| Because of staying in formation for long time, the content of calcium and magnesium increase. In the process of washing, calcium and magnesium can influence the washing efficiency by interacting with surfactants. The washing efficiency of several detergents has been researched in hard water. In the water hardness of 100 mg/L, standard detergent has a cleaning rate of 34.87%, OMO has a cleaning rate of 30.74%, Diaopai soap powder has a cleaning rate of 30.14%. When the water hardness increases to 600 mg/L, the cleaning rate of OMO detergent has decreased to 13.62%, however Diaopai soap powder can also has a cleaning rate of 20.51%. The results show that Diaopai soap powder has better performance than OMO detergent in high water hardness.The interaction of surfactants and builders with calcium ion has been studied. The concentration of calcium is 5.5×10-4 mol/L, after soaking in the solution of 0.022% surfactants, the concentration of calcium decreases less in AES than in LAS, which shows that LAS have more ability to compound with calcium than AES. STPP and 4A zeolite solution has been soaked in calcium solution for 1 h, 0.02% STPP can almost bind all calcium ion, but in 0.03% 4A zeolite the calcium ion can also been detected. This can explain that the binding ability of STPP to calcium is better than 4A zeolite. When soiled cloth has been soaked in the solution, the concentration of calcium has decreased. This is because the calcium has been absorbed in the fabric. The detergency of surfactants and builders has been researched, the proportion of surfactant is 12%. When the addition of STPP is 15%, the cleaning rate is 29.10, when 20% 4A zeolite has been added into the solutions, the cleaning rate is 28.02%. This can show that STPP has better assisting washing performance than 4A zeolite. AEO9 has better detergency than LAS and AES. When there is no builder, the washing performance of AES is better than LAS, when builder was added into the solution, the washing performance of LAS has excessed AES, which shows that AES has better performance of resisting hard water than LAS.Citric amide has been prepared using citric acid and monothanolamine as starting materials. The influence of time, temperature and material ratio to the reaction has been investigated. From orthogonal experiments we have got the best reaction conditions. The reaction time is 3h, reaction temperature is 150℃, ratio of citric acid to monothanolamine is 1:1.2. The structure of the product was demonstrated by IR characterization. The chelating property of citric amide is discussed in different time and temperature. The maximum chelating amount in 20℃is 368 mgCaCO3/g. When the temperature rises to 60℃, the chelating amount of calcium has decreased to below 100 mgCaCO3/g.The product has been added into heavy-duty liquid detergent, the cleaning rate of the detergent is higher than 30.00% when water hardness is below 300 mg/L. When the addition amount of citric amide is 20%, the cleaning rate is 35.30%, but the detergency can not improve significantly when the addition of builder is increased.
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