Functionalization and Formation of Drinking Water Filter Rod from Lignite with Zeolite, Bentonite, and Local Clay

A drinking water filter rod was functionalized and formed from a starting mixture of lignite, zeolite, bentonite, and clay. The formation of the filter was studied focusing on the effects of zeolite dosage and sintering temperature in a reducing atmosphere. Borax was also added to the starting mixtures for melting point reduction. The sintered filters were characterized by XRD, FTIR, and SEM-EDS. The percent drying shrinkage, percent firing shrinkage, percent total shrinkage, percent mass yield, percent fixed carbon, and hardness of filters were measured. The results showed that the firing shrinkage, the total shrinkage and hardness increased with increasing sintering temperature. The hardness of sintered filters is higher than the limit of the Thai Industrial Standards Institute. On the other hand, mass yield and fixed carbon decreased with increasing sintering temperature. The starting materials mixture of 45wt% lignite, 30wt% zeolite, 10wt% bentonite, 10wt% local clay, and 5wt% borax was used with sintering temperatures ranging from 400 ºCto 600ºC. The functional surface groups of the sintered filter exhibited a high content of aluminosilicates and carbon, which were derived from all starting materials. The macropores of sintered filter had dimensions of the channels between particles in the range of 0.2–2 μm.