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Enhancement of sensitivity and rapidity for Hg(II) assay by FIA could be achieved by adding SDS in ascorbic acid. The method would be useful for routine analysis of Hg(II) in real samples.

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This work investigated the potential of generating biogas from mono-digestion of various substrates such as food and fruit waste (e.g., durian shell, dragon fruit peel and pineapple peel) and co-digestion in different combinations of a co-substrate as food waste as well as different types of fruit waste (durian shell, dragon fruit peel and pineapple peel). The mixture of food waste and fruit waste ratio varied as follows: 75:25, 50:50 and 25:75, which was based on weight. The batch experiments were carried out using 125 ml anaerobic digesters and were incubated for 50 days. For a mono-substrate, food waste produced the highest amount of methane gas (60.63 ± 1.02 ml/gvs) followed by durian shell (34.93 ± 1.30 ml/gvs), pineapple peel (31.70 ± 1.60 ml/gvs), and dragon fruit peel (30.12 ± 1.20 ml/gvs), respectively. The highest amount of methane gas came from food waste mixed with durian shell (FW75:D25), and it was on a higher level than food waste mixed with dragon fruit peel (FW75:DF25) and pineapple peel (FW75:P25). The highest methane gas production of co-digestion which was observed at the proportion of food waste and durian shell was 75:25 and produced higher content of methane gas than the highest methane gas production of mono-digestion (food waste) according to the high organic compound and optimum pH value in the system. The results showed that the co-digestion of durian shell and food waste improved methane production and reduced the startup time compared with their mono-digestion. On the other hand, pineapple peel was not suitable for co-digestion with food waste due to a decreasing pH value in the system.

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In this study, Salacca zalacca seed (SS) agricultural waste was employed as a material for the preparation of activated carbon. Salacca zalacca seed activated carbon (SSAC) was chemically activated using H3PO4 and used as an adsorbent for chromium (VI) adsorption. The effect of various experimental parameters such as activation temperature, impregnation ratio, and H3PO4 concentration (%) on adsorption capacity was determined using response surface methodology (RSM). The optimum condition prediction of these values from RSM alines well with experimental data; activation temperature (800 °C), impregnation ratio (3.50) and H3PO4 concentration (75 %). SSAC activated at the optimum condition were intensively characterized to understand the morphology, surface charge density, chemical composition and textural property by using SEM, pHpzc, FTIR, CHON analysis, and N2 adsorption- desorption. Maximum chromium (VI) adsorption was 7.94 mg/g. Langmuir adsorption model was effectively fi tted to the equilibrium adsorption information. Furthermore, the pseudo-second-order kinetic model also explains the experimental data well. Overall, the results suggested that RSM could optimize the preparation conditions of Salacca zalacca seed biochar, leading to enhancing the adsorption capacity of chromium (VI) using Salacca zalacca seed-activated carbon. Moreover, SSAC provides a excellent reusability for up to 6 cycles. This result ensures that SSAC has great potential as a low-cost, high-value agricultural waste adsorbent for chromium (VI) removal.