N-Dodecylethylenediamine (ND), which could be obtained by introducing secondary amino group into dodecylamine (DDA), has been testified to exhibit better flotation recovery for quartz than dodecylamine. In order to clarify the adsorption mechanism of ND on quartz surface, especially the effect of additional function group (-NH-) in the adsorption process, the states of absorbed ND on quartz surface as a function of pH were discussed by molecular dynamics simulation method. The results indicated that both of the primary amino group (-NH2) and secondary amino group (-NH-) participated in the adsorption process. Moreover, the participation of secondary amino group adsorption on quartz surface increased the collectability of ND for quartz by adding extra active site. Flotation results indicated that neutral and weak base environment was favorable for quartz flotation. Computational results revealed that the protonated group with positive charge could adsorbed on quartz surface via electrostatic attraction, and hydrogen bond formed between hydrogen of protonated polar group and oxygen of quartz surface. (C) 2019 Elsevier B.V. All rights reserved.