The adsorption of hexavalent chromium [Cr(VI)] onto bone char was optimised as a function of pH, initial Cr(VI) concentration, and bone char dosage using aqueous solution in batch tests. The initial Cr(VI) concentrations were varied between 5 and 800 mg/L to investigate equilibrium, kinetics, and the adsorption isotherms. About 100 % of Cr(VI) was removed at initial pH of 1.0 with initial Cr(VI) concentration of 10 mg/L, using 2 g of bone char after 2 hours. The maximum adsorption capacity of the bone char was 4.8 mg/g for an initial Cr(VI) concentration of 800 mg/L. The adsorption kinetics of Cr(VI) onto bone char followed a second order kinetic model. The adsorption isotherm followed the Langmuir model for Cr(VI) adsorption. In general, bone char demonstrated promising results as an effective adsorbent for removal of Cr(VI) from the aqueous solution. The results from this study could be useful in designing a filtration unit with bone char as the adsorbent in a full-scale water and wastewater treatment plant for the removal of Cr(VI) from contaminated water.

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Ammonium contamination in water is a major concern worldwide. This study focuses on the removal of ammonium from aqueous solution by batch adsorption experiments using biochar derived from a combination of various wood chips (spruce, pine, and fir). Adsorption characteristics of ammonium onto biochar were evaluated as a function of biochar dosages, initial concentrations of ammonium, contact time and pH. Results demonstrated that ammonium removal increased with the increase of biochar dosage. The percentage of ammonium removal reached a value of 80% at a biochar dosage of 100 g/L. Ammonium removal decreased by 15% with the increase of initial ammonium concentration by 50 mg/L. The optimum pH for ammonium removal was considered in the range from 6 to 8. Ammonium removal reached its stable value within 3 days. The maximum adsorption capacity of ammonium was 0.96 mg/g for 80 mg/L of initial ammonium concentration. The adsorption isotherm followed both the Langmuir and Freundich models for ammonium adsorption onto biochar. Fourier Transform Infrared (FTIR) spectroscopy results indicated the presence of amine, amide and nitrile functional groups on the surface of biochar which could contribute to the adsorption of ammonium onto biochar. Thus, biochar derived from various wood chips showed the potential to remove ammonium from aqueous solution.

Keywords: Oreochromis niloticusPhytoremediation Ceratophyllum demersum Lemna minorAquaculture Wastewater Pollution Two aquatic macrophytes, Ceratophyllum demersum and Lemna minor, were used in aquaculture wastewater treatment. Tilapia fish (Oreochromis niloticus) with total body weight of 50-60 g were placed in 60 L aquaria. Four treatment groups were included: control (no plant treatment, depended on artificial filtering for purification), Lemna minor (Lm), Ceratophyllum demersum (Cd), and mixed plants group (Lm+Cd). Each group had three replicates (5 fish/replicate). The experiment was conducted for 4 weeks. Physicochemical parameters of aquaculture wastewater including pH, total dissolved solids (TDS), conductivity, turbidity, dissolved oxygen (DO), chemical oxygen demand (COD), biochemical oxygen demand (BOD), total phosphorous (TPO 4 ), nitrate (NO 3 ), nitrite (NO 2 ), and ammonia were determined. The results reflected more effective removal of pollutants from fish aquaria by both plants than that by the artificial aeration/filtering. The effectiveness of pollution removal was higher in Cd group > Lm > Lm+Cd, compared to the control. This order of phytoremediation was confirmed by improvements in tilapia fish health status including liver function (AST, ALT, albumin), kidney function (creatinine, urea, uric acid), in addition to other nutritional and hematological parameters. It could be concluded that the phytoremediation using C. demersum is ecofriendly and effective in removing contaminants from Tilapia aquaculture wastewater and therefore, it is recommended to be applied in tilapia farms.

The characteristics of sorption of hexavalent chromium (Cr(VI)) onto bio-char derived from wood chips (spruce, pine, and fir) were evaluated as a function of pH, initial Cr(VI) concentration and bio-char dosage using synthetic wastewater in batch tests. The initial Cr(VI) concentrations were varied between 10 and 500 mg/L to investigate equilibrium, kinetics, and isotherms of the sorption process. About 100% of Cr(VI) was removed at pH 2 with initial Cr(VI) concentration of 10 mg/L using 4 g of bio-char after 5 hours of sorption reaction. The maximum sorption capacity of the bio-char was 1.717 mg/g for an initial Cr(VI) concentration of 500 mg/L after 5 hours. The sorption kinetics of total Cr onto bio-char followed the second-order kinetic model. The Langmuir isotherm model provided the best fit for total Cr sorption onto bio-char. The bio-char used is a co-product of a down draft gasifier that uses the derived syngas to produce electricity. Bio-char as a low cost adsorbent demonstrated promising results for removal of Cr(VI) from aqueous solution. The findings of this study would be useful in designing a filtration unit with bio-char in a full-scale water and wastewater treatment plant for the Cr(VI) removal from contaminated waters.