Study On Thermosensitive Magnetic Absorbent Resin Preparation By Copolymerization And Fine Coal Dewatering

At present,the dewatering methods of fine coal,such as mechanical dewatering and mechanical combined dewatering method,are difficult to achieve the requirement that the moisture content of clean coal is reduced below 10%,and the method of thermal drying dewatering is high production cost,so fine coal dewatering is a formidable task in the industry of coal processing and utilization.Based on these reasons,using thermosensitive magnetic absorbent resin to remove the moisture of fine coal is proposed in this paper.Mixing the thermosensitive magnetic absorbent resin with fine coal to remove the moisture in fine coal and then separating the from the fine coal by magnetic separation method.At last,adsorbed water in thermosensitive magnetic absorbent resin is removed by non liquid-vapor phase transition using its temperature sensitivity to make the resin effective recovery and recycling.N-isopropylacrylamide is copolymerized with various monomers by adopting the method of the water solution free radical copolymerization,the influence factors,such as monomers、dosage of crosslinking agent、reaction temperatures、reaction times and dosage of sodium acrylate were investigated.The properties of the products like equilibrium swelling ratio 、 temperature sensitivity、swelling property、dewatering property and the water cycle load ratios were measured.At the same time,FTIR、XRD and TGA were used to analysis the structure and thermal stability of products.Experimental results indicate that the product have relative higher equilibrium swelling ratio（170.4g/g）、quick response temperature sensitivity（the point is about 50℃）、 fast swelling rate、rapid dewatering rate and maximum water cycle load ratio（161.6g/g）is synthesized under the conditions: the hydrophilic monomer is sodium acrylate、the molar ratio of sodium acrylate is 5%、the molar ratio of crosslinking agent is 3% 、the synthesis temperature is about 20 ℃ and the reaction time is about 12 hours.Thermosensitive magnetic absorbent resin was prepared by adopting the three step method.First,the magnetic Fe₃O₄ nanoparticles were prepared by co precipitation method,the influence factors,such as types of precipitation agent,reaction temperature and time were investigated,XRD 、 TEM and SQUID-VSM were used to analysis the structure and magnetism of products.The results of analyses show that the magnetic Fe₃O₄ nanoparticles which have complete crystal structure、no impurities、uniform particle size（about 14.1nm）、uniform particle dispersion 、 superparamagnetic and high ratio magnetic saturation intensity（about 69.70emu/g）can be synthesized under the conditions as follows: ammonia water is precipitant、synthesis temperature is 60 ℃ and crystallization aging time is 12 hours.Next,alcohol aqueous solution with volume ratio of 4:1 was employed to modify the surface properties of Fe₃O₄ and the results of FTIR and TGA suggest the surface modification was done.At length,the thermosensitive magnetic absorbent resin was prepared by suspension free radical polymerization,and the different forms of Fe₃O₄ addition and KH-570 content were investigated.Experimental results show that thermosensitive magnetic absorbent resin which have good bonding strength、relative higher equilibrium swelling ratio（94.6g/g）、quick response temperature sensitivity（the point is about 40℃）、fast swelling rate、 rapid dewatering and higher water cycle load ratio（91.1g/g）can be prepared when the dosage of KH-570 is 0.3mL.XRD、TGA、FTIR、SEM and SQUID-VSM were used to analysis the structure and performance of certain temperature sensitive magnetic absorbent resin,and the results showed that the magnetic absorbent resin was successful synthesized.The analysis of TGA show the addition of modified or original Fe₃O₄ could not affect the temperature of thermal decomposition and thermal stability of thermosensitive magnetic absorbent resin;the results of XRD indicate that the resin has no impact on crystal structure of Fe₃O₄;SEM showed that Fe₃O₄ is uniformly dispersed in the resin;the magnetic saturation intensity of thermosensitive magnetic absorbent resin is about 21.93emu/g.Thermosensitive magnetic absorbent resin was applied in the dewatering of fine coal and the effect of resin particle size、resin content、fine coal particle size and different fine coals on the dehydration were investigated.Experimental results show that the recovery of resin basically achieve to 100%.When the particle size of thermosensitive magnetic absorbent resin is 0.45⁰.3mm and the quality of the resin used relatively fine coal is 3%,the water content of the weakly caking coal with the initial moisture content of about 20% and the particle size of about 0.125 to 0.074 mm is reduced to less than 10%.Under the same conditions,the flame coal dropped from 26.84% to 17.11%.The water content of the three types of coal was reduced by about 10%.Temperature sensitive magnetic absorbent resin shows excellent dehydration efficiency.When the mixing time was extended to 150 min,the water of the three coal was slightly lower,while the water of the long flame did not fall below 10 percent,and this also suggests that long flame coal is relatively easy to dewater.