¹Department of Chemistry, Panimalar Institute of Technology, Chennai, Tamil Nadu, India.

²Post Graduate& Research Department of Chemistry, Government Arts College, Ariyalur, Tamil Nadu, India.

Corresponding author email: vasanthchem84@gmail.com

Article Publishing History

INTRODUCTION

Industries such as electroplating, pickling, galvanizing, leather, metal finishing and processing, chemical etc, are also some other sources.The metal ions are highly toxic due to their bioaccumulation tendency and required affinity for the sulphydryl (-SH) groups of enzymes / proteins, thus preventing the enzymatic activity and / or disrupting the cellular structures (Bayader et al. 2018). Generally, heavy metals reason for irritation,nerve tissue damages, cardiac strain, heart diseases, disturbed metabolism, kidney malfunction, hyper-tension, ruin of central nervous and renal systems, brain damage and cancer.

Therefore, an economical way to achieve this without losing creativity and maintaining strict reset limits has become a challenge to human ingenuity and duty(Fergusson 1990; Söderholm et al. 2019).This has led to the continued refinement of existing treatment techniques and the recognition and development of promising emergent technologies like adsorption(Benjamin and Victoria 2020; Mofijur et al. 2021).

The removal of metallic ions  using an economic approach still  remains: as a great trouble even as some of successive structures have industrialized with adsorption strategies recently.. Activated carbon (AC) adsorption has advantages over traditional water treatment and reuse methods in terms of initial investment, simplicity of design, ease of operation and freedom of toxic substances.(Van 1983; Rahim et al. 2021). Commercial AC(CAC) in powder and granular forms have the most common adsorbent and broadlywas used but are expensive. This has contributed to the search for inexpensive adsorbents other than CAC.

References are made to the cultivation and use of beneficial adsorbents such as chitin and chitosan, silica, wood, peat, natural clay, bagasse heartwood, dyed cellulosic material, apple waste, waste AC, GAC models, fibers and polymers/resins. it’s possible. absorbent. However, most effective and  completely constrained quantity of statistics is to be had on using chemically prepared activated carbons (CPACs) from agricultural wastes, by product of organic material (Poots et al. 1976; Filippi and Krukonis 1980; McKay et al. 1980; McKay et al. 1982;Poots et al. 1986; McKay and Bino1987; Pollard 1992; Maranon and Sastree 1992; Shukla et al. 1992; El-Geundi 1993; McKay 1998; Annesini and Monticelli 2000; Sivakumaraet al. 2020).

Fixed bed/column processes are commonly used for pollution control methods such as ion adsorption through ion exchange beds or carbon adsorption beds. Several models have been introduced into the industry to study data and predict outcomes for different adsorption schemes.(Tien1994; Subin Parkand Junghyun 2016). Although these models based on important mass transfer mechanisms with external films, pores and bottom diffusion have been proposed, solutions of some partial differential equations involving solids and dynamic parameters are required(Löhner et al. 2021).

Shortcut models based on pilot plant testing methodremain used mostly for confirmationrelatively than information collection, money and saving time. The bed depth facility time (BDST) model andmass transfer zone [MTZ] model (Alan 1952; WalkerL andWeatherley 1997).Adsorber performance provides simple tactics and quick predictions. The BDST model has been successfully used to describe the dye adsorption of the column.

The purpose of this present study  is  to  analyse the capacity of CPACs such as SC and SDC to eliminate metal (Cu²⁺, Pb²⁺Cr³⁺ and Zn²⁺) ions from aqueous solution, by means of the column technique. CPAC was chosen because of its low cost due to the high volume of carbonaceous agricultural waste/by-products and its ease of carbonation. BDST model used to predict the performance of metal ion adsorption columns (Mamdouh 2006). The performance of column charged with granular CAC and CR [Tulsion CXO – 9(H)] was also studied and related(Vithanage et al. 2015; Afroza et al. 2020; Löhner et al. 2021).

In the fixed bed depth service time model, the basic principle of the strategy is to predict the effectiveness of the adsorbent material with which it can withstand the removal of a certain number of contaminants from the solution before regeneration is required (Mohamed et al. 2020).Required period of time is called the service time(t) of the bed. Hutchins projected a simple approach to fixed bed absorbers to relate the service time with the process variable quantity like, initial concentration, flow rate and adsorption capacity, by equation (1) (Arunachalam et al 2021).

t = [(N_oZ) / C_oV] – {(1/k_aC_o)  ln [(C_o/C_b)-1]}                   …        (1)

where, C_o = initial concentration of metal (mg dm^-3) (Zümriye Aksu, JülideYener 2001)

C_b = break through adsorbate concentration (mg dm^-3)

k_a = BDST adsorption rate constant (dm³ mg^-1 min^-1)

V  = velocity (cm min^-1)

Z  = bed height (cm)

The theoreticdeepness of adsorbent (AC) adequate to avoid the adsorbate concentration from beyondC_b at t = 0, termed the bed depth (Z_o, in cm) can be attained, when the service time is zero (t = 0) and given by equation (2):

Z_o = (V/ k_a N_o) ln [(C_o/C_b)-1]                          …        (2)

By determining the service time t for the formation depth Z from the experimental data, we can estimate No and ka from the slope of the graph and the values ​​of the intersection (at t = 0), respectively. Graph of the critical formation depth equation.Reciprocalvalue of sloperemains the rate at which the adsorbent bed is consumed, and increasing this particular value by the adsorbent’s outward bulk thickness gives adsorbent utilized rate to continuous discharge waste water of acceptable quality (Elwakeel et al. 2020). BDST is written as simplified method as follows:

t = AZ + M                                         …        (3)

where, slope,

A = (N_o / C_oV)                                                …        (4)

and intercept,

M = (1/k_aC_o) ln [(C_o/C_b)-1]                  …                    (5)

The value of straight line presented is used to explain the working of the bed, if there is initial concentration C_o,1, to a new value C_o,₂, Hutchins  projected that new slope A₂ and new intercept M₂ can give by eqns.(6) and (7), similarly.

A₂ = A₁ (C_o,1/ C_o,2)                                                      …                                            (6)

M₂ = M₁ (C_o,1/ C_o,2) ln {[C_o,2/ C_o,b)-1] / [C_o,1/C_o,b)-1]}                                    …        (7)

(McKay et al. 1998)detailed that, When the calculated data is important for changing the permeate volume flow rate in a similar adsorption system, the new slope (A2) through the unaltered segment (M2 ; M2 = M1) can be written as:

A₂ = A₁ (Q₁/ Q₂) = A₁ (V₁/ V₂)                                   …        (8)

Apart from BDST model, MTZ model also predicts the design parameters similar to the BDST model.

MATERIAL AND METHODS

The activated carbon prepared by Sol gel method(Nurul et al. 2021). Chromium (Cr), Lead (Pb), Zinc (Zn), Copper (Cu) and were determined by spectrometric method using Atomic Absorption Spectrometer – Model: PerkinElmer-Analyst -400.  The obtained results were formulated, estimated and mentioned according to the standards prescribed below ‘Indian standard drinking water specification IS 10500: 1992’ of Bureau of Indian Standards [BIS].

For the fixed bed experiments, the groundwater from the column is collected at regular intervals of time (30 – 45 min.) and the metal ions were estimated spectrometric method using Atomic Absorption Spectrometer – Model: PerkinElmer-Analyst -400(Allen and Minear 1982;Rao and Ramakrishna 1982; Jefferyet al. 1991; Lahrich et al 2019).

RESULTS AND DISCUSSION

Effect of initial concentration: The specific concentration of metal ions in the raw water is an important parameter and major determinant, but a given adsorbent capacity only absorbs a certain amount of metal ions. So, for the more concentrated solution of an incoming, the small amount of adsorbent can purify. Many experiments have been done to study the effect of changing the initial concentration on the rate of metal ion removal from solution. An increase in initial metal ion concentration increases the slope of intercept curve, decreasing the volume of influent treated earlier the adsorbent renewal and also results in an early breakthrough and exhaustion of the bed/column(Talat et al. 2018; Abdullah et al. 2019; Bounaaset al. 2021).

Activated Carbon Characterization : The activated carbon was prepared from three different plants of stems used (Neem, Mango and palm tree) (bulkdensity, porosity, porevolume, ash content,Average particlesize, iodine number etc,) and characterized by SEM (Bounaaset al. 2021). ThedataofthepreparedsamplesareshowninFig1.

Table 1. Characteristics of Activated carbon prepared from Mixed Plants

Parameter	Observed Value	Standard Value
Bulk Density	0.521gm/cm3	1.285 gm/cm3
Porosity	1.253 cm3g-1	1.365 cm3g-1
Iodine Number	1022 mgs/gm	576.86 mgs/gm
Average particle size	0.76 mm	0.81 mm
Ash content	8mg/g	10.65 mg/g

Figure 1: SEM images of Activated carbon prepared from three different stems of plants

Table 2. Concentration of heavy metal in ground water samplesbefore adsorption.

S.No	Heavy metals	BIS (IS 10500: 1991)	R-1	R-2	R-3	R-4	R-5	R-6	R-7	R-8	R-9	R-10
1.	Chromium	0.05	0.528	0.834	0.538	0.24	0.451	1.06	0.31	0.201	0.507	0.211
2.	Lead	0.01	0.324	0.156	0.232	0.258	0.125	0.26	0.526	0.291	0.123	0.199
3.	Zinc	5 – 15	7.32	9.24	6.45	12.16	11.84	8.16	8.28	4.95	6.9	4.06
4.	Copper	0.05 – 1.5	4.45	7.94	5.58	3.42	6.84	5.88	4.56	3.28	6.24	4.48

Table 3. Concentration of heavy metal in ground water samples after adsorption.

S.No	Heavy metals	BIS (IS 10500: 1991)	R-1	R-2	R-3	R-4	R-5	R-6	R-7	R-8	R-9	R-10
1.	Chromium	0.05	0.201	0.507	0.211	0.092	0.124	0.384	0.086	0.174	0.18	0.082
2.	Lead	0.01	0.291	0.123	0.199	0.225	0.092	0.235	0.493	0.258	0.09	0.166
3.	Zinc	5 – 15	4.95	6.9	4.06	9.79	8.84	5.78	5.89	2.56	4.51	1.67
4.	Copper	0.05 – 1.5	3.28	6.77	4.41	2.22	5.63	4.71	3.4	2.11	5.6	3.24

Table 4. The percentageremoval of Chromium, Lead, Zinc and Copper with respect to time using
CPACDosage = 3 g/100 mL, pH = 4, Temp = 300 K

Time in mins	% Removal of heavy metal with respect to dosage
	Cr	Pb	Zn	Cu
15	55.85	51.53	59.56	56.45
30	59.42	52.53	62.53	57.86
90	67.54	61.23	69.85	63.85
120	71.23	64.78	71.53	65.42

Figure 2: The percentage removal of Heavy metal with respect to contact time

Table 5. The percentage removal of Chromium, Lead, Zinc and Copper with respect to dosage
of Activated carbonContact time 30 minutes, pH = 4, Temp = 300 K

Dosage amount	% Removal of heavy metal
	Cr	Pb	Zn	Cu
3g	55.62	50.53	58.56	55.53
5g	58.63	51.23	61.42	56.53
7g	60.53	53.23	63.54	56.12
9g	63.17	57.53	66.51	60.54

Figure 3: The percentage removal of Heavy metal with respectto dosage of adsorbent

Table 6.The percentage removal of Chromium, Lead, Zinc and Copper with respect to pH using
CPACDosage = 3 g/100 mL, Contact time 30 minutes, Temp = 300 K

pH	% Removal of heavy metal with respect to pH
	Cr	Pb	Zn	Cu
1	51.53	49.53	48.53	43.53
2	54.56	53.23	51.53	48.46
3	60.53	55.45	53.59	56.53
4	65.53	57.86	59.53	62.53
5	60.27	42.53	50.42	52.42
6	40.23	37.89	35.53	42.53
7	35.23	32.21	29.53	36.35
8	30.26	27.53	24.53	27.53
9	25.63	22.53	22.53	21.53

Figure 4: The percentage removal of Heavy metal with respect to pH

 

Table 7. The removal percentage of Chromium, Lead, Zinc and Copper with respect to
Temperature using CPACdosage = 3 g/100 mL, Contact time 30 minutes, pH4

Temperature(0 C)	% removal of heavy metal with Temperature
	Cr	Pb	Zn	Cu
30	55.53	54.53	49.53	46.53
40	57.86	56.53	50.23	48.53
50	60.19	58.53	50.93	50.53
60	62.52	60.53	51.63	52.53
70	64.85	62.53	52.33	54.53
80	67.18	64.53	53.03	56.53

Figure 5: The percentage removal of Heavy metal with respect to temperature Heavy metal

Consequence of contact time on removal of heavy metals: The result of contact time on the exclusion of Activated carbon was evaluated for various concentrations (3 to 9 g/L), at regular time interval 15 to 80 minutes showsaincrease in metal concentration removal with increase in time and concentration of Activated carbon(Marrakchi et al. 2020).The increase in thickness of activated carbon increases the number of active sites on the surface get increases, which involved in removal of heavy metal ion in groundwater samples. It is explained that the part of degradation this metal concentration (Pb, Cr, Zn and Cu) progressively increased 3 to 9 g/L, afterward there is no removal of metal concentration.(Fig 2 & 5).

This indicates that the fluid to adsorbent mass transfer rate of the metal ion increases with the increase in initial concentration (C_o).  This is expected, since the concentration gradient across the film surrounding the adsorbent particle will be higher at the higher concentrations of metal ions (Felebueguet al. 2006; Dev et al. 2020). Increasing the concentration of metal ions entering the continuous stream decreases the output. This is due to high initial concentration (C_o) soaking the adsorbent rapidly, thusreducing the break through time(Awan et al. 2021).

Consequence of catalyst dosage on removal of Pb, Cr, Zn and Cu: The experiments done withchanging the amount of dosage from 3 to 9 g/L for groundwater samples.  The solutions kept under sunlight illumination for 15 to 80 minutes. As a result,shown remarkably greater in removal of heavy metal concentration from 40 mg/L dosage.It is well understood that the removal heavy metal concentration from groundwater activity increase with the increase in the dosage of Activated carbon(Fig 2 to 5)(Sujatha et al. 2021).

% of removal heavy metal concentration = (Absorbance at initial –Absorbance at final)/Absorbance at initial) X 100

The percentage removal of removal heavy metals was calculated using above formula and experimental data obtained from different experiment.

Effect of pH and Temperature on removal of heavy metals: The removal of heavy metal is high at pH 4, after pH 4 the percentage removal of heavy metal decrease, this is due to increase repulsion between adsorbent and heavy metal ions(Almomani et al. 2020). The removal percentage of heavy metal increase with increase time up to 80 minutes and further rising temperature decrease the percentage removal of heavy metal, this is due to desorption takes place above 80⁰C(Jayanthi et al. 2021).

CONCLUSION

The findings of the present study  show that  the amount of wastewater treated before the initial breakthrough was directly proportional to the capacity of the adsorption tower and increased as the contact time increased. The effect of contact time on the amount of metal ions adsorbed by other metals also increased. Activated carbon was effectivelyproduced by sol-gel method and it was characterized by SEM.  The produced Activated carbon was utilized for removal Pb, Cr, Zn and Cu metals from groundwater samples.

It is clear that the part of exclusion of heavy metals of groundwater gradually improved from 50 to 80 percent. The percentage removal of heavy metals graduallyimproved with contact time up to 120 minutes. This environmentallygood Activated carbon material used for removal of heavy metal such as Pb, Cr, Zn, Cu. It is concluded that activated carbon prepared from mixed plants more efficient and very cheap than other types of adsorbents. Also, this study is very useful for researcher and public to get an idea about the removal of heavy metals ion in groundwater.

ACKNOWLEDGEMENTS

The laboratory facilities for this study were provided by the Panimalar Institute of Technology, Tamil Nadu, India.

Conflict of Interests: Authors declare no conflict of interests to disclose.

Data Availability Statement: The database generated and/or analysed during in the current study are not publicly available due to privacy and confidentiality agreements as well as other restriction but are available from the corresponding author on responsible request.

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