Title of Invention	PROCESS FOR REMOVAL OF HEAVY METAL IONS AND DYES IN WATER WITH NEEM LEAF POWDER AS AN ADSORBENT
Abstract	A process is described for preparing an adsorbent, NLP, from the mature Neem (Azadirachta indica) leaves. The NLP is very effective in treating water contaminated with various dyes and heavy metals. The adsorbent can be regenerated and is reusable. Experiments conducted to remove a series of dyes like Methylene Blue, Congo Red, Brilliant Green, etc., and toxic metals like Chromium (VI) and Cadmium(II), have shown that the powder has 100 % removal efficiency depending on the amount used and the concentration of the contaminant. It is claimed that the NLP can be a very economical green alternative to replace various commercial adsorbents like activated carbon in tertiary treatment of industrial effluents for removal of dyes and pigments, and metals. The NLP acts synergistically to remove pollutants from water.

Title of Invention

PROCESS FOR REMOVAL OF HEAVY METAL IONS AND DYES IN WATER WITH NEEM LEAF POWDER AS AN ADSORBENT

Abstract

A process is described for preparing an adsorbent, NLP, from the mature Neem (Azadirachta indica) leaves. The NLP is very effective in treating water contaminated with various dyes and heavy metals. The adsorbent can be regenerated and is reusable. Experiments conducted to remove a series of dyes like Methylene Blue, Congo Red, Brilliant Green, etc., and toxic metals like Chromium (VI) and Cadmium(II), have shown that the powder has 100 % removal efficiency depending on the amount used and the concentration of the contaminant. It is claimed that the NLP can be a very economical green alternative to replace various commercial adsorbents like activated carbon in tertiary treatment of industrial effluents for removal of dyes and pigments, and metals. The NLP acts synergistically to remove pollutants from water.

Full Text	Title Process for removal of heavy metal ions and dyes in water with Neem Leaf Powder as an adsorbent Applicants (i) Arunima Sarma Research Fellow, Department of Chemistry Gauhati University, Guwahati 781014, Assam [Nationality: Indian] (ii) Krishna Gopal Bhattacharyya Professor & Head, Department of Chemistry Gauhati University, Guwahati 781914, Assam [Nationality: Indian] The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed. 1 1) Title of invention: Process for removal of contaminants from water with Neem Leaf Powder as an adsorbent 2) Field of invention: Chemistry 3) Background of invention: Adsorption technology is one of the superior techniques for the treatment of industrial effluents. The suitability of an adsorbent for an adsorption process in a commercial separation or purification of effluents depends on the thermodynamic equilibrium for each adsorbate-adsorbent interaction, kinetic effect, intra-particle diffusion of adsorbate on the adsorbent and desorption effect. Such a highly porous solid may be carbonaceous or inorganic in nature, synthetic or naturally occurring and in certain circumstances may have true molecular sieving properties. The adsorbent must also have good mechanical properties such as strength and resistance to attrition and it must have good kinetic properties, that is, it must be capable of transferring adsorbing molecules rapidly to the adsorption sites. In most applications the adsorbent must be regenerated after use and therefore it is desirable that regeneration can be carried out efficiently and without damage to mechanical and adsorptive properties. The raw materials and methods for producing adsorbent must ultimately be inexpensive for adsorption to compete successfully on economic grounds with alternative separation processes. With the objective to prepare a cheap alternative adsorbent to activated carbon, for removal of micro-pollutants, which normally resist biological treatment, the present adsorbent has been developed. 4) Object of invention: The principal object of this invention is to prepare an adsorbent in the form of a powder from the mature leaves of the Neem Tree (Azadirachta indica) for removing pollutants from water. 5) A summary of invention: An adsorbent in the form of a powder is prepared from mature Neem (Azadirachta indica) leaves. The powder is found to be very effective in treating water contaminated with various dyes and heavy metals. The adsorbent can be regenerated and is reusable. Experiments conducted to remove a series of dyes, Methylene Blue, Congo Red, Brilliant Green, etc., and toxic metals like Chromium (VI) and Cadmium(II), have shown that 2 the powder has 100 % removal efficiency depending on the amount used and the concentration of the contaminant. It is claimed that the Neem leaf powder can be a very economical green alternative to replace various commercial adsorbents like activated carbon in tertiary treatment of industrial effluents for removal of dyes and pigments, and metals. 6) A brief description of the accompanying drawing: Does not arise 7) Detailed description: The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed. Preparation of the Neem Leaf Powder (NLP) The adsorbent based on Neem (Azadirachta indica) leaves is prepared as follows: Mature Neem leaves, collected from a number of tall Neem trees are washed repeatedly with water to remove dust and soluble impurities and are allowed to dry first at room temperature (298 ± 2 K) in a shade and then in an air oven at 333 - 343 K for a long time till the leaves became crisp that could be crushed into a fine powder in a mechanical grinder. The Neem Leaf Powder (NLP) is then sieved and the 200-300-mesh fraction is separated. This fraction is again washed a number of times with double distilled water till the washings are free of color and turbidity. After drying for several hours at room temperature, the Neem Leaf Powder (NLP) is ready for use and it is preserved in glass bottles. The NLP can be used as an efficient adsorbent for dyes & pigments, and also metals. Examples (i) Adsorption of Methylene Blue The 200-300 mesh fraction could be used as an adsorbent for removal of colour due to the dye Methylene Blue in aqueous medium. In a typical batch adsorption study, Neem Leaf Powder (NLP) was used in the amount of 2.0 to 6.0 g/L to remove the dye from aqueous solution of 3 concentration, 25 - 75 mg/L, in contact time of 1 - 5 hours and varying the pH of the medium from 2.0 - 10.0. It was possible to remove 85.0 to 91.7 % of the dye after treatment for just 1 hour. 100 % removal is possible either by taking concentration of the dye less than 25 mg/L or by increasing the NLP amount. The adsorption data closely followed the adsorption isotherms due to both Freundlich and Langmuir. The values of the adsorption coefficients agreed well with equilibrium considerations for a successful adsorbent: Freundlich adsorption affinity - 0.51 to 0.68 for the different adsorbent amounts with the adsorption capacity values in the range of 2.51 to 9.49 dm3 g-1; Langmuir monolayer capacity values = 9.80 to 44.84 mg g-1 and Langmuir adsorption intensity values = 0.23 to 0.33 dm3 g-1. These values suggest that the use of NLP as an adsorbent is energetically favourable. That the process is supported by thermodynamic considerations is demonstrated by experimental determination of changes in enthalpy, entropy and Gibbs energy for the adsorption process at five different temperatures from 300 to 340 K at an interval of 10°. The enthalpy of adsorption had values from 6.30 to 24.86 kJ mol-1 with a mean value of 11.43 kJ mol-1 at the above temperature range. The adsorption entropy varied from 59.66 and 116.32 J mol-1 K-1 and the Gibbs energy varied from - 12.54 to - 14.26 kJ mol-1 at the same temperature change. The adsorption process on NLP followed first order kinetics with a rate constant of 2.76 x 10-3 to 5.07 x 10-3 min-1. The whole process was very fast and adsorption of the dye was nearly complete in just 1 hour. (ii) Adsorption of Congo red The NLP is almost equally effective as an adsorbent for removing the dye Congo Red from aqueous medium. A series of experiments were conducted with the dye concentration of 20 to 60 mg/L and using NLP amounts from 0.2 to 1.0 g/L. In the range of NLP amounts, 35.0 to 49.9 % of the dye could be removed in 1 hour treatment time from a Congo Red solution of concentration 40 mg/L. For the same amounts of NLP, the removal efficiency increased from 62.5 to 95.0 % if the treatment time is increased to 5 hours. Increasing the amount of NLP, 100 % removal of the dye was possible. 88 to 100 % of the dye could be removed from an aqueous solution of concentration 20 mg/L if the amount of NLP was increased from 0.2 to 1.0 g/L with a treatment time of 4 hours. Langmuir and Freundlich isotherms for the adsorption equilibrium yield perfect fits with very 4 high regression coefficient. The adsorption coefficients were perfectly compatible with NLP being a highly potent adsorbent: Freundlich adsorption affinity = 0.1214 to 0.1877 and adsorption capacity = 0.1039 to 0.2648 dm3 g-1 Langmuir monolayer coverage = 0.0592 to 0.1841 mmol g-1 and adsorption intensity = 443.3 to 603.5 dm3 mmol-l. All these values favoured the equilibrium NLP + dye = [NLP-dye complex] shifting largely to the right. Values of thermodynamic parameters, enthalpy change, entropy change and Gibbs energy change are the actual indicators for practical application of a process and these very well support the above equilibrium. The values obtained for the thermodynamic parameters for adsorption of the dye on NLP in the temperature range, 303 to 323 K, indicated the process to be exothermic with heats of adsorption values in the range -7.92 to -18.70 kJ mol-1 for the given concentration range of the dye solution. The Gibbs energy change was in the range of-1.09 to -1.81 kJ mol-1 and the entropy change was in the range of-18.97 to -56.32 J mol-1 KT . The kinetics of the adsorption process were of first order with a rate constant of 1.77 x 10-4 s-1. The intra- particle diffusion rate constant in the range 2.6 x 10-2 - 4.5 x 10-2 mmol g-1 min-1/2 showed that after the comparatively fast adsorption of the dye on NLP particles, there was a slow second order intra-particle diffusion. (iii) Adsorption of Brilliant Green The dye Brilliant Green also adsorbs very well on the Neem Leaf Powder (NLP). The adsorption experiments were conducted in the concentration range of 10-50 mg/L at four different temperatures of 300, 303, 313 and 323 K with NLP amounts of 0.13 to 0.63 g/L. In a contact time of just 1 hour, 0.13 g NLP could remove 35 % of the dye from an aqueous dye solution of concentration 40 mg/L. The adsorption increases to 71.8 % after 5 hours. If the NLP amount was increased to 0.63 g/L, the removal of the dye increased to 98 %. The adsorption was enhanced if the temperature of adsorption was a little above the ambient temperature. The enthalpy of adsorption in the temperature range, 300 to 323 K varied between 5.66 to 17.64 kJ mol-1 with a mean value of 12.12 kJ mol"1. The adsorption was accompanied by an average entropy increase of 61.02 J mol-1 K-1 which showed that the adsorbed dye molecules were organized in a much more random fashion on the surface of the NLP particles compared to the situation in the aqueous phase. The Gibbs energy decreased 5 due to adsorption of the dye indicating the process to be spontaneous and thermodynamically feasible. The equilibrium Brilliant Green + NLP = Brilliant Green NLP was favoured in the forward direction. The values of the adsorption coefficients, calculated from Langmuir and Freundlich equations, showed that the Langmuir monolayer capacity varied from 0.149 to 0.554 mmol g-1, adsorption affinity varied from 1.046 to 5.98 L mmol-1, Freundlich adsorption intensity from 0,42 to 0.49, and adsorption capacity from 1.04 to 2.36 L g-1. The first order rate constant for adsorption of the dye Brilliant green on NLP had the mean value of 7.32 x 10-3 min-1, which may be considered as sufficiently fast to exploit the process for practical applications. The intra-particle diffusion rate has the value of 8.12 x 10-4 mmol g-1 min-1/2, showing that while the adsorption of the dye on the surface of the NLP particles was quite fast, the intra-particle diffusion was slower by a factor of nearly 10. (iv) Adsorption of Chromium (VI) Cr (VI) is a toxic metal. It was seen that NLP was a very good non-conventional adsorbent for the ions of this metal in aqueous solution. An amount of 14 g NLP was sufficient to remove l00 % of Cr(VI) from a solution containing 20 mg Cr (VI) per litre. The equilibrium was reached in about 3 hours. The kinetics of Cr (VI) adsorption on different amounts of NLP followed the first order kinetics given by Lagergren equation. The first order rate constant was calculated from the linear least-square method and the values remained in the range of 5.07 x 10-3 min-1 to 17.96 x 10-3 min-1. The intra-particle diffusion rate constant was 4.83 x 10-4 meq g-1 min-1/2, which was much smaller compared to the initial rate of adsorption. The solution pH was one of the parameters influencing adsorption of metallic ions. For 6 adsorption of Cr (VI) the maximum adsorption (82.5 %) of Cr (VI) occurred at pH 5.5. The temperature played a vital role in the adsorption process. The adsorption capacity of NLP for chromium decreased with increase in temperature. The adsorption isotherms were measured at a constant contact time of 3 h at room temperature with different amounts (1.6 to 14 g/L) of NLP and at Cr (VI) concentration of 20 to 70 mg/L. The adsorption process was found to fit well with the Freundlich and the Langmuir isotherms with good correlation factor. The isotherm constants indicate a favourable adsorption process. The Freundlich constants had the values 0.31 to 0.58 (adsorption intensity), 0.15 to 1.38 L g-1 (adsorption capacity) and the Langmuir constants 0.10 to 1.01 meq g-1 (monolayer adsorption capacity), 6.04 to 39.12 L meq-1 (adsorption affinity). This values show that the adsorption of Cr (VI) on NLP can have practical application. The adsorption experiments were also carried out at three different temperatures of 27, 40, and 50°C with a fixed amount of 6.0 g NLP per litre at a constant contact time of 3 h. The enthalpy of adsorption in this temperature ranges varied between - 58.61 to - 65.65 kj mol-1 . The adsorption interaction is exothermic in nature. The adsorption process was accompanied by a nearly constant entropy change (- 13.72 x 102 K-1 to - 15.82 x 10-2 kj mol-1 K-1). The Gibbs energy change for the adsorption process was from - 14.03 to -17.45 kj mol-1, which is not very large, but the negative values support the forward direction of the equilibrium Cr(VI)+ NLP = Cr(VI) NLP. (v) Adsorption of Cadmium (II) The Cd (II) adsorbs also very well on the non-conventional NLP adsorbent. The amount of adsorption was as large as 97 to 100 % for a solution containing 100 mg Cd (II) per litre with a NLP amount of varying between 0.4 to 1.6 g/L. The experimental results show that the equilibrium was reached at 3 h in most cases. The maximum adsorption of Cd (H) occurred at pH 6.0. 7 We claim:- A process for removing contaminating heavy metal ions and dyes such as herein described in water comprising treating the contaminated water with Neem leaf powder (NLP) as adsorbent. The process as claimed in Claim 1 wherein the contaminant is methylene blue and Neem leaf powder (NLP) is used for 100 % removal from aqueous solution containing 20 mg of the dye in 1 litre of water using 6.0 g of Neem leaf powder (NLP). The process as claimed in Claim 1, wherein the contaminant is Congo Red and Neem leaf powder (NLP) is used for 95 % removal from aqueous solution containing 60 mg of the dye in 1 litre of water using 1.0 g of Neem leaf powder (NLP). The process as claimed in Claim 1 wherein the contaminant is Brilliant Green and Neem leaf powder (NLP) is used for 98 % removal from aqueous solution containing 40 mg of the dye in 1 litre of water using 0.63 g of Neem leaf powder (NLP). The process as claimed in Claim 1 wherein the contaminant is Cr(VT) ions and Neem leaf powder (NLP) is used for 100 % removal from aqueous solution containing 20 mg of the Cr(VI) ions in 1 litre of water using 14.0 g of Neem leaf powder (NLP). The process as claimed in Claim 1 wherein the contaminant is Cd(II) ions and Neem leaf powder (NLP) is used for 100 % removal from aqueous solution containing 100 8 mg of the Cd(II) ions in 1 litre of water using 1.6 g of Neem leaf powder (NLP). A process is described for preparing an adsorbent, NLP, from the mature Neem (Azadirachta indica) leaves. The NLP is very effective in treating water contaminated with various dyes and heavy metals. The adsorbent can be regenerated and is reusable. Experiments conducted to remove a series of dyes like Methylene Blue, Congo Red, Brilliant Green, etc., and toxic metals like Chromium (VI) and Cadmium(II), have shown that the powder has 100 % removal efficiency depending on the amount used and the concentration of the contaminant. It is claimed that the NLP can be a very economical green alternative to replace various commercial adsorbents like activated carbon in tertiary treatment of industrial effluents for removal of dyes and pigments, and metals. The NLP acts synergistically to remove pollutants from water.

Full Text

Title
Process for removal of heavy metal ions and dyes in water with Neem Leaf Powder as an
adsorbent
Applicants
(i) Arunima Sarma
Research Fellow, Department of Chemistry
Gauhati University, Guwahati 781014, Assam [Nationality: Indian]
(ii) Krishna Gopal Bhattacharyya
Professor & Head, Department of Chemistry Gauhati University, Guwahati 781914, Assam [Nationality: Indian]
The following specification particularly describes and ascertains the nature of this invention and the manner in which it is to be performed.
1

1) Title of invention: Process for removal of contaminants from water with Neem Leaf
Powder as an adsorbent
2) Field of invention: Chemistry
3) Background of invention: Adsorption technology is one of the superior techniques for the
treatment of industrial effluents. The suitability of an adsorbent for an adsorption process in a
commercial separation or purification of effluents depends on the thermodynamic equilibrium
for each adsorbate-adsorbent interaction, kinetic effect, intra-particle diffusion of adsorbate on
the adsorbent and desorption effect. Such a highly porous solid may be carbonaceous or
inorganic in nature, synthetic or naturally occurring and in certain circumstances may have
true molecular sieving properties. The adsorbent must also have good mechanical properties
such as strength and resistance to attrition and it must have good kinetic properties, that is, it
must be capable of transferring adsorbing molecules rapidly to the adsorption sites. In most
applications the adsorbent must be regenerated after use and therefore it is desirable that
regeneration can be carried out efficiently and without damage to mechanical and adsorptive
properties. The raw materials and methods for producing adsorbent must ultimately be
inexpensive for adsorption to compete successfully on economic grounds with alternative
separation processes. With the objective to prepare a cheap alternative adsorbent to activated
carbon, for removal of micro-pollutants, which normally resist biological treatment, the
present adsorbent has been developed.
4) Object of invention:
The principal object of this invention is to prepare an adsorbent in the form of a powder from the mature leaves of the Neem Tree (Azadirachta indica) for removing pollutants from water.
5) A summary of invention: An adsorbent in the form of a powder is prepared from mature
Neem (Azadirachta indica) leaves. The powder is found to be very effective in treating water
contaminated with various dyes and heavy metals. The adsorbent can be regenerated and is
reusable. Experiments conducted to remove a series of dyes, Methylene Blue, Congo Red,
Brilliant Green, etc., and toxic metals like Chromium (VI) and Cadmium(II), have shown that
2

the powder has 100 % removal efficiency depending on the amount used and the concentration of the contaminant. It is claimed that the Neem leaf powder can be a very economical green alternative to replace various commercial adsorbents like activated carbon in tertiary treatment of industrial effluents for removal of dyes and pigments, and metals.
6) A brief description of the accompanying drawing:
Does not arise
7) Detailed description: The following specification particularly describes and ascertains the
nature of this invention and the manner in which it is to be performed.
Preparation of the Neem Leaf Powder (NLP)
The adsorbent based on Neem (Azadirachta indica) leaves is prepared as follows:
Mature Neem leaves, collected from a number of tall Neem trees are washed repeatedly with water to remove dust and soluble impurities and are allowed to dry first at room temperature (298 ± 2 K) in a shade and then in an air oven at 333 - 343 K for a long time till the leaves became crisp that could be crushed into a fine powder in a mechanical grinder. The Neem Leaf Powder (NLP) is then sieved and the 200-300-mesh fraction is separated. This fraction is again washed a number of times with double distilled water till the washings are free of color and turbidity. After drying for several hours at room temperature, the Neem Leaf Powder (NLP) is ready for use and it is preserved in glass bottles. The NLP can be used as an efficient adsorbent for dyes & pigments, and also metals.
Examples
(i) Adsorption of Methylene Blue
The 200-300 mesh fraction could be used as an adsorbent for removal of colour due to the dye Methylene Blue in aqueous medium. In a typical batch adsorption study, Neem Leaf Powder (NLP) was used in the amount of 2.0 to 6.0 g/L to remove the dye from aqueous solution of
3

concentration, 25 - 75 mg/L, in contact time of 1 - 5 hours and varying the pH of the medium from 2.0 - 10.0. It was possible to remove 85.0 to 91.7 % of the dye after treatment for just 1 hour. 100 % removal is possible either by taking concentration of the dye less than 25 mg/L or by increasing the NLP amount. The adsorption data closely followed the adsorption isotherms due to both Freundlich and Langmuir. The values of the adsorption coefficients agreed well with equilibrium considerations for a successful adsorbent: Freundlich adsorption affinity - 0.51 to 0.68 for the different adsorbent amounts with the adsorption capacity values in the range of 2.51 to 9.49 dm3 g-1; Langmuir monolayer capacity values = 9.80 to 44.84 mg g-1 and Langmuir adsorption intensity values = 0.23 to 0.33 dm3 g-1. These values suggest that the use of NLP as an adsorbent is energetically favourable. That the process is supported by thermodynamic considerations is demonstrated by experimental determination of changes in enthalpy, entropy and Gibbs energy for the adsorption process at five different temperatures from 300 to 340 K at an interval of 10°. The enthalpy of adsorption had values from 6.30 to 24.86 kJ mol-1 with a mean value of 11.43 kJ mol-1 at the above temperature range. The adsorption entropy varied from 59.66 and 116.32 J mol-1 K-1 and the Gibbs energy varied from - 12.54 to - 14.26 kJ mol-1 at the same temperature change. The adsorption process on NLP followed first order kinetics with a rate constant of 2.76 x 10-3 to 5.07 x 10-3 min-1. The whole process was very fast and adsorption of the dye was nearly complete in just 1 hour.
(ii) Adsorption of Congo red
The NLP is almost equally effective as an adsorbent for removing the dye Congo Red from aqueous medium. A series of experiments were conducted with the dye concentration of 20 to 60 mg/L and using NLP amounts from 0.2 to 1.0 g/L. In the range of NLP amounts, 35.0 to 49.9 % of the dye could be removed in 1 hour treatment time from a Congo Red solution of concentration 40 mg/L. For the same amounts of NLP, the removal efficiency increased from 62.5 to 95.0 % if the treatment time is increased to 5 hours. Increasing the amount of NLP, 100 % removal of the dye was possible. 88 to 100 % of the dye could be removed from an aqueous solution of concentration 20 mg/L if the amount of NLP was increased from 0.2 to 1.0 g/L with a treatment time of 4 hours.
Langmuir and Freundlich isotherms for the adsorption equilibrium yield perfect fits with very
4

high regression coefficient. The adsorption coefficients were perfectly compatible with NLP being a highly potent adsorbent: Freundlich adsorption affinity = 0.1214 to 0.1877 and adsorption capacity = 0.1039 to 0.2648 dm3 g-1 Langmuir monolayer coverage = 0.0592 to 0.1841 mmol g-1 and adsorption intensity = 443.3 to 603.5 dm3 mmol-l. All these values favoured the equilibrium NLP + dye = [NLP-dye complex] shifting largely to the right. Values of thermodynamic parameters, enthalpy change, entropy change and Gibbs energy change are the actual indicators for practical application of a process and these very well support the above equilibrium. The values obtained for the thermodynamic parameters for adsorption of the dye on NLP in the temperature range, 303 to 323 K, indicated the process to be exothermic with heats of adsorption values in the range -7.92 to -18.70 kJ mol-1 for the given concentration range of the dye solution. The Gibbs energy change was in the range of-1.09 to -1.81 kJ mol-1 and the entropy change was in the range of-18.97 to -56.32 J mol-1 KT . The kinetics of the adsorption process were of first order with a rate constant of 1.77 x 10-4 s-1. The intra- particle diffusion rate constant in the range 2.6 x 10-2 - 4.5 x 10-2 mmol g-1 min-1/2 showed that after the comparatively fast adsorption of the dye on NLP particles, there was a slow second order intra-particle diffusion.
(iii) Adsorption of Brilliant Green
The dye Brilliant Green also adsorbs very well on the Neem Leaf Powder (NLP). The adsorption experiments were conducted in the concentration range of 10-50 mg/L at four different temperatures of 300, 303, 313 and 323 K with NLP amounts of 0.13 to 0.63 g/L. In a contact time of just 1 hour, 0.13 g NLP could remove 35 % of the dye from an aqueous dye solution of concentration 40 mg/L. The adsorption increases to 71.8 % after 5 hours. If the NLP amount was increased to 0.63 g/L, the removal of the dye increased to 98 %.
The adsorption was enhanced if the temperature of adsorption was a little above the ambient temperature. The enthalpy of adsorption in the temperature range, 300 to 323 K varied between 5.66 to 17.64 kJ mol-1 with a mean value of 12.12 kJ mol"1. The adsorption was accompanied by an average entropy increase of 61.02 J mol-1 K-1 which showed that the adsorbed dye molecules were organized in a much more random fashion on the surface of the NLP particles compared to the situation in the aqueous phase. The Gibbs energy decreased
5

due to adsorption of the dye indicating the process to be spontaneous and thermodynamically feasible. The equilibrium
Brilliant Green + NLP = Brilliant Green NLP was favoured in the forward direction.
The values of the adsorption coefficients, calculated from Langmuir and Freundlich equations, showed that the Langmuir monolayer capacity varied from 0.149 to 0.554 mmol g-1, adsorption affinity varied from 1.046 to 5.98 L mmol-1, Freundlich adsorption intensity from 0,42 to 0.49, and adsorption capacity from 1.04 to 2.36 L g-1.
The first order rate constant for adsorption of the dye Brilliant green on NLP had the mean value of 7.32 x 10-3 min-1, which may be considered as sufficiently fast to exploit the process for practical applications. The intra-particle diffusion rate has the value of 8.12 x 10-4 mmol g-1 min-1/2, showing that while the adsorption of the dye on the surface of the NLP particles was quite fast, the intra-particle diffusion was slower by a factor of nearly 10.
(iv) Adsorption of Chromium (VI)
Cr (VI) is a toxic metal. It was seen that NLP was a very good non-conventional adsorbent for the ions of this metal in aqueous solution. An amount of 14 g NLP was sufficient to remove l00 % of Cr(VI) from a solution containing 20 mg Cr (VI) per litre. The equilibrium was reached in about 3 hours.
The kinetics of Cr (VI) adsorption on different amounts of NLP followed the first order kinetics given by Lagergren equation. The first order rate constant was calculated from the linear least-square method and the values remained in the range of 5.07 x 10-3 min-1 to 17.96 x 10-3 min-1. The intra-particle diffusion rate constant was 4.83 x 10-4 meq g-1 min-1/2, which was much smaller compared to the initial rate of adsorption.
The solution pH was one of the parameters influencing adsorption of metallic ions. For
6

adsorption of Cr (VI) the maximum adsorption (82.5 %) of Cr (VI) occurred at pH 5.5.
The temperature played a vital role in the adsorption process. The adsorption capacity of NLP for chromium decreased with increase in temperature. The adsorption isotherms were measured at a constant contact time of 3 h at room temperature with different amounts (1.6 to 14 g/L) of NLP and at Cr (VI) concentration of 20 to 70 mg/L. The adsorption process was found to fit well with the Freundlich and the Langmuir isotherms with good correlation factor. The isotherm constants indicate a favourable adsorption process. The Freundlich constants had the values 0.31 to 0.58 (adsorption intensity), 0.15 to 1.38 L g-1 (adsorption capacity) and the Langmuir constants 0.10 to 1.01 meq g-1 (monolayer adsorption capacity), 6.04 to 39.12 L meq-1 (adsorption affinity). This values show that the adsorption of Cr (VI) on NLP can have practical application.
The adsorption experiments were also carried out at three different temperatures of 27, 40, and 50°C with a fixed amount of 6.0 g NLP per litre at a constant contact time of 3 h. The enthalpy of adsorption in this temperature ranges varied between - 58.61 to - 65.65 kj mol-1 . The adsorption interaction is exothermic in nature. The adsorption process was accompanied by a nearly constant entropy change (- 13.72 x 102 K-1 to - 15.82 x 10-2 kj mol-1 K-1). The Gibbs energy change for the adsorption process was from - 14.03 to -17.45 kj mol-1, which is not very large, but the negative values support the forward direction of the equilibrium
Cr(VI)+ NLP = Cr(VI) NLP.
(v) Adsorption of Cadmium (II)
The Cd (II) adsorbs also very well on the non-conventional NLP adsorbent. The amount of adsorption was as large as 97 to 100 % for a solution containing 100 mg Cd (II) per litre with a NLP amount of varying between 0.4 to 1.6 g/L.
The experimental results show that the equilibrium was reached at 3 h in most cases. The maximum adsorption of Cd (H) occurred at pH 6.0.
7

We claim:-
A process for removing contaminating heavy metal ions and dyes such as herein
described in water comprising treating the contaminated water with Neem leaf powder
(NLP) as adsorbent.
The process as claimed in Claim 1 wherein the contaminant is methylene blue and
Neem leaf powder (NLP) is used for 100 % removal from aqueous solution containing
20 mg of the dye in 1 litre of water using 6.0 g of Neem leaf powder (NLP).
The process as claimed in Claim 1, wherein the contaminant is Congo Red and Neem
leaf powder (NLP) is used for 95 % removal from aqueous solution containing 60 mg
of the dye in 1 litre of water using 1.0 g of Neem leaf powder (NLP).
The process as claimed in Claim 1 wherein the contaminant is Brilliant Green and
Neem leaf powder (NLP) is used for 98 % removal from aqueous solution containing
40 mg of the dye in 1 litre of water using 0.63 g of Neem leaf powder (NLP).
The process as claimed in Claim 1 wherein the contaminant is Cr(VT) ions and Neem
leaf powder (NLP) is used for 100 % removal from aqueous solution containing 20 mg
of the Cr(VI) ions in 1 litre of water using 14.0 g of Neem leaf powder (NLP).
The process as claimed in Claim 1 wherein the contaminant is Cd(II) ions and Neem
leaf powder (NLP) is used for 100 % removal from aqueous solution containing 100
8
mg of the Cd(II) ions in 1 litre of water using 1.6 g of Neem leaf powder (NLP).
A process is described for preparing an adsorbent, NLP, from the mature Neem (Azadirachta indica) leaves. The NLP is very effective in treating water contaminated with various dyes and heavy metals. The adsorbent can be regenerated and is reusable. Experiments conducted to remove a series of dyes like Methylene Blue, Congo Red, Brilliant Green, etc., and toxic metals like Chromium (VI) and Cadmium(II), have shown that the powder has 100 % removal efficiency depending on the amount used and the concentration of the contaminant. It is claimed that the NLP can be a very economical green alternative to replace various commercial adsorbents like activated carbon in tertiary treatment of industrial effluents for removal of dyes and pigments, and metals. The NLP acts synergistically to remove pollutants from water.

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201371

Indian Patent Application Number

200/KOL/2003

PG Journal Number

07/2007

Publication Date

16-Feb-2007

Grant Date

16-Feb-2007

Date of Filing

04-Apr-2003

Name of Patentee

ARUNIMA SARMA

Applicant Address

GAUHATI UNIVERSITY GUWAHATI 781014

Inventors:

#	Inventor's Name	Inventor's Address
1	ARUNIMA SARMA	RESEARCH FELLOW, DEPT.OF CHEMISTRY GAUHATI UNIVERSITY GUWAHATI 781014
2	KRISHNA GOPAL BHATTACHARJEE	PROFESSOR & HEAD,DEPARTMENT OF CHEMISTRY GAUHATI UNIVERSITY,GUWAHATI 781919

PCT International Classification Number

B01 D15/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA