Development of facile field-test paper for rapid determination of iron contamination in natural water of acid sulfate soils

Abstract

The iron concentration in natural water of acid sulfate soils is usually determined by complicated methods of SMEWW 3111B:2017 or ISO 6332: 1988 E in the laboratory for acidified water samples at pH ∼2–3. Therefore, the rapid field determination of iron content in natural water is a very useful method because it limits the error and reduces the experimental time for analysis. In this study, we proposed, developed, and tested a rapid colorimetric analysis method based on the chemical reaction of ferric and anion thiocyanate (SCN−) ions for an iron concentration range of 0–100 mg/L with a linear equation of ΔE = 0.5955x + 2.0909 and high correlation coefficient (R2) of 0.9864. The results from 10 water samples by this method were very close to those by flame absorption spectroscopy with a difference of less than 5%. Besides the biggest advantage of rapid site testing, this method also gives quite high accuracy compared to the molecular absorption method of ISO 6332:1988 E. In addition, this new method can quantify Fe3+, Fe2+, and total iron in water, suggesting a very useful and potential method for determining the iron content of natural water from acid sulfate soils. HIGHLIGHTS A color chart was developed to determine iron in water using indicator paper.; A linearity of the iron content was obtained with a concentration below 100 mg/L.; The method gives relatively fast and accurate results of Fe2+, Fe3+, and total iron.; The tested results show high accuracy and sensitivity in natural iron alum water.;

Keywords

• acid sulfate soil
• color chart range
• colorimetric analysis
• iron analysis
• test kit