| The water shortage and pollution seriously threaten the people's life and sustainable development of economy.Currently,as the major water users,the annual discharge of mineral processing wastewater is 200m tonnes.The mineral processing wastewater contains fine tailing particles,heavy metal ions and flotation reagents,its direct discharge would cause the environmental pollution as well as a great waste of water resources.However,if directly recycled,the fine particles and heavy metal ions would lead to the deterioration of flotation indexes and reduce the economic benefit of mineral processing industry.Therefore,the mineral processing wastewater efficiently treated could be recycled and ensure the normal and stable index of production,which has great economic,environmental and social significance.In this study,the hybrid materials,showing a "star-like" structure that an organic nano-particle acts as core linking polymer arm chains,have been prepared.In the hybrid material,the inorganic and organic components are well mixed and act synergistically to remove fine particles and heavy metal ions rapidly and efficiently in mineral processing wastewater.The mineral processing wastewater efficiently treated could be reused and ensure the normal and stable index of production.The main works and results are as follows:Cyanide tailing suspension was selected as the flocculation object,the main component of particles in which was gangue,and thus the specific density of particles was low.In addition,the particles were fine with an average size of 30 ?m and negatively-charged with a ? potential of-5.26 mV So the particles settled slowly by gravity from cyanide tailing suspensios.In view of this,an hybrid material Al-PAM was synthesized with a "star-like" structure that Al(OH)3 colloids acts as cores linking polyacrylamide arm chains.The Al-PAM served as flocculant for the cyanide tailing suspensions,the flocctant GG was used for comparison.The flocculation experiments indicated that Al-PAM increased the initial settling rate of particles by 18.5 times of blank without flocculants,and the turbidity removal efficiency of supernatant by Al-PAM was 98.5%.Meanwhile,Al-PAM achieved the equivalent effect at lower addition of 0.5 mg/L with GG at its optimum dosage of 4 mg/L.When used in the cyanide tailing suspensions with average particle size of 30 ?m,14 ?m and 3 ?m respectively,Al-PAM all performed better than PAM.What's more,the much fine the particles were,the more superior Al-PAM performed.Therefore,the Al(OH)3 colloids in Al-PAM played a significant role in flocculation of negatively-charged fine particles.The excellent performance of Al-PAM could be attributed to the charge neutralization of Al(OH)3 colloids and bridge adsorption of extended PAM chains.Considering the flocculation advantage of inorganic-organic polymer Al-PAM for fine particles,the cationic hybid copolymer Al-P(AM-DMDAAC)was obtained through the copolymerization of acylamide and dimethyldiallylammonium chloride onto the surface of Al(OH)3 colloidal paticles,in order to effectively flocculate the fine particles with high negative surface charge.The flocculation sample was silica suspensions,the partilces in which had an average size of 5 ?m and high ? potential of-27.46 mV.The Al-PAM was also investigated in silica suspensions for comparison.The results showed that Al-P(AM-DMDAAC)reduced the supernatant turbidity of silica suspensions to 9.066 NTU from 50000 NTU in blank experiment.However,Al-PAM which had a similar molecular weight with Al-P(AM-DMDAAC)just reduced the supernatant turbidity to 2032 NTU.The charge neutralizing ability of Al-P(AM-DMDAAC)was obviously improved compared with Al-PAM(? potential increased by 3?6 times),which indicated that charge neutralizing ability is a significant parameter in determining the performance of flocculants for the removal of fine particles with high negative surface charge.The adsorbent Al-PAM-DTC was successfully synthesized by grafting dithiocarbamate onto the "star-like" hybrid structure of Al-PAM for efficient removal of heavy metal ions in mineral processing wastewater.The maximum adsorption capacities of Al-PAM-DTC for Cu2+ and Pb2+ were 416.959 mg/g and 892.505 mg/g,respectively.Al-PAM-DTC was able to remove above 97%of positively-charged bauxite particles as well as 97%of Cu2+ or Pb2+ simultaneously through flocculation and chelation in the binary systems containing fine particles and heavy metal ions.However,the removal efficiency of negatively-charged partilcles by Al-PAM-DTC was only 85%.Chemisorption was the adsorption mechanism of Al-PAM-DTC for Cu2+ and Pb2+,which was attributed to the chelation of nitrogen-containing,oxygen-containing and xanthate functional groups with metal ions.In view of the weak flocculation of Al-PAM-DTC for negatively-charged particles,the DTC was grafted onto the hybrid copolymer Al-P(AM-DMDAAC)to obtain Al-P(AM-DMDAAC)-DTC in order to neutralize the negative charge of DTCs by cationic DMDAAC.Al-P(AM-DMDAAC)-DTC performs better in the coexisting system of negatively-charged silica particles and heavy metal ions,achieving more than 97%of turbidity removal and 90%of Cu2+ or Pb2+ removal.The saturated adsorption capacities of Al-P(AM-DMDAAC)-DTC for Cu2+ and Pb2+ were 317.777 mg/g and 586.699 mg/g,respectively.Al-PAM-DTC was further used for the adsorption of MB to investigate the adsorption potential of functional chelation groups for dyes.Al-PAM-DTC could quickly and efficiently remove more than 98%of MB from 50mg/L of the synthetic dye wastewater within 30 min.In addition,it demonstrated much higher MB adsorption capacity of 1088.55 mg/g than any other reported synthetic materials,and thus could be used for effective treatment of dyes wastewater.The MB adsorption was a spontaneous and exothermic process,and the chemisorption mechanism could be attributed to the electrostatic attraction and coordination of nitrogen-containing,oxygen-containing and xanthate functional groups with dyes. |
PDF Full Text Request