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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.

A study was conducted to analyse the type and concentration of heavy metals found present in sediments samples in the Sungai Pinang river basin, Penang. River sediment samples were collected at both upstream and downstream along the main river channel of Sungai Pinang and its five tributaries including Sungai Air Terjun, Sungai Air Hitam, Sungai Air Putih, Sungai Dondang and Sungai Jelutong. A total of 19 sampling points were selected throughout the entire catchment area where nine points located at the main river of Sungai Pinang and the other 10 points located at the downstream and upstream of each tributaries. A total of 97 samples were obtained four times from January to February. Two types of analysis were applied to measure the heavy metal concentrations namely X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). For the XRF test, the selected compounds analysis containing heavy metals that was carried out were K2O, Na2O, CaO, MgO, MnO, Fe2O3, Al2O3, TiO2 and SiO2 while for the ICP-OES, specific heavy metals analysis were determined to test the presence of As, Ca, Cd, Co, Cr, Mg, Fe, Ni, Pb and Zn. The highest concentration of K2O, Fe2O3, Al2O3 and SiO2 at the main river were 2.80%, 3.39%, 18.52%, and 74.18% respectively. The highest concentration of Ca, Cr, Zn, Mg and Fe recorded at main river are 35.9576, 17.0469, 5.8392, 39.5626 and 199.914mg/kg respectively. SAH (DS) has the highest percentage of SiO2 with the value of 93.44% followed by Al2O3 with value of 6.75% at SAT(DS) and K2O at SD (US) with the value of 3.06%. The highest concentration of Fe, Ca, Mg and Pb are 56.4778 mg/kg at SAT (US), 34.8247 mg/kg at SJ (US), 3.3633mg/kg at SD (US) and 7.1662mg/kg at SAT (US). It can be concluded, the pollutants in the sediments of Sungai Pinang are contributed by the urban housing area, commercial and agricultural area.

The global demand for a wide variety of applications based on engineered nanoparticles (ENPs)has expanded the worldwide industrial scale production and inevitably released these materials into the environment. The increasing existence of NPs and its impact towards human health and the environment especially the aquatic system has sparked a great concern among both the scientific community and the public. It is therefore crucial to gain an in depth understanding of the properties the manufactured nanoparticles possess along with the various transformations they undergo that determine their behaviour and mobility. This review begins by addressing the fundamental physicochemical aspects of manufactured oxide nanoparticles with detailed attention given specifically to ZnO as a representative example in a separated section. The literature collected is summarized and focused on the essential point of view to evaluate their occurrence, fate and transport in the natural aquatic environment as a result of their interactions with other nanoparticles or natural colloids. Key methods and principles of nanoparticle characterization are also presented.

In this study, the zeta potential and z-average hydrodynamic diameter of zinc oxide (20 nm, 99.5% purity) were investigated as a function of pH and time. The nanoparticles readily formed aggregates and could not be disintegrated to its primary size eventhough ultrasonication was applied. In zinc oxide suspensions (25 mgL and 100 mg/L) the nanoparticles were examined for electrophoretic mobility and aggregation behaviour within the pH range of 3 to 11 and time duration of 60 minutes. In this study, the particle size and zeta potential were measured by dynamic light scattering technique. The application of nanoparticle tracking analysis was demonstrated as well to observe the aggregation and disaggregation of zinc oxide nanoparticles at various pH values. The NTA results obtained in this work were compared and validated by the DLS. The z-average hydrodynamic diameter of the particles was 389 d.nm with an average zeta potential value of +23 mV using the DLS compared to mean particle size of 365 d.nm by NTA. DLS analysis also identified the pH of the point of zero charge (pHPZC) and the isoelectric point (IEP) at pH 9.4 and pH 6.4 respectively. It was found that the zeta potential remained unaffected by the concentration of the suspension. However, results show that pH does have a pronounced effect on the stability of zeta potential, pH and particle size as a function of time in pH regions where dissolution (< pH 6.4 and 8.3 < pH < 10.5) and aggregation (pH 6.4 and 9.4) occurs. It is apparent that the pH of the suspension strongly influences the zeta potential of ZnO nanoparticles without external factors which will consequently govern their behaviour, agglomeration state and their interactions with each other and surfaces in the environment.

The surface charge and average size of ZnO was studied with a function of pH and time. The interactions between ZnO and Suwannee River humic acid (SRHA) were further investigated under a range of environmentally relevant conditions with the pHPZC as a point of reference. The anionic charge carried by aquatic humic substances plays a major part in the aggregation and disaggregation of metal oxide nanoparticles. At low concentrations of SRHA (PZC. With similar SRHA concentrations, at pH=pHPZC, SRHA was able to control the suspension behavior of the ZnO and promoted partial disaggregation in small volumes. This was more distinguishable as SRHA form a surface coating on the nanoparticles and enhances stability via electrostatic stabilization mechanism which induces the disaggregation behavior in the ZnO nanoparticles and hence, decreases the aggregate size.

The efficiency of using tapioca starch as a natural coagulant on semiconductor wastewater treatment was investigated. The silica content in the wastewater was pH dependent and it was found that the reduction of COD and turbidity occurred at pH between 12 and 14 with measurements below 100 mg/L and 100 NTU respectively. A three-level factorial design experiment in the Response Surface Methodology (RSM) was applied to determine the influence of retention time and dosage of the tapioca starch. The parameters studied were chemical oxygen demand (COD), turbidity and total suspended solids (TSS). The R2 for turbidity, COD and TSS were 0.92, 0.92 and 0.77 respectively. Results indicate that the dosage of the tapioca starch has a higher influence on COD and turbidity reduction. Tapioca starch as a natural coagulant has shown that the optimum turbidity reduction was 99% at a settling time of 30 minutes with dosage of 0.1 g/L. The COD reduction was achieved at 87% after 60 min of retention time and 0.1 g/L of dosage while higher coagulant dosages reduced the TSS concentration to 10.9 mg/L at retention time between 50 to 60 minutes.

A study was conducted to treat stabilized leachate by applying polyaluminium chloride (PAC) and tobacco leaf extract as a coagulant and coagulant aid. Experimental results indicated that the tobacco leaves were positively charged. The removal rate of the chemical oxygen demand, using 1500 mg/L PAC as a sole coagulant, was approximately 63% and increased to 91% when 1000 mg/L PAC was mixed with 1000 mg/L tobacco leaf. Additionally, 1500 mg/L PAC with 250 - 1000 mg/L tobacco leaf and 54% ammoniacal nitrogen was removed, compared with only 46% reduction using 1500 mg/L with only 46% reduction.

Les objectifs de ce travail de thèse concernent une meilleure compréhension des différents facteurs qui vont gouverner le comportement, le transport et les transformations de nanoparticules d'oxyde de Zinc, ZnO. L'oxyde de Zinc est très largement utilisé dans de nombreuses applications (cosmétiques, peintures, industrie automobile, etc). Nous nous sommes particulièrement focalisés sur l'effet du pH, de la force ionique, de la concentration en matière organique naturelle sur la modification de la charge de surface de nos nanoparticules et leur stabilité en solution à travers la mesure de tailles moyennes. Au final, les résultats présentés dans ce travail et à travers les nombreuses publications obtenues constituent des éléments de réponses importants quant au comportement des nanoparticules manufacturées du type oxyde de Zinc. Ils permettent de mettre en avant les paramètres importants à mesurer afin de pouvoir prédire le comportement de ces nanoparticules dans les systèmes aquatiques. Ces résultats montrent également que chaque nanoparticule manufacturée est unique.

The surface charge and average size of ZnO was studied with a function of pH and time based on the interactions between ZnO and alginate. The pHPZC ZnO was the point of reference. At low concentrations of alginate (