Chrome Removal From Wastewater Using Water Treatment Plant Sludge As An Adsorbent

Industries produces large amount of waste and the effluent of these wastes are oftenrnhazardous in polluting the environment and affecting human health. Tanneries are amongrnindustries which release large amount of waste which contains hazardous heavy metals suchrnas chromium. Hexavalent chromium in the environment is often harmful and it should berntreated before releasing to the environment. Chromium carcinogenicity to humans and otherrnliving organisms has promulgated extensive research on its treatment technologies withrnvarying levels of success.rnThe present study deals with removal of Cr(VI) by alum based water treatment sludge (Al-rnWTS) through batch and fixed bed column study. Response surface methodology (RSM) wasrnapplied in batch wise experiment for designing and analysis of experiment. Cr(VI)rnconcentration and pH increase, is shown to decrease chrome removal percent, whilernadsorbent dose and shaking time increase, is shown to increase chrome removal. Factorrninteraction terms: Cr(VI) concentration with pH shows that maximum chrome removalrn95.62.1% was obtained at Cr(VI) concentration of 2.4mg/l and pH 2.45, while interaction ofrnCr(VI) concentration and adsorbent dose shows, 97.06% chrome removal was obtained atrnchrome concentration of 3.3mg/L and adsorbent dose of 6.3g. Interaction of pH andrnadsorbent dose also shows that maximum chrome removal 92.2 was obtained at pH 2.44 andrnadsorbent dose of 6.17g. Theoretical Langmuir, Freundlich isotherms are subjected tornadsorption data to estimate adsorption capacity. The results gained from this study were wellrndescribed by the theoretical Langmuir and maximum adsorptive capacity of 33.33mg/g wasrnobtained.rnThe removal of Cr(VI) by Al-WTS was also investigated in a fixed bed column study.rnExperiments were conducted to study the effect of bed depth (10–30cm), flowrate (5–rn15mL/min) and initial concentration (10-30mg/L). The column data was fitted by BDST,rnThomas and Yoon-Nelson models. Adsorption capacity increases with increase in initial Cr(VI)rnconcentration and bed depth. Thomas model well fits the experiment and gives highrnadsorptive capacity of 14.8mg/L. Al-WTS was used for the Cr(VI) removal from tanneryrnwastewater in fixed bed column study and showed a high potential for the wastewaterrntreatment.rnKey words: Alum based water treatment sludge, batch adsorption, response surfacernmethodology, Cr(VI), fixed bed column

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