NOVELTY - Preparing bismuth(III) carbonate photocatalyst, comprises adding sodium carbonate in a beaker, adding distilled water in volumetric flask with a glass rod to obtain 0.1 mole/l of sodium carbonate solution, adding de-ionized water in a small clean beaker, heating the de-ionized water, adding bismuth(III) nitrate pentahydrate in the beaker, stirring and dissolving, concentrating using nitric acid, adding 0.1 mole/l of sodium hydroxide solution, then stirring for 3 hours, filtering, collecting white precipitate, adding de-ionized water to wash for 2-3 times, and then drying at 80 degrees C.    USE - The method is useful for preparing bismuth(III) carbonate photocatalyst to treat pollution in sewage (all claimed).    DETAILED DESCRIPTION - Preparing bismuth(III) carbonate photocatalyst, comprises adding 0.01 mole of sodium carbonate in a beaker, adding 100 ml of distilled water in 40 ml of volumetric flask with a glass rod for 2-3 times to obtain 0.1 mole/l of sodium carbonate solution, adding 20 ml of de-ionized water in a small clean beaker, heating the de-ionized water in a water bath at 60 degrees C, adding bismuth(III) nitrate pentahydrate in the beaker, stirring and dissolving, concentrating using 0.1 mole/l of nitric acid to adjust pH value to 0.8, adding 0.1 mole/l of sodium hydroxide solution by adjusting pH value to 8, then stirring for 3 hours, filtering, collecting white precipitate, adding de-ionized water to wash for 2-3 times, and then drying at 80 degrees C. INDEPENDENT CLAIMS are included for:    (1) measuring degradation rate of sewage using bismuth(III) carbonate photocatalyst, comprising adding 0.01 g of methylorange in distilled water in 1000 ml of volumetric container with a glass rod, dissolving for 3-5 times, washing the volumetric flask by dropping water until the liquid level reaches 1000 ml in a scale line, concentrating 10 mg/l of methylorange to obtain methylorange solution, adding 0.01 g of methylene blue in distilled water in 1000 ml of volumetric container with a glass rod, dissolving for 3-5 times, washing the volumetric flask by dropping water until the liquid level reaches 1000 ml in a scale line, concentrating 10 mg/l of methylene blue to obtain methylene blue solution, adding 0.01 g of phenol in distilled water in 800 ml of volumetric container with a glass rod, dissolving for 3-5 times, washing the volumetric flask by dropping water until the liquid level reaches 1000 ml in a scale line, concentrating 10 mg/l of phenol to obtain phenol solution, adding 10 mg/l of methylorange solution, methylene blue solution, and phenol solution in three clean tube, adding bismuth oxychloride into 0.2 g of sodium bicarbonate in the clean tube, photo-chemically reacting the solution under continuous agitation for 30 minutes, sampling and measuring absorbance A1, passing visible light for two hours, again sampling and measuring absorbance A2, calculating absorbance A1 and A2 as given in the specification, where methyl orange solution has a wavelength of 464nm, methylene blue solution has a wavelength of 662 nm, and a phenol solution has a wavelength of 510 nm, again adding 10 mg/l of methylorange solution, methylene blue solution, and phenol solution in six clean tube, respectively weighing 0.05 g of bismuth(III) carbonate in degradation pipe, adding 0.05 g of titanium dioxide in the degradation in pipe, performing photo-chemical reaction, then dark reaction under continuous agitation for 30 minutes, sampling and measuring the absorbance-A1, continuously stirring under UV light for 1 hour, sampling and measuring absorbance-A2, calculating degradation as given in the specification, centrifuging obtained sample into double-beam UV TU-1901 spectrophotometer and a visible spectrophotometer for measuring the anti-UV liquid phase performance for 20 minutes, recording obtained data, then adding 0.2 g of sodium bicarbonate and titanium dioxide in the degradation pipe, measuring the fluorescent property, again adding 10 mg/l of methylorange solution, 20 mg/l of methylene blue solution, 40 mg/l of phenol solution, 0.004 g of ammonium oxalate, 0.004 g of parabenzoquinone, 0.0038 ml of catalase, and PTFE in a small magnetically stirring apparatus, and reacting for 30 minutes; and    (2) degrading the sewage, comprising adding 0.2000 g of bismuth(III) carbonate into the a degradation branch pipe, adding PTFE in a small magnetic stirring apparatus, then placing in a XPA series photo-chemical reaction tube under the continuously stirring condition, processing for 30 minutes, centrifugally separation the sample, measuring the initial chemical oxygen demand (COD), biochemical oxygen demand (BOD), ammoniacal nitrogen, and chromaticity using 350 W high pressure xenon lamp, and then centrifugally separating sampling, and measuring terminal removal rate.