随着pH 值的降低, 溶液中的CrO42- 不断地向Cr2O72-形式转化。在pH = 3 ～6 的酸性溶液中, 以Cr2O72-形式为主。另一方面，当pH 值减小时，树脂官能团上的胺基因吸附H+而带上较强的正电荷，有利于对Cr2O72-的吸附。当 pH<3 时，溶液中的Cr( Ⅵ)主要以HCrO4- 形态为主，从而使吸附量减小。
(专有名词可以用汉语直接代替,需要人工翻译,我先谢谢各位了)

The CrO42- in the solution continuously transform to Cr2O72- form along with the decreasing of the pH value.It is the Cr2O72- dominating when pH = 3 ～6 in the acid solution.On the other hand,the amic gene of colophony functional group absorb H+ when pH value is decreased.Thus carry around comparatively strong positive charge which will be helpful to absorb Cr2O72-.The Cr( Ⅵ) in the solution is mainly in HCrO4- form which consequently making the absorbing quantity decreased.