Use of enameling wastewater in the wet milling process for ‘monoporosa’ tile composition

Abstract

Water is becoming scarce for ceramic processing, even in certain regions of Brazil. In the wet milling process, the ceramic slips are formed by 30 wt% water to achieve the adequate density and viscosity for an efficient milling. Wastewater from other ceramic processes, as enameling, could be used for milling. The aim of this work was the study of the milling process of a ceramic tile composition using wastewater without treatment in place of clean water. The raw materials forming the ‘monoporosa’ composition and the wastewater were characterized (XRF, particle size) as well as the monoporosa composition (STD) (XRD, residue at #325 ASTM sieve, flow time viscosity, density). The milling parameters were mill rotation (15 or 19 rpm), mill loading capacity (70 or 100%) and type of water (wastewater or clean water) used as the factors (and levels) in a full factorial design, totaling 8 experiments (levelfactor = 2³). The tests were carried out in a mill of 148 L capacity, with a load of 87 kg of raw materials and addition of 34 L of wastewater (1.05 g/L) or clean water (1.0 g/L density). The density, viscosity, and residue at the 4, 6, 8 and 10th hour of milling were determined. As a result, the use of wastewater increases the density of the liquid medium and thus increases the milling residue, as evidenced in the 10th milling hour. At the end of the work, it was possible to reduce the total milling time in a 12,000 L industrial mill by 2 h (25%), without changing the characteristics of the slip, even using wastewater as liquid medium.

Keywords

• Ceramic tile industry
• Reuse of wastewater from enameling
• Efficiency of wet milling
• Design of experiments