REMOVAL OF A CHEMICAL DYE FROM WASTEWATER USING LOW COST AGRO-BASED ADSORBENTS : CONTINUOUS ADSORBERS

Natural materials that are readily available in large amounts in nature and easily accessible may be used as low cost additives. The aim of this study is to measure the susceptibility of these locally available materials, conocarpus plant, to improve the quality of wastewater discharged from textile industry. In addition to conocarpuswithout chemically treated, conocarpuschemically treated, carbonized conocarpus and activated carbon were used as adsorbents in order to make a comparison, and to test which one of the four types give the best efficiency for removing dye. The ability of adsorbents to adsorb dye was studied using continuous system; studied parameters were effect of flow rate, bed depth, and initial concentration. The experimental results showed that maximum removal efficiency of conocarpus without chemically treated was found to be 90% after 75 min at flow rate 20 l/h, pH value 3 , bed depth 5cm and initial concentration 40 mg/l. The maximum removal efficiency for conocarpuschemically treated was up to 83.75% after 15 min at flow rate 10 l/h, pH value 3, bed depth 10 cm and initial dye concentration 40 mg/l. The maximum removal efficiency for carbonized conocarpus was up to 99.67% after 15 min at flow rate 10 l/h, pH value 3, bed depth 10 cm and initial dye concentration 40 mg/l. For activated carbon the maximum removal efficiency was found to be 99.75% after 15 min at flow rate 10 l/h, pH value 3, bed depth 10cm and initial dye concentration 40 mg/l.


INTRODUCTION
The process of removing dyes and industrial wastes, is one of the major worldwide natural issues.And that textile manufacturing and dyeing is one of the processes that produce wastewater in large amounts.Wastewater-equipped textiles contain a residue treatment bath from preparation,dyeing, finishing, reduction, and other processes (Korbahti 2007).
Wastes from textile and dyeing industry cause serious environmental damage to adjacent aquatic particle because of presence of hazardous chemical dyes , dark coloring and chlorine residues (Asamudo et al., 2005 ;Senel et al., 2012).

SOURCE OF WASTEWATER
Solution was prepared by dissolving (40) mg of terasil blue dye in 1000 ml of a tap water, this concentrations of solution will be used for all experiments.The dye components (Table 1) were examined using Eds device (Type Xact , USA) .The measurements were conducted at the Central Service Laboratory -College of Education Ibn Alhaitham, University of Baghdad.

ADSORBENTS
In this study, four absorbent substances were used conocarpus-without chemically treated, carbonized conocarpus, conocarpus -after chemically treated, and activated carbon.

PHYSICAL PROPERTIES OF ADSORBENTS
Physical properties of conocarpus plant ,carbonized conocarpus and activated carbon have been measured such as solubility, specific surface area, bed porosity, bulk density, real density, pore volume and pore size.

PREPARATION OF THE ADSORBENTS
Preparation of the adsorbent materials; conocarpus -without chemically treated, conocarpus-after chemically treated and carbonized conocarpus are illustrated below.

Preparation of conocarpus-without chemically treated
Conocarpus leaves was taken from the campus of Wasit University to be used in this study.The previous studies (Hussein et al., 2016) were adopted as a working method for preparation of conocarpus.Plant leaves washed three times by using distilled water to get rid of any dust.After finishing washing, it is dried in the oven at 110 ° C for 3 hours; then grinded in a mill to a small volume of less than 500 microns.The last step of the preparation process is sieving through (150 -300) μm.

Preparation of carbonized conocarpus
The previous studies (Ramadan et al., 2005) were adopted as a working method for carbonization of conocarpus plants.The following steps illustrate the preparation of carbonized conocarpus: 1. Cutting the plant into small pieces.
2. Washing it three times with distilled water to clean it.
3. Dry it at 110 o C for three hours and repeat the drying step for other quantities until the required quantity is obtained.
4. The dried plant is grinded into small granules using grinder.
5. 1: 0.5 of the conocarpus and sodium hydroxide are mixed well.
6. Put the mixture in oven at temperature 300 oC for half an hour with continuous flipping 7. Raise the temperature to 500 o C for an hour and a half.The total time for carbonization process was two hours.
8. Wash the product in the filtration device twice with distilled water and then washed with hydrochloric acid at a concentration of 10% once to remove the effect of base solution then wash it with water once to remove acidic excitation.
9. The product is then dried in oven at 110 ° C for three hours, then grinded into small granules.

Preparation of conocarpus-chemically treated
Several experiments were conducted to pull the color of the conocarpus.The best result was obtained using the following procedure: 1. Cutting plant leaves.
2. Washed three times with distilled water to get rid of any dust.
3. Dried in the oven at 110 ° C for 3 hours.
4. Grinded in a mill to a small volume of less than 500 microns.
5. Wash the product again in the filtration device twice with distilled water.
6. Put the product in solution of hydrochloric acid at a concentration of 10% For a full day then wash it with water once to remove acidic excitation.
7. Wash the product again in the filtration device with Hydrogen peroxide then wash it with water once to remove Hydrogen peroxide excitation.
8. Dried in the oven at 110 ° C for 3 hours.9. Grinded in a mill to a small volume of less than 500 microns.

ACTIVATED CARBON
Powder activated carbon PAC (German origin) as shown in figure (7) was used as adsorbent in the experiments.PAC Specifications are shown in table (3).e. Flow meter to measure flow rate (0 -30 l/ h).

SYSTEM STRUCTURE AND EQUIPMENT REQUIREMENTS
f. Pump of maximum capacity of 50 liters / hour.
g. Gate valves are used to control the flow in the system.
h.Two sampling points were selected, first from the top of the fluidized column and the other before the feeding tank.

EXPERIMENTAL PROCEDURE
a -The adsorbent was placed in adsorption column to the required bed depth.
b-The terasil blue dye solution with the desired concentration was prepared in the cylindrical steel tank, using tap water.
c-The terasil blue dye solution was adjusted to pH 3 using NaOH or HCl.
d-The terasil dye solution was pumped into the absorption column through the flow meter at the required flow rate.
e-Samples were taken periodically; the concentration of terasil dye was measured using UV device (type IRPRESTIGE-2; Shimadzu 8000, Japan).
f-The break through curves were determined by plotting (Ce/Co) with time.The experimental conditions are shown in table (4).

EFFECT OF FLOW RATE
The effect of flow rate on the adsorption process in fluidized bed column was investigated.Breakthrough curves were obtained at different flow rates 3, 10, and 20 l/h at initial concentration 40 mg/l and bed depth 5 cm, as shown in figures ( 9), ( 10) and (11) .When the adsorbent; activated carbon , carbonized conocarpus and conocarpus -after chemically treated; were used at flow rates 10 l/h and 20 l/h, the breakthrough curves occurred rapidly with increasing flow rate because the dye had less time to contact with absorbent materials that led to the removal of less dye figures ( 9), ( 10) and (11).The breakthrough period increased significantly with a decrease in flow.Absorption becomes smaller with increased hydraulic load due to reduced contact time between dye and absorbent materials.With high flow rate, Ce /Co increase rapidly.Compared to a fixed bed column it did not have this speed because the surface area of the absorbent material is limited in the fixed bed due to the dead zone that appear between the particles.These results are consistent with the results obtained by Wang et al., (1997).
At low flow rate 3 l/h the dispersion velocity of the absorbent materials and dye is low, so their kinetic energy becomes less and the attractiveness of the dye molecules decreases.Therefore, the adsorption process is less efficient when discharge is very low.
When the concarpus-without chemically treated was used as adsorbent, a quick absorption of the terasil blue dye occurred as the flow rate decrease (figure 12).The breakthrough curves have reached a breakthrough state with remarkable speed at low flow rate.This is because the low flow rate the greater contact time for the solution with sorbent , and the more time lead to the plant's susceptibility to give the green color, because of the plant did not undergo to carbonization process or chemically treated.At flow rate 10 l/h, it is shown that activated carbon is more effective in the process of adsorption where the maximum efficiency of removal 99.44%, followed by carbonized conocarpus where the maximum efficiency of removal 95.45%.For the conocarpus -after chemically treated the maximum efficiency of removal was 80.72 % and for the conocarpus -without chemically treated the maximum efficiency of removal was 75 %.
At flow rate 20 l/h, it is shown that activated carbon is more effective in the process of adsorption where the maximum efficiency of removal 99.4%, followed by carbonized conocarpus where the maximum efficiency of removal 95.25%, for the conocarpus -without chemically treated the maximum efficiency of removal was 90%, and for the conocarpus -after chemically treated the maximum efficiency of removal was 75.77%.

EFFECT OF BED DEPTH
From figures ( 13) , ( 14) and ( 15) the slope of the breakthrough curve at a bed depth of 10 cm is lower than that of 7.5 cm and 5 cm.When the bed depth increases, the removal efficiency increases.In the higher depth, more terasil dye pull out from the solution compared to the lower depth.It also shown that the curved slope of breakthrough curves less in fluidized bed compared to a fixed bed because of the presence of dead zone that appear in the hard bed.These conclusions are similar to those obtained by Han et al, (   By comparing among the adsorbents, at initial concentration 40 mg/L, it is shown that activated carbon is more effective in the process of adsorption where the maximum efficiency of removal 99.44%, followed by carbonized conocarpus where the maximum efficiency of removal 95.45%.While the maximum removal of efficiency of conocarpus -after chemically treated was 80.72%, and for the conocarpus the maximum efficiency of removal was 75%.
At initial concentration of terasil dye 70 mg / L, it is shown that activated carbon is more effective in the process of adsorption where the maximum efficiency of removal 94.14%, followed by carbonized conocarpus plant where the maximum efficiency of removal 93%.While the maximum removal of efficiency of conocarpus -after chemically treated was 71.42%, and for the conocarpus plant the maximum efficiency of removal was 21.4%.
At initial concentration of terasil dye of 140 mg / L, it is shown that activated carbon is more effective in the process of adsorption where the maximum efficiency of removal 89.28 %, followed by carbonizedconocarpus where the maximum efficiency of removal 82.14 %.While the maximum removal of efficiency of conocarpus -after chemically treated was 65%, and for the conocarpus plant the maximum efficiency of removal was 13%.Copyright  2018 Al-Qadisiyah Journal For Enginnering Science.All rights reserved.It is found that the breakthrough curves depend on the physiochemical properties of the absorbent material such as the composition of the feeding solution, the operation column, the initial concentration, bed depth, and flow rate.
2. It is observed that when the bed depth of conocarpus -chemically treated ,carbonized conocarpus plant and activated carbon increased, the adsorption process becomes more efficient, Either in case of the use of conocarpus -without chemically treated, when the depth of bed increases the adsorption process decrease 3. when use conocarpus -chemically treated, carbonized conocarpus plant and activated carbon , it is shown that the time needed to reach the breakpoint decreases with the flow rate increasing, but in

Figures ( 1 )
Figures(1),(2) and(3) show the outer surface and surface morphology of the conocarpus , carbonized conocarpus and activated carbon particles respectively using scanning electron microscope SEM (Type AIS2300, USA).The measurements were conducted at the Central Service Laboratory -College of Education Ibn Alhaitham, University of Baghdad.

Figure 5 .
Figure 5. conocarpus-without chemically treated and carbonized conocarpus, materials used as adsorbents in the present study.
a. 80-liter cylindrical steel tank for preparation of terasil blue dye solution.JOURNAL OF AL-QADISIYAH FOR ENGINEERING SCIENCE Vol.11, No. 2 ISSN: 1998-4456 Page 237 Copyright  2018 Al-Qadisiyah Journal For Enginnering Science.All rights reserved.b. 30 liter container for liquid waste collection.c. column made of glass material with an internal diameter of 50 mm and height of 1000.d.PVC flanges and various sizes of hoses and pipes joined together by different fittings.

Figure 12 .
Figure 12.Breakthrough curves for terasil dye adsorption onto conocarpus-without chemically treated at different flow rates, 20 , and pH 3

Figures ( 17
Figures (17)  to (20) show the effect of initial concentration of dye on the shape of breakthrough curves.Three initial concentrations 40, 70 and 140 mg/L were adopted in the fluidized bed column experiments.Whenever the initial concentration increases, the more likely the penetration curves are obtained.At the highest initial concentration of terasil blue dye, the absorbent bed is exhausted in the shortest time and this leads to early breakthrough.This has a decrease in the stop point with increased concentration of the dye where the link sites are quickly saturated in the column.The curved slope of breakthrough curves less in fluidized bed compared to a fixed bed because of the presence of dead zone in fixed bed.

Table 1 .
the components in terasil blue dye
The measurements were conducted at Ministry of Oil / Petroleum Research & Development Center,

Table 3 .
Specifications of activated carbon.

Table 4 .
Experimental conditions of the experiments used in the present study.
2. RESULTS AND DISCUSSIONCopyright  2018 Al-Qadisiyah Journal For Enginnering Science.All rights reserved.