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  • Author: Fatehah Mohd Omar x
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Abstract

The recent climate condition and pollution problem related to surface water have led to water scarcity in Malaysia. Huge amount of groundwater has been identified as viable source for drinking water. This paper was aimed to investigate groundwater’s quality at specific location and metakaolin’s potential in the groundwater treatment in the removal of manganese. Groundwater purging was determined to be sufficient at 120 minutes where all three parameters (pH, dissolved oxygen and conductivity) were stabilized. The groundwater studied is classified as both anoxic and reductive due the low dissolved oxygen value. It also can be categorized as brackish due to high value of conductivity and total dissolved solid. Manganese content in groundwater was determined as higher than of that permissible limit for raw water and drinking water which makes it unsuitable for them not suitable for consumption and cleaning purpose. Average manganese concentration in samples was 444.0 ppb where the concentrations of manganese ranged from 229.4 ppb to 760.3 ppb. Manganese developed is not that a strong positive correlation against iron concentration, total dissolved solids and conductivity; whereas has a moderate negative correlation against dissolved oxygen. The capability adsorption of manganese by metakaolin was assessed via batch method which indicated optimum dosage and contact time was 14g that removed average 30.2% and contact time optimum at 120 minutes which removed 33.2% manganese from the sample.

Abstract

Chemical mechanical polishing (CMP) wastewater generated from semiconductor manufacturing industries is known to contain residual organic and inorganic contaminants, i.e. photoresists, acids, including silicon dioxide (SiO2), nanoparticles (NPs) and others. Nanoscale colloids in CMP wastewater have strong inclination to remain in the suspension, leading to high turbidity and chemical oxygen demand (COD). Although various types of pre-treatment have been implemented, these nanoparticles remain diffused in small clusters that pass through the treatment system. Therefore, it is crucial to select suitable pH and coagulant type in the coagulation treatment process. In this research zeta potential and dynamic light scattering measurements are applied as preliminary step aimed at determining optimum pH and coagulant dosage range based on the observation of inter particle-particle behavior in a CMP suspension. The first phase of the conducted study is to analyze nanoscale colloids in the CMP suspension in terms of zeta potential and z-average particle size as a function of pH within a range of 2 to 12. Two types of coagulants were investigated - polyaluminum chloride (PACl) and ferrous sulfate heptahydrate (FeSO4·7H2O). Similar pH analysis was conducted for the coagulants with the same pH range separately. The second phase of the study involved evaluating the interaction between nanoscale colloids and coagulants in the suspension. The dynamics of zeta potential and corresponding particle size were observed as a function of coagulant concentration. Results indicated that CMP wastewater is negatively charged, with average zeta potential of -59.8 mV and 149 d.nm at pH value of 8.7. The interaction between CMP wastewater and PACl showed that positively charged PACl rapidly adsorbed colloids in the wastewater, reducing the negative surface charge of nanoscale clusters. The interaction between CMP wastewater and FeSO4·7H2O showed that larger dosage is required to aggregate nanoscale clusters, due to its low positive value to counter negative charges of CMP wastewater.