Synthesis of high-quality zeolite LTA from alum sludge generated in drinking water treatment plants

This study demonstrated the conversion of alum sludge produced at water treatment plants to high quality zeolite LTA. Thus, problems with landfilling costs and environmental contamination may be avoided. The methodology involved alkali fusion pre-treatment followed by hydrothermal synthesis improve quantity LTA made. Alum activation using facilitated formation high-quality (97 wt%) which was comparable commercial material (98 superior samples made without (81 wt%). Notably, derived contained greater amounts impurities such as iron, calcium, magnesium. Preferred conditions fusion-pre-treatment were: SiO2/Al2O3 = 2.5; Na2O/SiO2 3; H2O/Na2O 40; reaction time =5 h: temperature 80 °C. average particle size ranged from 0.7 (hydrothermal) 1.1 (fusion pre-treated) 3.0 (commercial) microns. Kinetic studies indicated that exchange calcium ions all reached equilibrium within 60 min. Equilibrium ion data revealed maximum loading 106.6, 83.9, 64.6 mg Ca2+/g for pre-treated, hydrothermally treated, LTA, respectively. However, on a “dry basis” cation capacity pre-treated similar.