Electrocoagulation Combined with Synthetic Zeolite—Does the Size of Zeolite Particles Matter?

Abstract

Although electrocoagulation combined with zeolite (ECZ) shows higher efficiency in wastewater treatment, the actual contribution of zeolite particle size has not been fully explored. In this work, the influence of particle size of synthetic zeolite SZ (<90, 90–160, and 160–600 μm) on ECZ treatment of compost leachate with very high organic load is investigated together with different electrode materials (Fe, Al, and Zn), current densities (0.003, 0.009 and 0.018 A/cm2), and contact times (10, 20 and 30 min). The results positively highlight that the largest particle size should be used in ECZ, as it leads to a lower increase in pH and temperature, a higher decrease of chemical oxygen demand (COD) and turbidity, and a lower electrode consumption, while causing more damage to the electrode surface. The estimated energy costs ranged from 3.960 kW/m3–1313.657 kW/m3. The Taguchi L9 orthogonal configuration showed the highest COD and turbidity decrease under the conditions of 160–600 µm zeolite particles. The powder X-ray diffractometer (PXRD) analysis shows that interplanar spacing decreases when smaller and medium SZ particle sizes are used, while this effect was not observed with larger zeolite particle size. SEM-EDS shows that oxygen, silicon, and aluminium are the predominant elements in electrogenerated sludge coupled with zeolite.

Učinkovitost obrade elektrokoagulacije kombinirane s različitim veličinama čestica prirodnog zeolita

“…Compared to previous results carried out with synthetic zeolite, 23 the largest particle size of both synthetic and natural zeolite during the ECZ process led to a smaller increase in pH (pH in range 4.24-4.30 with the largest particle size, see Table 2). However, better results in decreasing COD and turbidity were obtained with a smaller particle size of natural zeolite < 90 µm (COD decrease in the range 17.94-37.40 %; turbidity decrease in the range 91.51-98.46 %, see Table 2), while with synthetic zeolite, better removal was obtained with the largest zeolite particle size of 160-600 µm.…”

“…conductivity = 3.54 mS cm −1 , turbidity = 397 NTU, COD = 10427.6 mg O 2 l −1 , and total solids (TS) = 10.33 g l −1 . 23 All parameters were determined according to standard methods for the analysis of water and wastewater. 24 The initial solution temperature was 23.7 °C.…”

“…This combination and the values of the factors have already been studied with synthetic zeolite, whereas natural zeolite was used in this study. 23 For the experimental design shown in Table 1, a full factorial experimental design with four factors and three levels would require a total of 81 experiments.…”

“…7,22 Previous studies have shown that a larger particle size of synthetic zeolite should be utilised in ECZ, resulting in a smaller rise in pH and temperature, a more significant decrease in solution turbidity and COD, and reduced electrode consumption; however, with more damage to the electrode surface. 23 The aim of this study was to investigate whether natural zeolite of three different particle sizes has the same effect on the ECZ process as synthetic zeolite. Taguchi ECZ optimization was conducted under the same conditions as for synthetic zeolite, 23 using three different electrode materials (carbon steel, aluminium alloy, and sacrificial zinc anode), three particle sizes of natural zeolite ranging up to 600 µm, a current density in the range 0.003-0.018 A cm −2 , and contact time in the range 10-30 min.…”

“…23 The aim of this study was to investigate whether natural zeolite of three different particle sizes has the same effect on the ECZ process as synthetic zeolite. Taguchi ECZ optimization was conducted under the same conditions as for synthetic zeolite, 23 using three different electrode materials (carbon steel, aluminium alloy, and sacrificial zinc anode), three particle sizes of natural zeolite ranging up to 600 µm, a current density in the range 0.003-0.018 A cm −2 , and contact time in the range 10-30 min. The treatment efficiency of compost leachate with a very high organic load was evaluated by measuring COD and turbidity decrease, electrode consumption, and analysing the change in electrode surface using an optical microscope.…”