Novel Coagulant Preparation And Application In Printing And Dyeing Wastewater Treatment

Printing and dyeing wastewater mostly derives from processing procedures aspretreatment,dyeing and printing. It is very difficult to treat this kind of wastewaterbecause of its complex ingredients, high organic matter-containing and so on.Coagulation process is a primary method to treat dyeing and printing wastewater,and the utilization of a suitable coagulant is very important to the treating effect.Coagulants include inorganic and organic coagulants, while the former is much morepopularly used than the latter.A series of high-effective and economic coagulants using an abundant waste slagwere developed according to character of this wastewater. The preparation methodwas introduced in detail in this article.The 1# Bs coagulant was prepared and applied to two kinds of typical dyeing andprinting wastewater (type A and type B). The results show that this coagulant workswell.Type A is a kind of wastewater with low colority and low chemical oxygendemand (COD), which also contains a lot of suspension matter, The 1# Bs coagulantwas prepared during experiments. And the optimal reaction conditions are: pH value11, reaction during 3 min, coagulant dosage 7.0g/L. More than 55% COD and 95%colority removal were observed.Type B is a kind of wastewater with high colority and low COD, and it alsocontains much suspension matter. The optimal conditions of reacting with 1# Bscoagulant are: pH value 11, reaction during 4 min, coagulant dosage 10.0g/L, and theresults show that more than 74% COD and 98% colority are removed.The 2# Bs coagulant was prepared for the dyeing wastewater with high COD andhigh colority. The optimal coagulation conditions are: pH value 11, reaction during 4min, coagulant dosage 8.0g/L. More than 91% COD and 99% colority removal wereobserved. The effluent after the treating process reaches the standard stipulated by thenational regulations.It is concluded from the above mentioned experimental results that Bs series icoagulants are much more economic and effective compared to other test inorganiccoagulants. It also proves that using waste can control waste.Based on the experiments, the mechanism of coagulation was also postulated.The coagulation effect is mainly produced through the compression of thedouble-layer and the charge neutrality by the addition of Mg2+ and Fe3+ cations. It wasfound that the removal of COD and colority was also improved by the slag pre-treatedby the acid. Adsorption of the formed colloid on the slag surface covered with lots ofholes accelerated the sedimentation.The self-developed BS series coagulants are effective, economic, easy to beprepared, and feasible to actual printing and dyeing wastewater treatment.