REMOVAL OF CHROMIUM AND PHENOL FROM SINGLE AND BINARY SIMULATED SYNTHETIC TANNERY WASTE WATER

Abstract

With the increase in industrialization worldwide, industries such as electroplating, leather tanning, textile, paints and pigments discharge toxic effluent, which contains Cr(VI) and organic matter like phenol (Gupta et al. 2015; Song et al. 2009). Both chromium and phenol are used in tanneries in the tanning process for the manufacturing of leather (Munz et al. 2009; Srivastava et al. 2007). Simultaneous removal of Cr(VI) and phenol is a matter of concern for the industries such as tanneries, photographic-film production, preservation of wood, manufacturing of car, petroleum refining and agricultural production because Cr(VI) and organic pollutants like Phenol, naphthalene are discharged simultaneously from the waste effluent of these industries. Two stable oxidation states of chromium such as trivalent [Cr(III)] & hexavalent [Cr(VI)] are found in the environment. Cr(VI) is in the form of chromate (CrO42-) or dichromate (Cr2O72-) ions while Cr(III) is in the form of oxides, hydroxides or sulphates and less mobile than Cr(VI) but it can be oxidized to Cr(VI) (Thinh et al. 2013). Cr(III) is hazardous to the plants and living beings only at higher concentration and less toxic to animals or living beings while Cr(VI) is mutagenic and carcinogenic to the living organism. Cr(VI) enters into the human body causes epigastric pain, nausea, vomiting, severe diarrhea, corrosion of the skin, respiratory tract and lung carcinoma. Hence, removal of Cr(VI) from industrial effluents becomes necessary before its discharge to main water sources. Among the various harmful and toxic organic compounds like dyes, pesticides and fluorine, phenol is most toxic to the environment. Phenol is a weak biodegradable and toxic aromatic compound and consumption of phenol causes various diseases such as gastrointestinal disorder, lung damage, liver disease, kidney disease, heart attack and finally death of living beings (Chaudhary et al. 2014). WHO (world health organization) sets the maximum permissible limit for Cr(VI) and phenol as 0.05 and 1 mg/L, respectively (Vlyssides et al. 1997; Chaudhary et al. 2014). Various methods are developed for the removal of toxic metals and organic compounds from waste effluent such as oxidation-reduction (Dittert et al. 2014), electro coagulation (Hamdan et al. 2014), reverse osmosis (Lin et al. 2014), evaporation (Sun et al. 2011), ion exchange (Cavaco et al. 2015), photocatalytic oxidation (Gupta et al. 2012; Saleh et al. 2012), elecrokinetic remediation (Sawadaa et al. 2004) etc. But these methods are associated with various disadvantages such as high energy and chemical requirements, low efficiency and generate large amount of sludge (Ahmaruzzaman et al. 2011). Therefore there is a need for the development of method which overcomes theses problems. Biological treatment of toxic metal and organic compounds from wastewater is a new emerging technology, does not produced ii secondary waste and cost effective but yet to be established and commercialized (Dash et al. 2008). Biosorption of toxic pollutant using agricultural waste material is a low cost technology, high selectivity and efficiency of removal of pollutant used for the removal of heavy metal and organic compounds from industrial wastewater (Uluozlu et al. 2008). Various methods are used for the analysis of Cr(VI) and phenol such as on-line flame atomic absorption spectrophotometry, UV spectrometric method, inductively coupled plasma mass spectrometry (ICP-MS) (Saracoglu et al. 2002; Sadaf et al. 2014). In the present study, single component and binary synthetic simulated wastewater was prepared in the laboratory. The residual concentration of Cr(VI) and phenol of these water samples were analyzed through the UV spectrophotometer (HACH DR 5000). The 1, 5 diphenyl carbazide method at a wavelength (λ) of 540 nm was used for analysis of Cr(VI) and 4 amino antipyrene method at wavelength of 510 nm was used for the analysis of phenol. The work has been divided into four sections, namely (i) application of adsorption and simultaneous adsorption and bioaccumulation of Cr(VI) and simultaneous adsorption and biodegradation of phenol from single and binary solution, (ii) application of continuous reactor system for simultaneous removal of Cr(VI) and phenol (iii) application of phytoremediation using water hyacinth. i) Application of adsorptive system for single and multicomponent system: Agricultural waste products such as tea waste (TW), Rice husk (RH), Bagasse (BG), Bagasse fly ash (BFA), Distillery sludge (DS), Neem leaves (NL), Fe treated tea waste (Fe TW) and Fe treated rice husk (Fe RH) and granular activated carbon (GAC) were selected as adsorbents for adsorption studies for the removal of Cr(VI) and phenol from single component synthetic simulated solution. GAC is used in the present study as control since it has been widely used in the removal of number of heavy metals from the effluent of industrial wastewater, reported in literature. The best adsorbent selected from single component solution for the removal of Cr(VI) and phenol were used for the simultaneous removal of Cr(VI) and phenol from binary solution. For characterization proximate, ultimate, SEM-EDX, FTIR and BET surface area, were performed. The surface modifications of the selected adsorbents by iron impregnation were performed in order to increase the capacity of the adsorbents for the removal of Cr(VI) and phenol from single component and binary solution. Optimization of process parameters viz. pH, contact-time, temperature, adsorbent dosage and initial concentration were performed. Tea waste, Rice husk, Fe treated tea waste, Fe treated rice husk and GAC were proved to be best adsorbent out of all above adsorbents used for the adsorption studies for the removal of Cr(VI) and phenol from single component and binary solution. Single and multicomponent adsorption iii isotherm models such as Langmuir, Freundlich, Temkin, Redlich, Non modified Langmuir, Modified Langmuir, Extended Langmuir, Extended Freundlich, Non modified Redlich Peterson, Modified Redlich Peterson were applied to the experimental data for the prediction of the adsorption capacity of Cr(VI) and phenol from single and binary solution. The parameters obtained from single component solution were used for the estimation of multicomponent adsorption isotherm parameters. The interactive effect such as synergist and antagonistic was determined for the multicomponent system for simultaneous removal of Cr(VI) and phenol. RSM (Response surface methodology) using Box Behnkin design was also applied to the best adsorbent among binary component system to know the interactive effect of process parameters such as pH, adsorbent dose and contact time and initial concentration of Cr(VI) and phenol. To know the kinetics of adsorption of Cr(VI) and phenol from single and binary solution onto the surface of various adsorbents kinetic models such as pseudo first order, pseudo second order and intra particle diffusion model were applied. The thermodynamic study was carried out for both single and multicomponent system, which showed the feasible and spontaneous nature of the sorption of Cr(VI) and phenol species onto the selected adsorbents. ii) Application of SAB system for single and multicomponent system: Two bacterial strain (Escherichia coli MTCC No. 5041) and (Bacillus sp. MTCC No. 3166) was purchased from MTCC Chandigarh and NCIM pune, India, respectively. The bacterium Escherichia coli and Bacillus sp. was acclimatized to the various concentrations of Cr(VI) and phenol using single and binary synthetic simulated solution prepared in the laboratory. Monod and Haldane kinetics models are used to explain the kinetics of Cr(VI) reduction and Phenol degradation for single component solution. The sum of kinetic model was applied to the binary system for the estimation of interaction parameters for Cr(VI) and phenol. The Bacterial strain Eischerichia coli was capable of removing Cr(VI) while Bacillus sp. was capable of removing both Cr(VI) and phenol from both single and binary solution. SAB studies were performed in batch reactor under optimum conditions of temperature and pH by immobilizing the bacterium onto the surface of best adsorbent (GAC, TW and RH) selected from batch adsorption studies for single component system and (TW) for multiocomponent system. iii) Application of continuous reactor system for simultaneous removal of Cr(VI) and phenol: The continuous reactor study was carried out for simultaneous removal of Cr(VI) and phenol by packing best adsorbent tea waste biomass selected from batch adsorption study in the packed bed column. Various kinetic models such as Adams Bohart, Wolborska and Yoon iv nelson were applied to the experimental data. The bacterium used in SAB study such as Bacillus sp. and Escherichia coli was also immobilized onto the surface of adsorbent bed in packed bed reactor for the simultaneous removal of Cr(VI) and phenol from synthetic simulated waste water prepared in the laboratory. The simultaneous removal of Cr(VI) and phenol from real industrial waste water is also a need of the demand of process industries therefore simultaneous removal from the discharge of effluent of various industries such as tannery, electroplating, pulp and paper is also required. The 99 % removal of Cr(VI) and phenol was obtained at initial concentration of 2000 mg/L of Cr(VI) and 1000 mg/L of phenol by immobilizing bacterial species onto the surface of packed bed. RTD (residence time distribution study) was also carried out to know the deviation from ideal plug flow behaviour of the reactor. The flow model of real reactor is usually lies somewhere between plug flow and mixed flow. The reason for the deviation from the ideal condition is the recycling of the fluid or the creation of stagnant region or channeling of fluid in the reactor. Therefore, the determination of fluid velocity distribution is important for the economic design of the reactor. Consequently, for the velocity distribution better understanding of fluid particles within the reactor to study the distribution of the residence time (RTD) is important because it determines the way in which an individual molecule passes into a reactor. iii) Application of phytoremediation for removal of Cr(VI) and phenol from single and binary solution: Phytoremediation is an alternative technology to remove Cr(VI) and phenol species in contaminated water and soil. In this study the assessment and mechanism for Cr(VI) and phenol species uptake and accumulation in water hyacinth was conducted under optimized hydroponic system. The aquatic macrophyte such as water hyacinth (Eichhornia crassipes) was used for the uptake of two important pollutants Cr(VI) and phenol from single and binary solution. Artificial photosynthesis chamber was used for the growth of plant at 30 ºC and 60% relative humidity. Experiments were carried out at four concentrations 5, 10, 15 and 20 mg/L of Cr(VI) and 10, 20, 30, and 40 mg/L of phenol in both single and binary mixtures of Cr(VI) and phenol, respectively. The FTIR and EDX analysis was carried out to confirm the uptake of Cr(VI) and phenol. The uptake of Cr(VI) was found more in the presence of phenol which shows the synergistic effect for the removal of Cr(VI). It could be because phenol was used as carbon or carbohydrate energy source by the plant at more stressed condition. In case of both single and binary solution, toxic effect was observed at 20 mg/L of Cr(VI). The toxic effect on the plant was determined by estimating chlorophyll, protein and sugar content before and after uptake of Cr(VI) and phenol form single and binary solution. Michaelis-Menten kinetic was applied by calculating the chlorophyll content at different concentration of Cr(VI) and phenol v in single and binary solution to determine the kinetic behaviour of the plant for different growth stages of water hyacinth plant. The residual concentration of Cr(VI) and phenol and chlorophyll content was determined using UV spectrophotometer.