Please use this identifier to cite or link to this item: http://localhost:8081/xmlui/handle/123456789/1363
Title: REMOVAL OF SOME C
Authors: Sharma, Monica
Keywords: CHEMISTRY;ORGANIC TOXIC SUBSTANCES;WATER;INDUSTRIAL WASTE MATERIALS
Issue Date: 2001
Abstract: The rapid industrialization and exhausted exploitation of the natural resources has resulted into the deterioration of the environment to such an extent that the healthy survival of mankind on the earth has become a challenge. Water, in addition to air, is the most important element of life. As a result of its intense use in agriculture, industries, irrigation, cooling and rinsing, the presence of toxic inorganic and organic substances is gradually increasing in surface waters. The removal of toxic pollutants from water is a difficult task because of the diverse number of compounds present and the extremely low concentrations normally encountered. Adsorption process using activated carbon for the removal of organic and inorganic substances has received a widespread attention because of its ability to remove a variety of pollutants. The high cost of carbon treatment and difficulties encountered in its regeneration has grown the interest of researchers in recent to look for other economically feasible alternatives of carbon especially using agricultural and industrial wastes. In India, Sugar and Aluminum industries generate substantial amounts of solid wastes for which disposal is a problem of grave concern. The foremost purpose of the present research is to prepare low cost adsorbents from bagasse fly ash (a sugar industry waste) and red mud (an aluminum industry waste) and to evaluate the physical and chemical parameters for the adsorption of some metal ions, phenols and dyes on these materials. (11) Bagasse fly ash, obtained from a local sugar industry, Iqbalpur (U.P.) was treated with excess hydrogen peroxide (100 volumes) at 60 °C for 24 h, to remove all the adhering impurities. The product so obtained was cooled and washed repeatedly with double distilled water and dried at 100 °C for 24 h in a vacuum oven. The material thus obtained was grounded and sieved to desired particle sizes. The surface area of the activated product was 450 m2g"'. The material was characterized by its chemical composition and X-ray spectra. The resulted product has been used as an adsorbent for the removal of four metal ions (cadmium, nickel, lead and chromium), one phenol (4- chlorophenol) and a dye (fast green). The extent of adsorption at equilibrium is dependent on the physical and chemical characteristics of the adsorbate, adsorbent and other experimental conditions. Batch studies have been performed to establish optimum conditions for the removal of cadmium, nickel, lead and chromium by activated bagasse fly ash. Effect of various parameters like equilibration time, concentration of metal ions, temperature, adsorbent dose, pH and particle size of adsorbent has been studied. The optimum pH values for the removal of cadmium, nickel, lead and chromium were found to be 6.0, 6.5, 6.0 and 5.0 respectively, with 10 g L'1 of the adsorbent (particle size 200-250 BSS mesh). It was observed that cadmium, nickel, chromium and lead are removed up to 90-100 % at lower concentrations (< 1.80xl0"5M for Cd2+, <3.41xl0"5M for Ni2+, < 4.83xlO'5M for Pb "" and < 9.62x10"' M for Cr6+). The percentage removal, however, decreases with increase in concentration of metal ions and finally becomes constant at equilibrium. The uptake increases with increase in temperature for cadmium and nickel, suggesting the endothermic nature of the process. In case of lead and chromium, the uptake decreases (iii) with increase in temperature indicating the process to be exothermic in nature. The presence of other cations and anions affect the removal and uptake goes down by different percentages depending upon the nature of the interferent. The ionic interactions have been interpreted using the ratio of the sorption capacity of the primary ion in the presence of other cations and anions (qm) to that in a single component (q0). The values of qm/q0 in the present studies are < 1 and suggest the suppression of adsorption in the presence of other ions. The adsorption data have been correlated with both Langmuir and Freundlich models The dimensionless constant separation factor RL for all the metal ions is «1 indicating highly favourable nature of the adsorption process. Thermodynamic parameters obtained indicated the feasibility of the process. The kinetic studies provided the necessary mechanistic information of the removal process. It was revealed that the process is quite rapid and equilibrium is attained in 60 minutes for cadmium and chromium and in 80 minutes for nickel and lead. The adsorption was found to follow the film diffusion mechanism at lower concentrations and particle diffusion at higher concentrations. These findings were substantiated by drawing McKay plots. The practical applicability of the product for column operations has also been studied and the removal of these metal ions was achieved up to 90 percent at a flow rate of 0.50 mL/minute. The removal of 4-chlorophenol and fast green was also carried on bagasse fly ash. It is found that uptake of 4-chlorophenol and fast green are exothermic processes and the removal decreases with increase in temperature. 4-chlorophenol and fast green are adsorbed 93.8 % and 99.0 % respectively at lower concentrations (< 1.0x10" M) with optimum bagasse fly ash dose (1.0 g L"1 for 4- chlorophenol and 0.5 g L'1 for fast green) of particle size 150-200 BSS mesh at their optimum pH values (4.0 for 4- chlorophenol and 7.0 for fast green). The percentage adsorption decreases to 72.9% and 89.8 % for 4-chlorophenol and fast green respectively and finally reaches the equilibrium at concentration of 8.0x10"4 M. The data for the adsorption of 4- chlorophenol and fast green fit well into Freundlich and Langmuir models. Thermodynamic parameters of the process have also been evaluated. The Gibbs free energy (AG0) values for both the adsorbates are negative, thereby, indicating the spontaneous nature of the processes. The negative AH" values indicate that the processes are exothermic. The negative AS0 values further support the affinity of bagasse fly ash for 4-chlorophenol and fast green and feasibility of the system. In order to explore some mechanistic aspects, kinetic studies were undertaken on the rate of uptake of 4-chlorophenol and fast green on bagasse fly ash. These indicated the process to be quite rapid and nearly fifty to sixty percent ofthe ultimate adsorption occurs within the first hour of contact. This initial rapid adsorption subsequently gives way to a very slow approach to equilibrium and the saturation is reached in 6-8 hours time. The Bt versus time plot for 4-chlorophenol on bagasse fly ash does not pass through the origin at lower concentration signifying the adsorption to be film diffusion. Further, diffusion coefficient is dependent on concentration of phenol and particle size ofthe adsorbent. This also indicate that film diffusion is operative. However an increase in the sorption rate of 4-chlorophenol with decreasing temperature, support the particle diffusion mechanism. But at higher concentration, initially the Bt versus time plot obtained is linear and passes through the origin and the process seem to be particle diffusion controlled. During the later stages of reactor, the film diffusion mechanism also becomes operative which is apparent from the deviation of plots from linearity. Similarly Bt versus time plot for fast green- fly ash system, does not pass through the origin indicating that the rate controlling process may be film diffusion. Similar plot at higher concentrations initially passes through the origin and has a small slope. In the later portion, the slope increases. At this stage process must not be purely particle diffusion. Further verification to these findings comesfrom McKay plots. The solid waste, red mud was collected from Hindustan Aluminum Company (HINDALCO), Renukoot (Dist. Mirzapur), India. It is formed as a byproduct during the production of alumina from bauxite through the Bayer process. This material was treated with H202 at room temperature for 24 h to oxidize the adhering organic matter and washed repeatedly with double distilled water. The resulting product was dried at 100 °C. The product was cooled and again activated in air at 500 °C for 3h. This material with a surface area of 108 m2g"' gave best surface properties. The material was crushed and sieved to different particle size. The material was characterized by its chemical composition and X-ray spectra. Detailed studies were taken up for the uptake of three dyes (rhodamine B, fast green and methylene blue) and two phenols (4- chlorophenol and 2,4-dinitrophenol) on activated red mud. The uptake of rhodamine B, fast green and methylene blue on red mud was investigated as a function of dye concentration, adsorbent dose, pH, particle size and temperature. The optimum pH values for the removal of rhodamine B, fast green and methylene blue were 1.0, 7.0 and 8.0 respectively. Experiments were conducted with dye solutions of varying concentrations [l.OxlO"5 M to 1.2 xlO"4 M for rhodamine B, l.OxlO'5 Mto l.OxlO"4 M for fast green and l.OxlO"4 Mto l.lxlO'3 M for methylene blue]. A 10 g L"1 of optimum dose of red mud of 150-200 BSS mesh was used for all the experiments. Rhodamine B and fast green were adsorbed 92.5 % and 94.0% respectively at lower concentrations (<_1 OxlO"5 M) while uptake of methylene blue was 75.0 % at lower concentrations (<1.0xl0'4 M). Sorption studies were carried out at 30, 40 and 50 °C to find out the effect of temperature. The decrease in the uptake of dyes in presence of surfactants, both cationic and anionic, has also been described. Adsorption data follow both Langmuir and Freundlich adsorption models. The findings on Freundlich model show that the 'KF' value for the methylene blue is greater than rhodamine B and fast green. Similarly, the adsorption capacity Q° was found to be greater for methylene blue than for the other two dyes. The RL values («1) suggested the adsorption of dyes to be favourable on the adsorbent. The thermodynamic parameters were evaluated and are in confirmation of the affinity of adsorbent material towards dyes. The equilibrium kinetic studies performed for the adsorption of the dyes on red mud indicated the process to be quite rapid and typically fifty to sixty percent of the ultimate adsorption occurs within the first hour of contact. The initial rapid adsorption subsequently gives way to a very slow approach to equilibrium and saturation is reached in 8-10 h time. Relevant parameters such as diffusion coefficient, activation energy and entropy of the processes have also been calculated. The uptake of two phenols viz. 4-chlorophenol and 2,4-dinitrophenol was also investigated on activated red mud. Several factors affecting their uptake from water (e.g., concentration of adsorbate, temperature, adsorbent dose, particle size of the adsorbent, etc.) have been studied at the optimum pH (4.0 for 2,4-dinitrophenol and 7.0 for 4-chlorophenol). Adsorption isotherms for 2,4-dinitrophenol and 4-chlorophenol were run at concentrations ranging between l.OxlO"5 Mto l.lxl0'4 Mat an optimum red mud dose of 10 g L"1 (150-200 BSS mesh) at 30 °C. The removal of 2,4-dinitrophenol and 4-chlorophenol was 94.2 % and 97.1 % respectively at lower concentrations while it decreases to 84.6 % and 73.5 % at equilibrium concentrations (8.0xl0"5 M). The removal decreases with increasing temperature for both the phenols suggesting the exothermic nature of the sorption process. Thermodynamic parameters were calculated using the Langmuir and Freundlich models. It is observed that KF and Q° values are more for 2,4-dinitrophenol-red mud system. The Langmuir constant Q° decreases with increase in temperature, indicating the exothermic nature of the process. The values of dimensionless separation factor, 'R|,' are «1, which indicates favourable adsorption for both the systems. Negative free energy values indicated the feasibility and spontaneous nature of the process. Negative AH0 values depicted the process to be exothermic in nature. Negative values of entropy (AS0) of adsorption, reflected the affinity of red mud for the phenols. Kinetic studies provided the necessary mechanistic information for the removal process. The equilibrium is attained in eight and five hours for 4-chlorophenol and 2,4- dinitrophenol respectively. Values of diffusion coefficient, activation energy and entropy of the process calculated from the kinetic studies have also been given. The effect on the uptake of phenols in the presence of cationic and anionic surfactants (cetyltrimethyl ammonium bromide and manoxol IB) is also carried out. A comparison of dye and phenol removal by bagasse fly ash and red mud indicated that bagasse fly ash is better adsorbent than red mud. The costs of activated bagasse fly ash and activated red mud were estimated considering all the factors. The finished bagasse fly ash costs -US$12 ton"' and red mud -US$30 ton"'. In contrast,the cheapest variety of commercially available carbon costs -US$285 ton"'. Looking into the scavenging capacity of the developed products, it may be concluded that the proposed adsorbents may be good replacements for expensive commercially available carbon due to their low cost and good removal efficiency.
URI: http://hdl.handle.net/123456789/1363
Other Identifiers: Ph.D
Research Supervisor/ Guide: Gupta, V. K.
metadata.dc.type: Doctoral Thesis
Appears in Collections:DOCTORAL THESES (chemistry)

Files in This Item:
File Description SizeFormat 
REMOVAL OF SOME TOXIC SUBSTANCES FROM AQUEOUS SOLUTIONS USING INDUSTRIAL WASTES.pdf9.91 MBAdobe PDFView/Open


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.