Abstract:

The nanoscale humic acid-urea complexes of 70—90 nm were prepared using nanoscale humic acid and urea as raw materials through complex reaction in order to determine their production process conditions and physical and chemical properties. The optimal process conditions of preparation nanoscale humic acid-urea complexes using response surface methodology was as follows: reaction temperature 47.6℃, reaction time 1.80 h, sodium dodecyl sulfate (as activator) concentration 50.0% (mass), solid-liquid mole ratio 9:1, concentration of complexing agent 0.14 mol·L^-1 and urea dosage 200 mg. Three separate experiments were carried out in the above conditions with product yield of 90.6%±0.9%, which was agreed with the predicted yield of 91.2% by the model. The quadratic polynomial equation model of response and factor was established. The crystal form, component, morphology and specific surface area were characterized respectively by XRD, FTIR, TG, SEM, BET and so on. The results showed that the complex had perfect crystal form, high purity, uniform granularity and good dispersibility with particle size of 70—90 nm, specific surface area 189.85 m²·g^-1, mean pore size 10.2 nm and pore volume 0.86 cm³·g^-1, and also higher heat stability.

Key words: nanoscale humic acid-urea complexes, response surface methodology, preparation, optimization, model

摘要：

为确定纳米腐殖酸-尿素配合物形成工艺参数和物化性质,以纳米腐殖酸和尿素为原料,通过络合反应制备了70~90 nm腐殖酸-尿素配合物,用响应面法优化制备纳米腐殖酸-尿素配合物最佳工艺参数为:反应温度47.6℃,反应时间1.81 h,活化剂十二烷基硫酸钠浓度50.0%(质量),固液体摩尔比9:1,络合剂浓度0.14 mol·L^-1,尿素用量200 mg,产率预测值91.2%, 此条件下进行3组独立实验,产物产率为90.6%±0.9%,与模型的预测值吻合。拟合出响应值和影响因子间的二次关联方程模型。并用X射线衍射仪(XRD)、红外光谱仪(FTIR)、热重分析仪(TG)、扫描电镜(SEM)与吸附-脱附比表面仪(BET)等物理手段对产物晶型、组分、形貌大小及比表面积等进行表征。结果表明:配合物晶型完整纯度高,粒度大小均匀且分散性良好,粒径为70~90 nm,比表面积189.85 m²·g^-1,平均孔径10.2 nm,孔容0.86 cm³·g^-1,具有较高热稳定性。

关键词: 纳米腐殖酸-尿素配合物, 响应面法, 制备, 优化, 模型