Tsunenori Nakajima

Adsorption and removal of arsenic(V) from drinking water by aluminum-loaded Shirasu-zeolite

The demand for effective and inexpensive adsorbents is to increase in response to the widespread recognition of the deleterious health effects of arsenic exposure through drinking water. A novel adsorbent, aluminum-loaded Shirasu-zeolite P1 (Al-SZP1), was prepared and employed for the adsorption and removal of arsenic(V) (As(V)) ion from aqueous system. The process of adsorption follows first-order kinetics and the adsorption behavior is fitted with a Freundlich isotherm. The adsorption of As(V) is slightly dependent on the initial pH over a wide range (3-10). Al-SZP1 was found with a high As(V) adsorption ability, equivalent to that of activated alumina, and seems to be especially suitable for removal of As(V) in low concentration. The addition of arsenite, chloride, nitrate, sulfate, chromate, and acetate ions hardly affected the As(V) adsorption, whereas the coexisting phosphate greatly interfered with the adsorption. The adsorption mechanism is supposed as a ligand-exchange process between As(V) ions and the hydroxide groups present on the surface of Al-SZP1. The adsorbed As(V) ions were desorbed effectively by a 40 mM NaOH solution. Continuous operation was demonstrated in a column packed with Al-SZP1. The feasibility of this technique to practical utilization was also assessed by adsorption/desorption multiple cycles with in situ desorption/regeneration operation.

Studies on the accumulation and transformation of arsenic in freshwater organisms I. Accumulation, transformation and toxicity of arsenic compounds on the Japanese Medaka, Oryzias latipes

Accumulation, transformation and toxicity of arsenic compounds to Japanese Medaka, Oryzias latipes were investigated. For sodium arsenite [As(II)] and disodium arsenate [As(V)], the mean value for 7-day lethal concentration LC50 for O. latipes were 14.6 and 30.3 mg As/l, respectively. Direct accumulation of arsenic in O. latipes increased as a function of As(III) concentration in water. A small proportion of accumulated arsenic was transformed to methylated arsenic. As much as 70% of the total arsenic accumulated in tissue was depurated. Accumulation and transformation of As(III) by O. latipes in a simple freshwater food chain were also investigated. The transformation of As(III) to As(V) by organisms was more prevalent than biomethylation of accumulated arsenic in organisms of the three steps of the food chain.

Studies on the accumulation and transformation of arsenic in freshwater organisms II. Accumulation and transformation of arsenic compounds by Tilapia mossambica

Bioaccumulation and biotransformation of arsenic (As) compounds in freshwater Tilapia mossambica was investigated. The direct accumulation of As by T mossambica was proportional to the concentration of arsenicals in water. Small amounts of accumulated As were transformed to methylated As, including trimethylarsenic (TMA) species. Accumulation and transformation of As(III) by T. mossambica via freshwater food chain results in the transformation of As(III) to As(V) with little biomethylation of accumulated As. Approximately 90% of accumulated As was depurated to water.

Determination of trace elements in coal and coal fly ash by joint-use of ICP-AES and atomic absorption spectrometry

Microwave-acid digestion (MW-AD) followed by inductively coupled plasma-atomic emission spectrometry (ICP-AES), graphite furnace atomic absorption spectrometry (GFAAS), and hydride generation atomic absorption spectrometry (HGAAS) were examined for the determination of various elements in coal and coal fly ash (CFA). Eight certified reference materials (four coal samples and four CFA samples) were tested. The 10 elements (As, Be, Cd, Co, Cr, Mn, Ni, Pb, Sb, and Se), which are described in the Clean Air Act Amendments (CAAA), were especially considered. For coal, the HF-free MW-AD followed by ICP-AES was successful in the determination of various elements except for As, Be, Cd, Sb, and Se. These elements (except for Sb) were well-determined by use of GFAAS (Be and Cd) and HGAAS (As and Se). For CFA, the addition of HF in the digestion acid mixture was needed for the determination of elements, except for As, Sb, and Se, for which the HF-free MW-AD was applicable. The use of GFAAS (Be and Cd) or HGAAS (Sb and Se) resulted in the successful determination of the elements for which ICP-AES did not work well. The protocol for the determination of the 10 elements in coal and CFA by MW-AD followed by the joint-use of ICP-AES, GFAAS, and HGAAS was established.

Arsenic speciation in marine product samples: Comparison of extraction–HPLC method and digestion–cryogenic trap method

For the arsenic speciation in marine product samples, two types of pretreatment-analysis combination were compared. One is the combination of solvent extraction and high performance liquid chromatography (HPLC) followed by a highly sensitive arsenic detection, while the other is the combination of alkaline digestion and cryogenic trap (CT) method followed by a highly sensitive arsenic detection. For six certified reference materials (CRMs) of marine animal samples, the concentrations of arsenobetaine (AsB) obtained from the extraction-HPLC method were very consistent with those of trimethylated arsenic species measured by the digestion-CT method. For four seaweed samples, the determination of three arsenosugars (Sugar-1, Sugar-2, and Sugar-3) was favorably carried out by the extraction-HPLC method. Those seaweed samples were also subjected to the digestion-CT method, and the amounts of dimethylated arsenic species measured by the method were approximately equal to the sum of the amounts of dimethylarsinic acid (DMAA) and three arsenosugars (Sugar-1+Sugar-2+Sugar-3) obtained from the extraction-HPLC method.

Leaching of arsenic from coal fly ashes 1. leaching behavior of arsenic and mechanism study

The leaching of arsenic from coal fly ash NIST‐1633b and NIST‐2689 was tried with various lixiviants. The leaching of arsenic was found to have taken place readily and to be dependent on both the equilibria of dissolution/precipitation and adsorption/desorption in the leaching system. The arsenic leaching intensity was significantly elevated by the use of proper chelating agents, which is supposed to be owing to the formation of metal (aluminium and/or iron)‐chelate complexes followed by an enhanced binding with arsenate ions. The results of the present study show that arsenic oxides are associated well with iron and aluminium oxide deposits on the particle surface of coal fly ash NIST‐1633b. Surface enrichment for arsenic was also examined and confirmed by XPS measurement. The leaching percentages of arsenic on the surface from XPS detection were in good agreement with those in bulk found in the leaching tests.

Determination of total arsenic in coal and wood using oxygen flask combustion method followed by hydride generation atomic absorption spectrometry.

A simple and sensitive procedure for the determination of total arsenic in coal and wood was conducted by use of oxygen flask combustion (OFC) followed by hydride generation atomic absorption spectrometry (HGAAS). The effect of various items (composition of absorbent, standing time between the combustion and filtration, particle size and mass of sample) was investigated. Under the optimized conditions of the OFC method, nine certified reference materials were analyzed, and the values of arsenic concentration obtained by this method were in good accordance with the certified values. The limit of detection (LOD) and relative standard deviation (RSD) of the method were 0.29 microg g(-1) and less than 8%, respectively. In addition, eight kinds of coals and four chromated copper arsenate (CCA)-treated wood wastes were analyzed by the present method, and the data were compared to those from the microwave-acid digestion (MW-AD) method. The determination of arsenic in solid samples was discussed in terms of applicable scope and concentration range of arsenic.

Surveying the mutagenicity of tap water to elicit the effects of purification processes on Japanese tap water.

The mutagenicity levels of tap water in Japan were surveyed using the Ames test. Tap water samples (179) were collected at 17 sampling sites located from the northern tip (Hokkaido) to the southern tip (Kagoshima Prefecture). The mutagenicity values ranged from under the detection limit to 3600 net rev x L(-1). The average mutagenicity was 1100 net rev x L(-1) and the levels were significantly higher in the wintertime than in the summertime. The average mutagenicity of each site ranged from under the detection limit to 2000 net rev x L(-1). There was no significant correlation of the mutagenicity with TOC, A(260) or THMs. The highest positive ratios of the Ames test and the umu test were 92% under the condition TA100-S9 and 9% under the condition NM2009-S9, respectively, which indicated that the Ames test has higher sensitivity for the test of tap water than the umu test. This survey incorporated the 1992-1993 survey. The comparison of these survey-results in a further study will reveal the improvement of Japanese tap water quality from the perspective of mutagenicity.

Chlorination by-products of fenitrothion

The mutagens produced through chemical reaction between chlorine and the insecticide fenitrothion were studied by using a quadrupole GC-MS. The mutagenicity and the mutagen formation potential (MFP) of the identified by-products were evaluated by the Ames assay (preincubation method) using Salmonella typhimurium TA100 without exogenous activation by S9 mix (TA100-S9). Before conducting GC/MS analyses, six compounds were presumed to be produced in chlorinated fenitrothion. These compounds were confirmed to be produced by the GC/MS analyses, but none of them were mutagenic. One of the chlorination by-products, 3-methyl-4-nitrophenol, has 19 times greater MFP than that of fenitrothion. This result suggests that a major mutagen in chlorinated fenitrothion will be produced via a chemical reaction between chlorine and 3-methyl-4-nitrophenol.

Leaching of arsenic from coal fly ashes 2. Arsenic pre‐leaching with sodium gluconate solution

The present study deals with the development of an efficient and reliable process for safe disposal of coal fly ash to remove arsenic that has been found to be the most easily leachable and hazardous heavy metal in coal fly ash. Pre‐leaching of fly ash prior to disposal by a natural chelating agent, sodium gluconate (SG), was proposed and studied. Several operational factors influencing arsenic leachability, such as concentration of SG solution, liquid to solid ratio, pH, length of leaching time and leaching temperature were examined. Arsenic was found to leach out substantially with SG, but almost no further release was observed from the ash pre‐leached by SG. After the pre‐leaching treatment, the desirable high buffering capacity of the ash was well sustained. SG solution was effectively regenerated by activated alumina adsorption so that it could be successfully reused for multiple leaching/adsorption cycles.