A biosorbent's low chemical stability against oxidative attack and its poor regenerability are problems that limit the applicability of biosorption in addressing the problem of recovering chromate in industrial wastewater. To provide a sufficient premise for such an argument, original equilibrium and kinetic data on the biosorption of chromate by the biomass of the brown seaweed Sargassum siliquosum are presented and benchmarked with other related reports. It is established that the optimal condition for chromate biosorption is around pH 2. It is shown that electrochemical reduction of some of the chromate in the solution occurs in parallel with biosorption. Aside from the solution pH, the other factors shown to influence the equilibrium and the kinetics of both biosorption and reduction are the amount of biomass and the total chromate concentration. The chromate bound by the seaweed is found to be difficult to desorb using H2SO4 without first reducing the hexavalent chromate into a trivalent chromium. These findings are shown to be common among other reported studies using different biosorbents. In conclusion, it is argued that biosorption is not a highly viable option for the recovery of chromate in industrial wastewaters.

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A new rotating biological contactor-packed media technology (RBC-PMT) is locally innovated using light polyethylene Amazon screen material as disc media. A single-stage co-current fed of this type, which is connected with a series of equalization tanks as an integrated wastewater treatment system (IWWTS), showed good carbonnitrogen-phosphorus (C-N-P) removal and unveiled biofilm growth characteristics noteworthy for treating pollutants in wastewater.The equalization tanks approached facultative anaerobic conditions while the RBC-PMT exhibited a completely aerated system, both with a slightly alkaline pH, whose temperatures are ranging from 21 to 24• C, and both performed as biological nutrient removal systems. The combined nutrient removal efficiency at high organic loading rate (HOLR) and low organic loading rate (LOLR) showed fair chemical oxygen demand (COD) removal at 65.68 and 67.89%, respectively. Nitrate-nitrogen removal demonstrated good removal at 79.17% at HOLR and 83.43% at LOLR. There was excellent phosphate-phosphorus removal determined at 91.64 and 94.35% at high and low OLRs, respectively. This indicates that increasing the organic loading rate decreases the C-N-P removal in the IWWTS.Biofilm growth was characterized by the selection and survival of microorganisms present under aerobic environmental conditions in the RBC-PMT system and their respective metabolism in removing C-N-P substrates. Yeasts, coliform bacteria particularly E. coli, Cyanobacteria, and benthic diatoms were dominant microorganisms found upon oil-immersion microscopy. Protozoans and algae including Chlorococcum, Chlorella, Diatoma, Tribonema, Oscillatoria, Euglena, and other motile rotifiers were also dominantly found in the biofilm samples. Biofilm growth is observed and its average thickness was measured to be 7.71 µm at HOLR and 2.81 µm at LOLR. Thicker biofilm at HOLR has caused the reduced rate of diffusion of the microorganisms and their metabolic products as manifested by the low C-N-P removal during HOLR. 

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Production of diglycerides (DG) plays an important role in food, pharmaceutical, and cosmetic industries. In this study, optimal conditions for DG synthesis via noncatalyzed esterification of oleic acid with glycerol were determined. The temperatures (150°C, 175°C, and 200°C), oleic acid to glycerol molar ratios (1:1, 2:1, 3:1, and 4:1), and initial water content were varied to determine DG selectivity and % conversion over an 8‐hr period in a nitrogen‐purged system. The results exhibited a similar trend to catalyzed studies wherein an increase in temperature and molar ratio leaned towards the production of triglycerides (TG). It was also noted that tested initial water contents had an insignificant effect on reaction rates and product selectivity. Addition of molecular sieves for removal of water also resulted in negligible effects within this temperature range. DG production is optimum at 175°C and 2:1 molar ratio at 4 hr resulting in a product containing 42.6 ± 0.92 wt.% DG and a process selectivity of 1.11 ± 0.06 g DG/g (monoglycerides + TG). Purification by silica gel column chromatography of the product with the highest selectivity resulted in an enriched mixture with a yield of 58.25% and purity of 86.95 wt.% DG. Compared with catalyzed reactions, this system would require less downstream processing as removal of catalysts is not required and saponification does not occur. Although this procedure involves higher reaction temperature compared with enzyme‐catalyzed reactions, the time required to obtain high conversion is much shorter.