THE EFFECT OF SURFACE SITE DENSITY OF PARTICLES ON ADSORPTION BEHAVIOR OF DISPERSANT

Abstract

Adsorption behavior of polycarboxylate-based dispersant (PC) which has different chemical structure on calcium carbonate (CC) was investigated focusing on cationic site density on CC ([Ad site]). The authors measured amount of PC adsorption (Ad) under conditions that water solutions which have different concentration of Ca(NO₃)₂ was used as solvent of sample CC suspension in order to change [Ad site] intentionally. On other hand, authors calculated [Ad site] theoretically by considering reactions of complexes on CC under solvent conditions used in adsorption experiments. By comparing measured value of Ad and calculated value of [Ad site], authors examined effect of value of [Ad site] on adsorption behavior of PC on CC surface. As a result of analysis, under adsorption equilibrium, the number of cationic sites required for one of PC to adsorb on CC (N) was calculated to be constant value for identical PC, regardless of [Ad site]. From this result, it was suggested that adsorption density of PC under saturated adsorption shall be determined so that surface area occupied by a PC molecule is equal to product of N by [Ad site].化学構造の異なるポリカルボン酸系分散剤（以下、PC）の炭酸カルシウム（以下、CC）への吸着挙動をCC表面のカチオンサイト（＞CO₃Ca⁺サイトおよび＞CaOH₂⁺サイト）密度に着目して調べた。Ca（NO₃）₂の添加によりカチオンサイト密度を変えたCCの懸濁液を用いてPCの吸着量Adの変化を測定した。一方、CCの表面錯体反応を考慮することで、実験に用いた溶媒条件におけるカチオンサイト密度を理論的に計算した。Adの測定値とカチオンサイト密度の計算値との比較を行った結果、PCの飽和吸着時においてPC1分子が占有する面積内に存在するカチオンサイト数Nはカチオンサイト密度に因らず一定と推定された。またNとPCの分子構造には相関が見られ、NはPCの主鎖長に比例する結果となった。