BORON REMOVAL FROM INDUSTRIAL WASTE WATERS BY USING ALUMINUM NITRATE COAGULANT WITH CHEMICAL COAGULATION METHOD
摘要：In this study, removal of boron from the industrial waste waters by chemical coagulation methods and effecting parameters of the process has been investigated by using aluminum nitrate（Al（NO3）3） as coagulant. The effects of initial pH of solution, initial boron concentration, stirring speed, dosage of the coagulant substance were investigated for boron removal. It is observed that stirring speed isn’t affected in the boron removal efficiency. The rapid stirring speed of 120 rpm and the low stirring speed of 30 rpm were used in experiments as stirring speed. It is observed that pH is the most important parameters for boron removal by chemical coagulation process. It is observed that the boron removal efficiency is the highest when the different coagulant dosage was applied and the last pH’ s of solution were values between 7-9. The reason of this, the pH of Al（OH）3 formation is high in values between 6.0-9.0. Increasing in the initial boron concentration increased the boron removal efficiency. A large amount of aluminum in the media is in the form of Al（OH）3 at this pH range and the type of this form does tend to make flocks. According to the accomplished results, it has been believed that increasing the treatment efficiency was depended on the sufficient coagulant and the pH at which dissolving of aluminum is the lowest. The solid Al（OH）3（s） dissolves at lower and upper values of this pH region and stays as dissolvable aluminum forms. Instead of aluminum ions were presented in the medium, they did not intent to make flocks at out of these pH regions. When distribution of different borate ions which were generated depending on the pH in aqueous boron solutions borate is examined, boron ions were found as polyborates at lower pH and monoborates at higher pH. When the pH of the medium is higher than 8 then generally the boron ions were found in the form of B（OH）4-.When experimental results were examined the flocks of Al（OH）3（s） which were formed at the above mentioned pH region could remove the boron in the medium, efficiency of the removal stays at low rates due to deficient flock generation at lower and upper variations of pH. It has been observed in all completed experiments that the maximum removal rate was found 35%.
Sixteenth International Water Technology Conference