Anions in wastewaters - Determination of Anions in Natural and Treated Waters - page 525

Table 8.1 Recovery of boron from real samples spiked at 20mg L −1

Sample description* Colour/ Hazen

units mg L −1

Boron concn.
in sample %

Recovery
100 ±5%

Significance†

Clean river water 1 200 <0.1 106.1 N.S.

Clean river water 2 70 <0.1 103.7 N.S.

Clean peaty stream water 500 <0.1 101.5 N.S.

Good sewage effluent 40 0.89 103.3 N.S.

Poor sewage effluent 60 0.74 99.6 N.S.

Septic tank effluent 40 1.45 99.4 N.S.

industrial makings effluent 500 <0.1 102.1 N.S.

Detergent manufacture
effluent

50 0.16 104.4 N.S.

Surface water from
detergent manufacture

30 0.64 99.7 N.S.

Poor petrochemical
treatment plant effluent

50 0.25 109.8 S.

*See Table 8.2
†N.S.=not significant at 95% confidence level. S=significant at 95% confidence level
Source: Reproduced with permission from the Royal Society of Chemistry [7]

exceeding 40°C) for 1h. Allow the azo-methine-H to settle for 16h. Centrifuge and
discard the supernatant liquid, slurry the residue with ethanol and filter through a
Whatman grade C glass-fibre filter paper. Dry at 105 °C for 3h and store in a desiccator.
The yield of azomethine-H should be approximately 18g.
Dissolve 900 ± 10mg of azomethine-H and 2g of L-ascorbic acid in 70ml of water
while heating gently (not exceeding 70°C) and dilute to 100ml. Add 100ml of buffer
solution and mix thoroughly. The reagent is stable for 2 days only. The solution without
buffer will keep for 14 days provided that it is filtered prior to use.
Buffer solution: Dilute 500ml of glacial acetic acid to 750ml with water. Add 10g of
EDTA and 300g of ammonium acetate and warm to dissolve. Adjust to pH 5.2 ± 0.1 with
acetic acid or ammonia solution if necessary. Add 1ml 1% Brij 35, polyoxyethylene
lauryl ether). Absorbance occurs over a wide peak at 410-420nm, and was linear over the
range 0-4mg L −1 of borate.
Determination of boron in a range of raw waters and sewage effluents was found to be
satisfactory relative to the standard carmine method [8], which involves destruction of
organic matter at 500°C. The river waters tested gave a mean of 0.2mg L −1 with a
recovery of 105.3% relative to the standard method and the effluents gave a mean of
1.3mg L −1 with a relative recovery of 102.9% (Table 8.1).