...
This semester the Arsenic Team was in its preparation phase. Since the GFAAS (Graphite Furnace Atomic Adsorption Spectrometer) is currently non-functional, the team concentrated the efforts in preparing the lab for upcoming experiments as well as creating standard testing procedures. I have supported the team by location and searching for necessary chemicals for the upcoming experiments. This semester, we require groundwater solution, which will be used as the basis for our sample solution. We also need diluted arsenic solution, nitric acid and permanganate. I also determined the sample tubes as main vessel for our experiment. This test tube has to fit in both the centrifuge and the carousel tray in the GFAAS. Professor Richardson gave us a variety of centrifugal tubes to test. These tubes come in two sizes both with sloped bottoms: 1,000 uL and 500 uL. Unfortunately, both sizes do not find the carousel slot. The large one is simply too wide, and the small one is too tall. The GFAAS also has its own 500 uL tube, which fits the carousel perfectly. However, it does not fit any centrifuge in available. Therefore, I came up with a hybrid solution, which is to place the small centrifugal tube inside the GFAAS tube when placing in the carousel. However, I will have to ensure that this odd configuration of tubes will not impede the machine in any ways. I also acquired a tube with filter basket, which we will use to emulate filtration.
Besides preparation, I also contributed to literature research. My main focus was on a paper by Katsoyiannic and Zouboulis on adsorptive filtration using coated polymeric materials, which is an emerging technology in water treatment process. The experiments in this study may be outside of our scope this semester. However, it provided us with possible alternatives to remove arsenic in groundwater, which we may study more intensively in the upcoming semesters.
As for the standard testing procedure experiment, I determined that there are four possible testing configurations. First, we can use regular centrifuge tube to mimic sedimentation. Second, the newly acquired tube with filter basket can be used to emulate filtration. Third, we can pre-treated the filter with coagulant to create adsorptive filtration. Last, we can add additional coagulant dose to the sample to mimic both normal flocculation and adsorptive filtration. Since we cannot use arsenic in our experiment, we used clay instead to observe the removal efficacy of these methods. We used a groundwater sample with turbidity of 5 NTU and 3 concentrations of PACl (2, 20 and 200 mg/L). The results are promising. Both coated and non-coated filtration methods were able to reduce the turbidity close to zero. However, there were some problems with sedimentation. I suspected that when we transferred sample from centrifuge tube to the spectrometer, we disturbed the sample and caused resuspension, thus tampering the results.