This paper presents a new way of recycling aluminum and iron in boiler slag derived from coal combustion plants for the production of a sulfate-based complex coagulant containing ferric sulfate and aluminum sulfate. The boiler slag sample was determined for more complete characterization by means of scanning electron microscopy(SEM), X-ray diffraction(XRD), X-ray fluorescence(XRF) and other techniques. An analysis for the boiler slag sample collected from Baotou Steel Plant located in Inner Mongolia, PR China showed that the quantity of iron and aluminum oxides, in general, accounted for about 35% of the boiler slag. XRD analysis indicates that predominate minerals such as kaolinite, quartz, calcium silicide, hematate and metakoalin exist in this boiler slag. This boiler salg was evaluated to determine the efficiency of converting the iron and aluminum components of the material into a sulfate-based complex coagulant when heated with sulfuric acid at different temperatures and reaction times. The maximum concentrations of Fe3+ and Al3+ in the complex coagulant prepared from the boiler slag were obtained at 130 and after 3 h of reaction time. These concentrations were 0.04 M Fe3+ and 0.46 M Al3+, respectively. The corresponding conversion efficiencies of aluminum and iron were 66.2 and 95.0% in the boiler slag, respectively. Finally, the prepared sulfate-based complex coagulant proved to be an effective agent for reducing the turbidity and chemical oxygen demand(COD) of a typical domestic sewage sample.

Combination of oven and microwave and only oven are two ways to study municipal sludge,and it investigates whether different size, microwave drying pretreatment, pretreatment time and oven temperature characteristics have effect on drying characteristics. The results shows that: using microwave to dry sludge need short time, the drying rate is fast, combination of oven and microwave has higher drying rate and lower energy consumption than only oven.

The objectives of this work are to study the influence of fluoride additives on aluminum recycling from the boiler slag. The effect of adding different amounts of fluoride, such as NaF, NH4F, KF and CaF2, was investigated. An elemental analysis of aqueous solutions leached by sulfuric acid and hydrochloric acid was determined by EDTA-Na2-ZnCl2 titration method. The components and microstructures of the samples were examined by means of XRF, XRD and SEM. Acid strength, leaching time, solid/liquid ratios and different additives were conducted in this experiment. The fluoride additives have a significant effect on the leachability of alumina in the boiler slag. NH4F is the best choice economically because of low dosage and high efficiency.

Sewage sludge treatment and disposal has become a hot issue of current environmental concern, not only its effect will cause secondary pollution to the environment, more importantly, a large quantity of sludge is produced and growth rapidly, acceptable urban area is limited. So its become an important issue need to be solved by us urgently. This article present the current domestic sewage sludge treatment and disposal methods respectively, elaborate the ways for utility, explain the practical advantages and disadvantages of each of these approaches and analyze the existing problems. At the same time, a number of resource utilization of new technologies was prospected.

The paper mainly targets at investigating municipal sludge drying technology which is efficient and economical. Use the oven, the microwave and the combination of both to study on the factors of the drying efficiency. The research found that the thinner sludge is easier to be dried, additionally, combining these two ways, which means to dry the sludge with dry box for a short time and then use the microwave to dry the sludge can greatly improve the drying efficiency. The research conclusions will provide a scientific basis for municipal sludge drying and semi-drying engineering practice, with some guiding significance.