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This study focuses on the removal of nitrate ions from aqueous solutions using rice husk activated carbon (RHAC). The RHAC was subjected to characterization via Fourier transform infrared (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray florescence (XRF) to ascertain its functional groups, surface morphology, and oxide/elemental composition, respectively. Batch experiments were conducted to assess the impact of nitrate concentration, bed height, and number of packing layers on removal efficiency. FTIR spectra revealed favorable sorption-related functional groups within RHAC, while SEM analysis indicated the presence of effective sorption sites on its surface. EDS analysis of the rice husk adsorbent before adsorption (RHBS) demonstrated a significant composition of Si (42.20%), O (35.30%), and Ca (12.33%). The batch study unveiled a concentration--dependent decrease in nitrate removal efficiency, alongside the enhanced performance with increased bed height and number of packing layers. Kinetic data fitting favored the Yoon-Nelson and Adams-Bohart models. Overall, RHAC exhibited efficient nitrate ion removal, with column performance notably improved by utilizing multiple packing layers. These results will enhance our understanding of the mechanisms involved in removing nitrate ions and highlight the potential effectiveness of RHAC, especially when utilized with multiple packing arrangements in column setups. [ABSTRACT FROM AUTHOR]

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The work involves the treatment of abattoir wastewater (AWW) by coagulation technique using snail shell biomass as coagulant. The raw snail shell (RSS) sample and the processed snail shell coagulant (SSC) were analyzed for the determination of the predominant functional groups and surface morphology using Fourier Transform Infrared (FTIR) and Scanning Electron Microscopy (SEM) analytical techniques, respectively. Reduction in the turbidity of the effluent was used to assess the performance of the treatment process. The effects of the various factors affecting the efficiency of pollutants removal in the coagulation treatment process was studied in a one factor at a time (OFAT) process. A central composite design was used for designing the experiments, building models and determining the optimum conditions. FTIR spectroscopy revealed that the distinctive functional groups of RSS and SSC are amine, amide, hydrocarbons, and ethers. SEM analysis indicated that the processed SSC sample has a well-developed active site which is not present in the RSS sample. The coagulation-flocculation experiments showed that the removal efficiency of turbidity of the effluent increases with a decrease in solution pH and increase in coagulant dosage, settling time and temperature. A kinetic study revealed that the removal rate of total dissolved and suspended solids (TDSS) in the effluent showed conformity with the pseudo-second-order kinetic model. In the optimization study, an optimum turbidity removal of 94.39% was obtained at initial pH of 2, coagulant dosage of 1000 mg/l, settling time of 50 minutes and operating temperature of 50oC. A second order polynomial regression equation with R2 value of 0.9985 was obtained in the modeling process. The study has proved that snail shell biomass can successfully be used as coagulant in the coagulation treatment of abattoir wastewater. [ABSTRACT FROM AUTHOR]

Efficiency of electrocoagulation process for the removal of heavy metals (Pb2+, Mn2+, and Co2+) from simulated wastewater was investigated using iron electrode pair at five operational variables: pH (2–10), current density (0.076–0.189 A/cm2), inter‐electrode distance (3–7 cm), solution temperature (30–70°C), and charging time (5–20 min). Experiments were conducted as per central composite design (CCD), and the data was used for model building. Algorithmic optimization via hybrid response surface methodology (RSM)–genetic algorithm (GA)–particle swarm optimization (PSO) was studied where Pb2+, Mn2+, and Co2+ removal efficiency were monitored as responses from the finding equations of the CCD. Transition to the optimum removal (≥90%) of Pb2+, Mn2+, and Co2+ ions was achieved with current density of 0.19 A/cm2, solution temperature of 70°C, mean electrode distance of 3 cm and pH of 6.6 and charging time of 25 min for PSO relative to GA and RSM. Corresponding experiments conducted with the global optimal conditions show that the actual results (98.5, 90, 99%) were in reasonable agreement with the theoretical results of RSM (94.09, 90.82, 85.08%), GA (102.08, 87.91, 101.55%), and PSO (100.58, 90.91, 101.05%) for Pb2+, Mn2+, and Co2+, respectively. The mean error indices of 6.43, 2.83, and 1.73% for RSM, GA, and PSO, respectively, indicate that PSO guarantees best convergences to true optimal. [ABSTRACT FROM AUTHOR]