Effect of precipitation and aging on porous structure of aluminium hydroxide. II. Changes in pore size distributions

Abstract

Differences in porous structure of the dried aluminium hydroxide (containing sulphate ions) caused by changes in temperature and pH of precipitation, the time of aging and by additions of surfactants are documented and discussed. The aluminium hydroxide precipitated at low temperatures (30 – 50°C) and pH values (7 – 8) has bi-disperse porous structure with maxima in the region of large and medium pores. The increase of temperature and pH of precipitation limits or completely suppresses medium pores and increases large and small pores. Characteristic trend was the disappearance of medium pores which led to monodispersity in the region of large and small pores. The addition of surfactants suppressed the effect of short-time aging on pore size distributions. At moderate temperatures the effect of surfactants manifested itself in the broad pore size distributions and in the increase of the volume of large and medium pores. Qualitative and quantitative differences in porous structure caused by the action of surfactants were suppressed on increasing temperature and pH of precipitation.