Browse Prior Art Database

A TECHNIQUE FOR NEAR CONTINUOUS MEASUREMENT OF AS ION CONCENTRATION IN WATER

IP.com Disclosure Number: IPCOM000007859D
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-Apr-30
Document File: 2 page(s) / 112K

Publishing Venue

Motorola

Related People

Eric S. Johnson: AUTHOR

Abstract

Water containing As waste is generated in many industrial processes, one of which is the fabrication of semiconductor devices from GaAs-related mate- rials. Industrial wastewater treatment plants are used to remove As and to permit the release of industrial water to municipal drains at As concentrations less than the legal maximum.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 50% of the total text.

Page 1 of 2

8 M-LA Technical Developments

A TECHNIQUE FOR NEAR CONTINUOUS MEASUREMENT OF AS ION CONCENTRATION IN WATER

by Eric S. Johnson

  Water containing As waste is generated in many industrial processes, one of which is the fabrication of semiconductor devices from GaAs-related mate- rials. Industrial wastewater treatment plants are used to remove As and to permit the release of industrial water to municipal drains at As concentrations less than the legal maximum.

  As concentrations in water are frequently meas- ured by introducing a representative water sample to a graphite firmace atomic absorption spectrome- ter. The concentration obtained in this manner is particularly accurate and uselit when the water mea.+ ured is taken from a holding tank. However, the technique will not suffice in the future. When pro- duction ramps up or the factory expands and the quantity ofwater to be treated increases, batch stor- age in holding tanks and batch treatment becomes increasingly burdensome. Another important issue in As treatment is that the legal release concentra- tion of As in water is being reduced, in some cases from 100 to 5 parts per billion (ppb). As-in-water measurement techniques giving rapid measurement with high sensitivity and reliability are needed. Such a technique would enable closed loop control of the flow rate of chemicals used to achieve As removal in the water treatment plant.

  Recent work by DeMenna et al.1 has demon- strated near continuous measurement ofAs concen- trations with ppb sensitivity. This is accomplished by converting the As ion in water to amine gas (ASH,) in a reaction cell. The arsine mixed with a carrier gas is input to a flame atomic absorption spectrom- eter (FAAS) with a near continuous analysis time of approximately one minute.

1G.J. DeMenna. K. Pealstrom and G. Brown. "Onti- mized analytical conditions for sub-ppb arsenic and selenium determinations by FAAS" American Envi- ronmental Laboratory, August, 1995.

  It is the purpose of this article to describe a fur- ther refinement which would also produce nearly continuous As concentration in water mreaurements and be highly reliable for field use. This refinement is to deliver the arsine gas produced by the reaction cell described by DeMenna to the input of a toxic gas monitor. The toxic gas monitor takes the place of the FAAS. An example of such a toxic gas moni- tor is the MDA model 7100, which detects arsine (and other hydrides) horn...