Naohito Kawasaki

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.

Selective adsorption behavior of phosphate onto aluminum hydroxide gel.

The specific surface area and X-ray diffraction patterns for an aluminum hydroxide gel (AHG) calcined at 300-1150 degrees C, the number of surface hydroxyl groups in the AHG, and the adsorption isotherms of phosphate on AHG were measured in order to develop a phosphate recovery agent. AHG was transformed into gamma- and alpha-alumina by the calcinations treatment. The amount of phosphate adsorbed onto AHG increases at calcining temperatures of 300-700 degrees C and decreases above a calcining temperature of 800 degrees C. It was found that AHG selectively adsorbs phosphate ions, but not other anions, and shows the highest adsorption capacity at pH 4-6. Further, the alkali resistance of AHG increased with calcination, and more than 80% of the phosphate adsorbed with an NaOH aqueous solution underwent desorption. The addition of colloidal alumina and colloidal silica resulted in the formation of granules of 500-840 microm size. The amount of phosphate adsorbed onto AHG after granulation was similar to that before granulation. Thus, the phosphate absorption capacity of AHG did not decrease after granulation suggesting that AHG can be used as a phosphate adsorbent.

Decolorization of Indigo Carmine by Charcoal from Extracted Residue of Coffee Beans

Abstract The adsorption ability of charcoal from extracted residue of coffee beans for indigo carmine removal was investigated by the batch method. Differences in the removal ratio and removal rate of indigo carmine could be explained by differences in the properties of charcoal. In the relationship between the amount of indigo carmine adsorbed and the square root of elapsed time, a good linearity was recognized. Since the relationship between the amount of indigo carmine adsorbed and square root of elapsed time showed a good linearity, the intraparticle diffusion of indigo carmine onto pores of adsorbents was identified as the rate-limiting step in the adsorption process.

Bleaching rapeseed and soybean oils with synthetic adsorbents and attapulgites

Efficiencies of synthetic adsorbents and attapulgites in bleaching alkali-refined rapeseed and soybean oils ranged from 13–53% and 93–97%, respectively. The Freundlich equation was more applicable than the Langmuir equation to the experimental adsorption isotherms of β-carotene on attapulgites. Bleaching with attapulgites reduced tocopherols by 12.5–29.5% in rapeseed oil and by 18.9–44.8% in soybean oil. Cosmetic-grade attapulgite was superior to the others in bleaching efficiency, equilibrium amount adsorbed and removal of free fatty acids.

Adsorption isotherms of pigments from alkali-refined vegetable oils with clay minerals

Adsorption isotherms of pigments from alkali-refined oils (rapeseed, soybean, wheatgerm, safflower, corn, cottonseed and sunflower) were measured to investigate the applicability of the Langmuir and Freundlich equations and to elucidate the adsorption characteristics of pigments on sepiolites and standard activated clay. The Freundlich equation was more applicable to the experimental adsorption isotherms. The equilibrium amount adsorbed, acidity, pore size distribution and inflection of the Freundlich isotherms could be explained by assuming that pigments were adsorbed on the stronger acid sites in smaller pores at low concentration, and then in the larger ones when the concentration increased. The amount adsorbed increased with a rise in adsorption temperatures from 70 to 110°C, and the heat of adsorption was below 10 kcal/mol. The results indicate that pigments were physically adsorbed on the acid sites activated at higher adsorption temperatures.

ADSORPTION REMOVAL OF PARAQUAT AND DIQUAT ONTO ACTIVATED CARBON AT DIFFERENT ADSORPTION TEMPERATURE

The efficacy of activated carbon as an oral adsorbent in removing paraquat and diquat from purified water and physiological saline solution at different temperatures was investigated for the primary treatment of acute poisoning. The amounts of paraquat and diquat adsorbed onto activated carbon were large in low temperature condition. The adsorption mode of paraquat and diquat onto activated carbon was mainly physical adsorption. It was recognized that the high adsorption ratio of paraquat and diquat onto activated carbon was obtained by the administration of low temperature suspended solution which was a mixture of activated carbon and gastrointestinal lavage detergent.

Indigo carmine removal by charcoal from rice bran as an agricultural by-product

On the utilization of agricultural by-product, charcoal from rice bran was produced. The adsorption characteristics of indigo carmine onto charcoals from rice bran were investigated by the batch method. The yield and surface area of charcoal were decreased and increased with increase of carbonization temperature, respectively. The removal ratio of indigo carmine was high with the charcoal carbonized at higher temperature. In the relationship between the amount of indigo carmine adsorbed and the square root of elapsed time, a good linearity was recognized. The kinetic constant of adsorption removal for indigo carmine was rapid in the charcoal carbonized at higher temperature. The adsorption characteristics for indigo carmine removal by charcoal from rice bran were dominated by the value of their surface area.

Inhibitory effect of sorbitol on acetaminophen adsorption by activated carbon.

ABSTRACT The effective use of activated carbon as oral adsorbent in the primary treatment of acute acetaminophen poisoning was studied. The adsorption characteristics of acetaminophen onto activated carbons in presence of sorbitol were investigated in vitro. Both the equilibrium amount adsorbed and the removal rate of acetaminophen onto activated carbon were decreased with the increase of sorbitol concentration in solutions. The sorbitol concentration independency of the inhibition to the acetaminophen adsorption was recognized. It was concluded that the addition of sorbitol to the suspension of activated carbon inhibited the acetaminophen adsorption by activated carbon.

Hydrogen sulfide removal by iron containing activated carbon

Activated carbon modified by impregnation with iron (III) chloride solution (Fe‐ACs) were studied to try to raise their adsorption capacity for hydrogen sulfide, a malodorous substance. The surface area and pore volume of activated carbon were decreased by impregnation, but the amount of hydrogen sulfide adsorbed onto Fe‐AC was larger than that onto raw activated carbon (R‐AC). In particular, a large increase of the amount adsorbed onto Fe‐AC was noted at low equilibrium pressure. It was assumed that the increase of amount of hydrogen sulfide adsorbed onto Fe‐AC was due to the chemical interaction between iron (III) chloride on the pores in addition to the physical adsorption onto pores of activated carbon. Fe‐AC shows a high selectivity for hydrogen sulfide.

Recovery of molybdenum from fly ash by gibbsite

The effectiveness of gibbsite (GB), an amorphous aluminum oxide, for the recovery of Mo(VI) from eluates of fly ash of two coal-fired thermal power stations and of roof tile waste was investigated. Upon the qualitative analysis of an eluate of fly ash, 16 elements were detected. Greater amounts of these elements were eluted under acidic conditions (pH 2) than from the neutral or basic eluate of fly ash. GB was used for the adsorption of Mo(VI). Equilibrium adsorption was reached within 1 min. Optimal solution acidity for the adsorption of Mo(VI) onto GB400 (calcined at 400°C) was pH 2. The main adsorption mechanism was ion exchange with a number of hydroxyl groups of GB400. For repeated ad- and desorption of Mo(VI), GB400 could be used at least four times and the recovery percentage of Mo(VI) with sodium hydroxide solution as eluent surpassed 90%. Our results showed that GB400 was very effective for the recovery of Mo(VI) from fly ash.