removal of Zn, Cd and Pb from pulp and paper mill effluents BY MANGO PLANT LEAVS (MPL)

P.M. Yeole^2* and V.S. Shrivastava^1*

¹Centre for P.G. Research in Chemistry, G.T.P. College, Nandurbar 425 412, M.S., India

²R.L. College, Parola 425 111, M.S., India

*Corresponding Author:

P.M. Yeole
E:mail: Pmy_chem@rocketmail.com

V.S. Shrivastava
E:mail: drvind_shrivastava@yahoo.com

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Abstract

Mango plant leaves were found to have natural capacity to accumulte heavy metals at significant concentration. Phytoremediation or biosorption for a new technology is aimed at removing these metals from dilute solutions or from the industrial waste like pulp and paper mill wastewater.The concentration of these metals was determined by ICP-AES. The method also indicated that the order of adsorption affinity was Pb2+>Cd2+>Zn2+, respectively.

Keywords

Removal, Metals, Mango plant leaves, Biosorption.

Introduction

Hazardous metal ions, specially, Zn, Cd and Pb have become prominent pollutants. Even the traces of these metal ions present in different types of waters may prove highly toxic (Forster and Salomons, 1980; Sterritt and Lester, 1980). The concentration of these metal ions is increased in waters by different types of human activites like mine drainages, industrial effluents, acid rain etc. Their removal from water is hence, significant and to meet these a large number of methods have been suggested. In the present method the mango plant leaves(MPL) has been used for the removal of Zn²⁺,Cd²⁺ and Pb²⁺. Some other workers (3-4) have also used plant substrates to remove different types of contaminants.

Materials and Methods

Mango plant leaves were collected from near by areas. These leaves was dried four hours in an oven at 60°C and finally powdered to give size to the sample particles between .075mm and .250mm. Dry powder of MPL was used for the bioadsorption (removal) studies.

Stock solutions (10000 ppm) of Zn²⁺ Cd²⁺ and Pb²⁺ were prepared in conductivity water. The solution pH was adjusted with HCL and NaoH. Exactly 100mL of sample solutions were taken into beakers containing 1gm of plant substrate. Each system was stirred for specific period of time. After stirring the samples were filtered. The filtrate was heated with 5mL of concentrated HNO3 and evaporated to near dryness on water bath. The residue was dissolved in 3mL conc HCL by slight warming made to volume and filtered to remove any insoluble material. The extract was analysed for Pb, Cd and Zn concentration by ICP-AES at Sophisticated Analytical instrument Facility (SAIF)IIT, Mumbai.

Results and Discussion

The experimental analsis was conducted to determine the actual amount of metals bound to MPL powder as wel l as the influence of pH upon binding of Zn²⁺, Cd²⁺ and Pb²⁺ ions in paper mill wastewater samples. Three different paper mill wastewater samples were analysed by ICP-AES for their Zn²⁺, Cd²⁺ and Pb 2+components. Table-1 illustrates the metal content of the pulp and paper mill wastewater (effluent) sample. It can be gleaned from the table that significant amount of Pb²⁺ and Zn²⁺ was present in all three wastewater samples while Cd²⁺ was present at very low concentration.

Table 1: Metals content of pulp and paper mill effluents

Binding of MPL powder with Zn²⁺ Cd²⁺ and Pb²⁺ ions

present in paper mill wastewater samples:

Previous experiments have identified the optimum pH values for binding of MPL powder to Zn²⁺ Cd²⁺ and Pb²⁺ ions in artificially contaminated water samples hence the same optimum values were employed for each binding experiment in this study.

It can be seen from the table that binding capacity of the MPL powder towards Pb²⁺ in paper mill wastewater samples was found to be 29.71%(average). The result obtained is consistent with the literature (5) result obtained by Pili (32.30%) when MPL powder was mixed with the mixture of Zn²⁺ Cd²⁺ and Pb²⁺ in artificially contaminated water samples.

The sample observation has been noted in the case of binding of MPL powder with Zn²⁺ ions. Avearged of 26.3% was achieved of the binding of MPL powder towards Zn²⁺ ions present in all the sites. Ambignous result was obtained with the Cd²⁺ ions in all the three sites (Table 2) in which its concentration was found to be below the detection limit of 0.1ppm.

Table 2: Amount of Zn Pb and Cd ions bound to MPL

Binding competition between Pb²⁺ and Zn²⁺ ions :

Results shown in Table 1 indicate that both at Ukai-Songarh and Padmji, Pune wastewater samples contain equimass amounts of Pb²⁺and Zn²⁺ i.e. about 1mg metal /1mL of sample and that it was Pb²⁺ which binds most to MPL powder than Zn²⁺ ions in these samples . This observation is in contrast to what has been reported, that is in the case of artificially prepared wastewater samples. The binding for equimass amounts of metals to MPL powder must follow this order Zn²⁺>Cd²⁺>Pb²⁺. Figure 1-illustrates that in natural wastewater system it does not follow the trend but rather both metals Zn²⁺ and Pb²⁺ prefer to bind to MPL powder in almost same concentrations. This could be attributed to the stronger affinity of Pb²⁺ to the MPL powder in the presence of the other competing ions. This is due to the higher relative ion exchange selectivity coefficient of Pb²⁺ than of Zn²⁺ , thus providing stronger ionic interaction with the sulphate groups of the MPL powder (Ronquillo and Gabarai-uana, 1989; Bohumil, 1990).The results obtained from the experiments demonstrate that MPL powder is a potentially effective extractive agent for the remediation of heavy metals such as Pb²⁺ and Zn²⁺ ions in paper mill effluent samples.

Figure 1: Comparison of % bound Pb²⁺ and Zn²⁺ ions on MPL power

References

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