MATERIALS AND METHODS

3.1 Materials
The adsorbent used was the Mapecon( TM) activated carbon in powdered form. It is of technical grade (mesh 50 - ) and was solicited from the Mapecon Plant in Alaminos, Laguna. For the separation of AC from the sample, Whatman™ no.1 filters were used.

3.2 Equipment
For pH measurements in the laboratory, the pH/mV/Temperature meter and the pH 600 pen type meter were used. Oven and top loading balance (Fig. 3.1) were used in the drying and weighing of AC, respectively. Dessicator was used in cooling and storing AC. For the batch treatments, the equipment used was the Gerhardt RO™ Rotary Shaker (Fig. 3.2). Merck- SQ™ Spectrophotometer (Fig. 3.3) was used in the color and turbidity analyses. The reflux apparatus (Fig. 3.4) was used in the COD tests.
















Fig. 3.1 Top Loading Balance

















Fig. 3.2 Gerhardt RO™ Rotary Shaker

Fig. 3.3 Merck- SQ™ Spectrophotometer

Fig. 3.4 Reflux apparatus


3.3 Methods

3.3.1 Sample Collection and Preservation

Water samples were collected from a part of Pasig River System near the P. Sanchez Bridge in Mandaluyong City.

The samples were placed in opaque plastic containers. Before filling, the plastic containers were rinsed twice with the water collected. Significant amounts of suspended matter were separated by decantation, or by cloth that acted as filter.

The samples will be worthless if the physical, chemical, and biological integrity of the samples are not maintained during the interim periods between sample collection and sample analysis. Considerable research on the problem of sample preservation has failed to perfect a universal treatment or method or to formulate a set of fixed rules applicable to samples of all types.
Since delay before analysis is unavoidable, the samples were stored immediately at low temperature (4C) after collection.

3.3.2 Characterization of the Pasig River Water Samples

The pH, turbidity, color, chloride content, and COD of the samples were measured. Turbidity was measured using the nephelometric method, while the spectrophotometric method was used in the color analysis. The Argentometric method was used in the chloride determination. The open reflux method was used in all COD tests. The procedure is outlined in Appendix C.
3.3.3 Pretreatment and Characterization of Activated Carbon

a. Drying of AC
The AC was pretreated before every test. It was subjected in an oven at 110 C for 3 hours to remove the inherent moisture from its surface. Then, the dried AC was kept in a dessicator for cooling and storage.

b. Determination of Physico–Chemical Characteristics of the AC
The obtained AC was in powdered form, labeled as technical grade, mesh size of 50 pass, and iodine number of 968 mg/g. Thus, its other properties were determined experimentally. The iodine number of the AC was also empirically validated.

i. Moisture Content
The determination of moisture content was followed from ASTM standards of 1975-D 2867. 5 g of AC was heated in an electric oven at 150  C for 3 hours. Heating was continued until the weight of the sample becomes constant. The moisture content was computed by multiplying by 100 the quotient between weight lost and initial weight.

ii. Bulk Density
The bulk density is also known as apparent density. It is required by engineers to know the volume of containers that will store AC. Bulk density is affected by the raw material used and the degree of activation.
The standard procedure was followed from Beg and Usmani (1985) as cited from Encyclopedia of Industrial and Chemical Analysis. 5.5 g of AC were placed in a pre-weighed 10-mL graduated cylinder. The cylinder was tapped slightly to give the closest possible packing. Then, the volume occupied by the carbon and the added weight in the cylinder were determined.
The bulk density was computed as grams C per mL volume occupied in the graduated cylinder.

vi. Iodine Number
Iodine no. indicates the ability of particular carbon to adsorb small molecules like nitrates and other organic substances. This represents the number of mg iodine per gram of AC at a specified equilibrium concentration.
The procedure for the determination of iodine no. was based from Culp and Culp Method of 1971 outlined in Appendix D.


3.3.4 Equilibrium Contact Time Determination
The contact time determination was performed as a preliminary experiment. The initial COD concentration of the solution was determined and the samples were contacted with fixed weights of carbon for 0.5, 1, 2, 3 , 4, and 5-hour period. For this purpose, 100 mg AC was contacted with 100 mL of test solution. The samples were agitated using the rotary shaker at 155 rpm. The contact time was determined in order to know the time in which concentration equilibrium occurs. The residual CODs were determined. Statistical analysis was used to determine if there was no significant change in the residual COD.
There were two trials and the pHs were recorded.

3.3.5 Determination of Optimum pH for Maximum Adsorption

The effect of pH on the adsorption was investigated. The initial COD concentration of the solution was determined without altering its pH. This served as the control and the pH was recorded. This 100-ml control sample was contacted with 200 mg of AC at the chosen contact time. The sample was agitated using the rotary shaker at 155 rpm.
Four (4) other 100-ml test solutions were contacted at the chosen contact time with 200 mg AC at pHs higher or lower than the pH of the control sample. There were two trials and the pH was adjusted without diluting the test solutions using NaOH pellets and concentrated H2SO4. The final pHs were recorded to determine the change in pH.