Resource Utilization Of Pyrite Wastewater And Sludge From Pyrite Wastewater Treatment

The pyrite wastewater which is produced during or after the iron pyrite exploitation contains lots of iron and shows high acidity. The sludge from pyrite wastewater treatment by neutralization method is a kind of iron-rich sludge. The resource utilization of pyrite wastewater and its sludge has important significance on elimination of environmental pollution and recovery of iron resource.In our study, the process feasibility and optimal conditions of nanometer black iron oxide pigment preparation from pyrite wastewater and PFS preparation with sludge from pyrite wastewater treatment were explored.The pyrite wastewater which was pretreated to remove aluminum was utilized as ferrous source and a certain amount of FeCl3·6H2O was added to it as ferric source to prepare nanometer black iron oxide pigment by co-precipitation method. Nanometer black iron oxide pigments with satisfactory quality can be obtained under the optimal process conditions: nFe3+/nFe2+1.9, reaction temperature 55℃, original pH of reaction solution 8.5, reaction time 40 min. XRD, SEM and black iron oxide pigments qualification analysis showed that the particle size of the prepared black iron oxide pigment was about 16.6 nm,and Fe3O4 content was higher than 90%. The product can attain the first-grade standard in black iron oxide pigment industry. On the basic of optimal process conditions, high tinting strength black iron oxide pigment can be prepared under the following conditions: stirring rate 250 r/min, mass concentration of precipitant NaOH 7.5%, dosing quantity of dispersants citric acid(mass concentration 1%) 1 mL. XRD and SEM analysis showed that the agglomeration was obviously improved, the size of particle was in a little decrease.The mixed solution(volume ratio of pyrite wastewater and sulfuric acid 9:1) was used to extract iron from sludge. The high extraction rate can be obtained under the following conditions: volume/mass ratio of acid solution and dried sludge 3.4:1, acid dissolving time 15 min, acid dissolving temperature 65℃. The extracted solution pre-treated by centrifugation was used in oxidative polymerization process to prepare PFS. The high quality PFS can be obtained under the following conditions: original pH of reaction solution 0.9, reaction temperature 40℃, reaction time 2 h, oxidant dosage 2 times to the theoretical amount. The coagulation and sedimentation effect of self-made PFS on the printing and dyeing wastewater can totally reach the saled PFS grade.