Removal Of Heavy Metals From Acid Drainage By Pig Bone Meal

Heavy metal pollution issue is always receiving many public concerns.One of the main heavy metal pollution sources is the acid mineral drainage(AMD),which comes from the exploitation activities of mineral resources.Heavy metal ions not only pollute water and soil,but also threaten food safety and human health.Therefore,appropriate method to treat it is of great importance.Pig bones are commonly treated as kitchen waste.Many pig bones are generated during the consumption of meat in China.A large portion of those bones are scrapped directly as kitchen waste.If pig bones,which are relative cheap and easy to be attained,can be used in the treatment of AMD,heavy metal can be treated and a new approach for the multi-purpose utilization of pig bones can be identified.In this study,pig bones are used as experimental objective.Via a serious of static adsorption experiments and isotherm adsorption experiment,removal effect of PBM is acquainted.In order to know the equilibrium time of the adsorption reaction,keep close tracking on the adsorption process by taking samples at different time according to the experimental design.Furthermore,kinetic adsorption experiment that can provide theoretical support for the actual project(if any)is also conducted in this study.Main results of this study can be referred as below:1.Obvious difference between PBM samples(before and after heavy metal adsorption)can be identified easily by SEM and EDX characterization analysis.Before adsorption,small pores and irregular particles can be found randomly on the smooth surface of PBM.While after heavy metal adsorption,lamellar,sheet and bar like crystal substance,which are mainly consisted of corresponding metallic phosphate,can be found on the surface of PBM;and organic components disappeared after adsorption.2.The effects generated by absorbent quantity,absorbent particle size and p H are checked and considered in this dissertation.Experiment results show that there is an obvious positive effect from absorbent quantity / absorbent size;meanwhile,there is no significant positive effect on the removal efficiency with the increase of p H,as long as the heavy metal ions are not precipitating.From the result of adsorption isotherm experiment,adsorption process for PBM is more complied with Langmuir adsorption isotherm equation.For PBM(Particle size 0.2-0.3mm),the maximum adsorption quantity of Cd2+ is 44.56 mg g-1,66.12 mg g-1 for Cu2+ and 120.89 mg g-1 for Pb2+ at 298 K according to Langmuir adsorption isotherm module.This result can also be verified by the experiment data.3.From the tracking result of adsorption effect,at 298 K,concentrations of Cd2+,Cu2+,Pb2+ decrease very quickly during the first 4hrs.And after,the adsorption will reach its balance slowly in about 140 hrs.At 298 K,the adsorption process of PBM is much more complied with pseudo-second-order adsorption kinetics when analyzed by data fitting.Therefore,it is positive correlation between adsorption rate for PBM and the square of driven force.4.In the simulated experiment of removing heavy metal Cd2+ by a fixed bed of pig bone meal,the decrease of flow rate,increase of the height of fixed bed and the reduction of particle size of PBM will be beneficial to prolonging the adsorption breakthrough time.Since AMD contains a large amount of Fe3+ ions,yellow precipitation can be formed during the treating of AMD.