Much of Nepal lacks access to clean drinking water, and many water sources are contaminated with arsenic at concentrations above both World Health Organization and local Nepalese guidelines. While many water treatment technologies exist, it is necessary to identify those that are easily implementable in developing areas. One simple treatment that has gained popularity is biochar—a porous, carbon-based substance produced through pyrolysis of biomass in an oxygen-free environment. Arizona State University’s Engineering Projects in Community Service (EPICS) has partnered with communities in Nepal in an attempt to increase biochar production in the area, as it has several valuable applications including water treatment. Biochar’s arsenic adsorption capability will be investigated in this project with the goal of using the biochar that Nepalese communities produce to remove water contaminants. It has been found in scientific literature that biochar is effective in removing heavy metal contaminants from water with the addition of iron through surface activation. Thus, the specific goal of this research was to compare the arsenic adsorption disparity between raw biochar and iron-impregnated biochar. It was hypothesized that after numerous bed volumes pass through a water treatment column, iron from the source water will accumulate on the surface of raw biochar, mimicking the intentionally iron-impregnated biochar and further increasing contaminant uptake. It is thus an additional goal of this project to compare biochar loaded with iron through an iron-spiked water column and biochar impregnated with iron through surface oxidation. For this investigation, the biochar was crushed and sieved to a size between 90 and 100 micrometers. Two samples were prepared: raw biochar and oxidized biochar. The oxidized biochar was impregnated with iron through surface oxidation with potassium permanganate and iron loading. Then, X-ray fluorescence was used to compare the composition of the oxidized biochar with its raw counterpart, indicating approximately 0.5% iron in the raw and 1% iron in the oxidized biochar. The biochar samples were then added to batches of arsenic-spiked water at iron to arsenic concentration ratios of 20 mg/L:1 mg/L and 50 mg/L:1 mg/L to determine adsorption efficiency. Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicated an 86% removal of arsenic using a 50:1 ratio of iron to arsenic (1.25 g biochar required in 40 mL solution), and 75% removal with a 20:1 ratio (0.5 g biochar required in 40 mL solution). Additional samples were then inserted into a column process apparatus for further adsorption analysis. Again, ICP-MS analysis was performed and the results showed that while both raw and treated biochars were capable of adsorbing arsenic, they were exhausted after less than 70 bed volumes (234 mL), with raw biochar lasting 60 bed volumes (201 mL) and oxidized about 70 bed volumes (234 mL). Further research should be conducted to investigate more affordable and less laboratory-intensive processes to prepare biochar for water treatment.

Using DFT calculations and GAMESS computational software, porphine and its derivatives were analyzed for unique sites to accept the adsorbates As(III), As(V) and P(V) in order to compare resulting adsorption energies and determine if any of these molecules prefer arsenic oxyanions over phosphate. Pure porphine preferred As(III) over P(V) with a resulting adsorption energy of -0.7974 eV. Of the functionalized porphyrins tested, carboxyl porphyrin preferred As(V) over P(V) with a total adsorption energy of -0.7345 eV. Ethyl, methyl, chlorine and amino porphyrin all preferred As(III), with energies of -0.7934, -0.8239, -0.7602, and -0.8508 eV, respectively. Of the metalated porphyrins tested, copper and vanadium porphyrin preferred As(V) over P(V) with adsorption energies of -0.7645 and -2.0915 eV. Chromium, iron and magnesium porphyrin all preferred As(III) over P(V) with energies of -0.5993, -1.4539, and - 1.0790 eV, respectively.

Esters are important solvents in multiple industries including adhesives, food, and pharmaceuticals. Although esters are biodegradable solvents, the conventional process of producing them is not eco-friendly because they are largely derived from petrochemicals. This has led scientists to consider implementing biological routes in their production process by incorporating heterologous or improving inherent esterification pathways. However, due to inequality in the biosynthesis of esters and their precursors (organic acid and alcohol), a significant amount of precursors are left unconverted, thereby lowering overall esterification efficiency. Therefore, the primary goal of the current research is to improve the ester titers by incorporating one more step of in vitro esterification with the culture broth, thereby esterifying the unconverted precursors using high efficiency commercial enzymes in the presence of compatible organic solvent. In principle, the medium containing the precursors will be treated with the enzyme in presence of organic solvent, where the precursors will be distributed in both the phases, aqueous and organic, based on their polarity, and the enzymatic esterification will happen at the interface. Hence, as a first step, efforts were made to optimize the reaction conditions, beginning with choosing the most efficient organic solvent and corresponding enzyme candidate. Our results showed that, for production of ethyl acetate through this reactive extraction approach, Novozyme435 exhibited significant esterification with chloroform, with almost 85% conversion efficiency. Further optimizations with phase ratios, pH and incubation time showed that the pH 6.0 (3.1 g/L) was the most optimum where ethyl acetate titer was found to improve 10 times than that at pH 7.0 (0.164 g/L) with the phase ratio of 1:1. The kinetic studies further added that the incubation at 37oC gives the maximum ethyl acetate production within 8h. After initial optimization studies, cell broth from E. coli cells transformed to overproduce an esterase was also tested with the reactive extraction method. It was found that there was a ~7.5X decrease in ethyl acetate production in the cell media versus synthetic samples with the same concentration of reactants. Such a large decrease indicates that enzymatic promiscuity or inhibition currently prevent the cell samples from reaching the same conversion as synthetic studies. To characterize the maximum reaction rate (Vmax) and affinity constants of the substrates to Novozym 435, further kinetic studies were performed with one minute of reaction. The mathematical model employed assumes that enzyme kinetics rather than diffusion was the rate limiting step, that the concentrations of reactants at the interface are equivalent to the initial concentration of reactants, and that neither substrate is an inhibitor. Vmax was found to be 18.5 Mmol min-1g-1 (of catalyst used), and the affinity constants were 0.957 M and 0.00557 M for acetic acid and ethanol respectively. Vmax was similar to literature values with Novozym 435, and the affinity constants indicate a much higher binding efficiency of ethanol in comparison to acetic acid, indicating that a cocktail of esters are likely produced from Novozym 435 in cell broth. Overall, moving away from fossil-fuel dependence is necessary to promote sustainable industry standards, and microbial cell factories combined with reactive extraction, if optimized for industrial applications, can replace harmful environmental procedures. By optimizing the reactive extraction process for ester production, biorefineries could become more competitive and economically feasible for numerous applications.

Utilizing DFT calculations, various substitutions on the AlPO-5 zeolite were screened for adsorption of common air molecules. Furthermore, free energy analyses using the Helmholtz free energy equation were performed to determine candidates for selective adsorption of one specific air molecule, and their operating temperature range. Through this study, it was found that Cerium- (92-542 K), Germanium- (69-370 K), Chromium- (35-293 K), and Praseodymium- (0-420 K) substituted AlPO-5 selectively adsorbs to O2 molecules for the given temperature ranges. In addition, Palladium-substituted AlPO-5 selectively adsorbs to CO within 430-755 K.