1.       Introduction

Contamination of water by heavy metals is a critical environmental and health concern worldwide [1]. Metals with atomic density greater than 4g/cm³ belong to heavy metals. Cu, Cd, Zn, Pb, Hg, As, Ag, Cr, Fe, and Platinum group elements are heavy metals [2]. Iron in its divalent form, Fe(II), a secondary pollutant generally found in water sources, can pose serious health hazards and environmental concerns when present in excess concentration. According to World Health Organization (WHO) guidelines, 0.3 mg/L of iron in drinking water is safe for consumption [3]. Therefore, the effective removal of Fe(II) ions from aqueous systems is of great importance [4].

Several conventional techniques, such as ion exchange, membrane filtration [5], chemical precipitation [6], and coagulation-flocculation [7], have been used for heavy metal removal. However, many of these methods are expensive, generate secondary pollutants, or require sophisticated infrastructure. In contrast, adsorption has emerged as a simple, cost-effective, and eco-friendly alternative. The use of natural bio-adsorbents, in particular, offers additional benefits such as renewability, biodegradability, and low operational cost [8-10].

In the present study, we investigated the adsorption of Fe(II) ions at different initial metal ion concentrations using two natural bio-adsorbents: Marua plant and Albizia lebbeck. A comparative analysis was carried out to evaluate their adsorption efficiency under specific experimental conditions of pH and temperature [11-13]. The results indicate that adsorption capacity increases with rising initial Fe(II) concentration until equilibrium is reached [14]. It was also finds that adsorption increases with increase in contact time [15]. Furthermore, the adsorption potential was found to be higher in leaf-based adsorbents compared to seed-based ones. Among the two tested bio-adsorbents, Albizia lebbeck demonstrated superior adsorption efficiency compared to the Marua plant under the studied conditions.

2.   MATERIALS AND METHOD

Chemicals and reagents

All chemicals used in this study were of Analytical Reagent (A.R.) or Laboratory Reagent (L.R.) grade and were used without further purification. Ferrous ion solutions of desired concentrations were prepared using FeSO₄·7H₂O with double-distilled water. The 1,10-phenanthroline reagent was used for colorimetric determination of Fe(II) ions.

Preparation of Bio-adsorbents

Leaves and seeds of Marua plant and Albizia lebbeck were collected, washed thoroughly with distilled water to remove surface impurities, and dried at room temperature. The dried materials were then ground into fine powder and sieved to obtain a uniform particle size. The prepared powders were stored in airtight containers and used as bio-adsorbents.

Batch Adsorption Experiments

Batch adsorption experiments were carried out by adding 500 mg of bio-adsorbent to 50 mL of Fe(II) solution of known concentration in separate glass bottles. The bottles were agitated in a mechanical shaker at predetermined time intervals of 60, 120, 180, 240, and 300 minutes. After shaking, the suspensions were centrifuged and filtered to separate the adsorbent from the aqueous phase.

Analytical Determination

The residual Fe(II) ion concentration in the filtrate was determined spectrophotometrically using the 1, 10-phenanthroline method. Absorbance was measured at the characteristic wavelength for Fe(II)-phenanthroline complex.

Experimental Parameters

The effect of different operational parameters on Fe(II) adsorption was studied, including:

• Initial Fe(II) ion concentration: 100, 150, 200, and 250 mg/50 mL
• Solution pH: maintained at 8.0
• Temperature: maintained at 303 KTop of Form

3.   RESULT AND DISCUSSION

MARUA PLANT

Table 1 Impact of Commencing Metal Ion Strength (Leaf of Marua Plant)

Fig. 1: Effect of Initial Metal Ion Density

Table 2: Effect of Metal Ion Amount per volume (seed of Marua Plant)

 Fig: 2 Effect of Initial Metal Ion Concentration

Albizia lebbeck

Table 3: Effect of Initial Metal Ion Potency (Leaf of Albizia lebbeck)

Fig.3: Effect of Initial Concentration of Metal Ion

Fig.4: Effect of Metal Ion Concentration

 Fig.5: Comparative Study of Adsorption

Fig: 6 Comparative study of Adsorption

CONCLUSION

Figs represent % removal of Fe (II)   versus the starting metal ion concentration. The study of the graph shows that, with an increase in metal ion concentration, the % removal of Fe (II) ion decreases.  The reason for this is that a limited number of active sites are present in the active site of the adsorbent, and after saturation, there is no adsorption at the active site. Leaf shows much better adsorption capacity than the seed. Albizia lebbeck shows better adsorption capacity than the Marua plant in particular condition (pH and Temperature).