In this study, Mangifera Indica (mango) seed kernel powder was used as an adsorbent for chromium(VI) removal. The interactive effects between the process variables such as pH, temperature, adsorbent concentration, chromium concentration, and stirring speed (RPM) on chromium(VI) removal have been studied. In order to optimize the process, the experiments were designed using central composite design under response surface methodology by MINITAB 16.0 software. Based on the study, the optimum conditions for maximum removal of chromium(VI) from synthetic solution were obtained as: pH 1, temperature 27.5 degrees C, adsorbent concentration 3.5g/L, chromium concentration 100ppm, and RPM 75. The statistical analysis of the data shows that experiments are statistically significant with a regression coefficient (R-2) value of 0.95.

In this study, the removal of hexavalent chromium from aqueous solution using ragi husk, an agricultural waste, has been reported. Response surface methodology was applied to statistically optimize the process variables such as pH (2–4), adsorbent dosage (2–5 g/L), initial chromium concentration (50–150 mg/L), rotating speed (50–100 rpm), and temperature (25–30°C) using the main effect plot and central composite design. A maximum removal of 68.64% of Cr(VI) was achieved under the optimum conditions of pH 2, adsorbent dose 2 g/L, initial chromium concentration 150 mg/L, rotating speed 100 rpm, and temperature 30°C. The statistical analysis of the data shows that the experiments are statistically significant with a regression coefficient ( R 2 ) value of 0.9445. The surface morphology of the adsorbent was elucidated using scanning electron microscopy, and the functional groups present in the adsorbent that aids in the removal of Cr(VI) were identified using Fourier transform infrared spectroscopy. The experimental results revealed that ragi husk can be used as a potential adsorbent for the removal of hexavalent chromium from aqueous solution. © 2014 American Institute of Chemical Engineers Environ Prog, 34: 139–145, 2015

Microalgae have the potential to utilize the nutrients in the wastewater for its growth and serve as a primary feedstock for the production of value added products. A feasibility study has been conducted to determine the capability of the microalgae (Chlorella sp) to grow in sewage without sterilization in a laboratory scale batch process under the continuous illumination of light. In the present investigation, the algal growth and nutrients removal in the sewage has been studied and the experimental results revealed the growth period of microalgae as 9 days. The nutrients present in the sewage after algal growth was compared with the nutrients in the initial stage. The percentage removal of nutrients after the end of batch process is Phosphate-90.7%, Total solids -86%, Nitrates-Nitrogen-60%, Ammonia-Nitrogen-58.8%, Total dissolved solids -90%, and Total suspended solids -50%, respectively.