分散剂对羟基磷灰石除氟剂制备的影响

Effects of Dispersant on Preparation of Hydroxyapatite for Fluoride Removal from Potable Water

羟基磷灰石(HAP)是经济高效且安全低碳的除氟剂,其制备时存在反应体系颗粒团聚板结导致产品性能不佳问题。该研究以熟石灰和磷酸为原料,采用加入分散剂的反向滴加化学沉淀法在常温下制备HAP除氟剂,探索分散剂对HAP制备的影响。结果表明:十二烷基苯磺酸钠(SDBS)/乙二醇组合为最佳分散剂,且SDBS、乙二醇和氢氧化钙的最佳质量比为1∶1∶1 000。在优化分散条件下,制得的产品除氟容量达16.56 mg/g,提高了32.90%。反应体系pH值随着氢氧化钙加入而不断升高,在105 min时达到最高值12.96,之后持续降低至8.13。OH-消耗速率与除氟量增加速率的比值先升高后降低,其在180 min时达到最大值4.98,在235 min后低于1.00。颗粒团聚粒径在60 min后持续减小,360 min时产品的d10、d_(50)和d_(90)分别为7.46、15.65和42.41μm,d_(50)和d_(90)较对照组分别降低了56.83%和52.21%。产品中HAP晶体呈纳米级,以团聚形式存在。产品能快速去除水中氟离子,符合拟二级动力学模型。

Hydroxyapatite(HAP)was the low-cost,efficiency,safe,and low-carbon defluorider for water treatment.It was often prepared with wet chemical precipitation process.However,the heavy aggregate and compaction arose during its prepa-ration,which resulted in the poor performance of products.In this study,the chemicals of Ca(OH)2,H3PO4 and dispersants were used to preparate HAP with the re-direction addition process.The effects of dispersant on the HAP preparation were in-vestigated.It was shown that sodium dodecyl benzene sulfonate(SDBS)/ethylene glycol were desirable dispersant for HAP preparation,and the optimized mass ratio of ethylene glycol,SDBS and Ca(OH)2 was 1∶1∶1000.With the optimized condi-tions of dispersant,the fluoride removal capacity of HAP product reached 16.56 mg/g,which increased by 32.90%.The pH value of reaction system increased with the dripping of calcium hydroxide emulsion,and it reached the maximum value of 12.96 at 105 min.Then it decreased continuously to 8.13 for the generation of HAP.The ratio of OH-consumption rate and the increase rate of defluoride quantity raised first and then lower.It increased to the maximum value of 4.98 at 180 min and was less than 1.00 after 235 min.The diameter of aggregated particle decreased with the increase of reaction time after 60 min.At 360 min,the d10,d_(50) and d_(90) of final product were 7.46,15.65 and 42.41μm,respectively.Compared to the control group,its d_(50) and d_(90) decreased by 56.83%and 52.21%,respectively.The HAP crystals were nano-level and they aggregated to form a micron particle.The fluoride in potable water could be removed quickly by the HAP prepared,and the fluoride removal con-formed to the proposed secondary dynamic model.