rate of adsorption, and the selectivity of adsorption. Phosphate was easily adsorbed onto aluminum oxide hydroxide, because of the hydroxyl groups. The adsorption of phosphate onto aluminum oxide hydroxide was influenced by pH in solution: the amount adsorbed was greatest at pH 4, ranging with pH from 2 to 9. The optimum pH for phosphate removal by aluminum oxide hydroxide is 4. The selectivity of phosphate adsorption onto aluminum oxide hydroxide was evaluated based on the amount of phosphate ion adsorbed onto aluminum oxide hydroxide from several anion complex solutions. It is phosphate that aluminum oxide hydroxide can selectively adsorb. The selectivity of phosphate onto aluminum oxide hydroxide was about 7000 times that of chloride. This result indicated that the hydroxyl groups on aluminum oxide hydroxide have selective adsorptivity for phosphate and could be used for the removal of phosphate from seawater.

TRIHALOMETHANE REMOVAL BY ACTIVATED CARBON FIBER

For the safety of drinking water, trihalomethanes are removed by adsorption onto activated carbon fiber from single-component solutions. The amounts adsorbed onto adsorbents with large surface area and/or pore volume were small. Stronger surface hydrophobicity of adsorbent was correlated with a larger amount of trihalomethanes adsorbed. A trihalomethane with bromine was adsorbed to a greater extent than that with chlorine. The differences in the amounts adsorbed among trihalomethanes can be explained by the polarity of trihalomethane molecules. The amount of trihalomethanes adsorbed was mainly dominated by the strength of hydrophobicity of activated carbon fibers.

Removal of bisphenol a in soil by cyclodextrin derivatives

Abstract The apparent aqueous solubility of the endocrine disruptor in hydroxypropyl‐cyclodextrin (HP‐CD) solutions was investigated for evaluating the remediation of soil contamination and ground water pollution. The apparent solubility of bisphenol A (BPA) in water was significantly increased in HP‐CD solutions. The solubilization effect of HP‐CDs is caused by the formation of inclusion complexes of BPA and cyclodextrin. The relative aqueous‐phase concentration of BPA linearly increased with increasing HP‐CD concentration. The solubility of BPA increased in the order of the addition of HP‐a‐CD, HP‐7‐CD, and HP‐ß‐CD. However, it did not depend upon the degree of hydroxypropylation substitution. It is concluded that HP‐CD may be utilized for the remediation of soil contamination.

Relationship between surface‐modified activated carbons and volatile chlorinated hydrocarbons

The interactions between surface‐modified activated carbons and trichloroethylene (TCE) or tetrachloroethylene (PCE) were estimated based on the adsorption isotherms and constants of the Freundlich and Langmuir equations. This result indicated that PCE strongly interacts with the activated carbon surface compared to TCE, because PCE is a more hydrophobic compound than TCE. The adsorption of TCE onto the activated carbon was effected to the presence of water, while that for PCE was not. The removal of TCE has to use for more hydrophobic activated carbon, that is, the activated carbon treated with hydrogen gas (AC‐Red). On the other hand, the removal of PCE in water could be removed by the untreated activated carbon (AC).

Formation of trihalomethanes from dyes by ozone treatment

Abstract The amount of chloroform produced from dyes (orange II, methylene blue, and methylrosanilinium chloride) and humic acid by adding chlorine after the ozone treatments was investigated. Some dyes and humic acid were degraded by ozone and produced polar and acidic organic compounds. The amount of chloroform produced from orange II increased or decreased with the ozonization time, while that produced from methylene blue and humic acid decreased with ozonization time. Methylrosanilinium chloride did not produce the trihalomethane by chlorine disinfection. Thus, some but not all dyes produce trihalomethanes by ozone treatment and chlorine disinfection.