SOURCE:

Faculty: Physical Sciences
Department: Pure And Industrial Chemistry

CONTRIBUTORS:

Iloamaeke I. MaryJane
Onuegbu T. U.
Eboatu A. N.

ABSTRACT:

Natural coagulants, Mercenaria mercenaria (MM), Archachatina marginata (AM), Tympanotonos fuscatus (TF) in their unmodified and modified forms (MMM, MAM and MTF) were used to treat paint industrial effluent by coagulation- flocculation (CF) process. Proximate and Physicochemical analyses were carried out on both unmodified and modified coagulants using standard methods. Surface morphology, crystallinity, elemental composition and functional groups of unmodified and modified coagulants were determined using standard instruments namely SEM, XRD, XRF and FTIR. Response Surface methodology by Box Behnken design was used in coagulation-flocculation proccess. The efficiency of the Coagulation-flocculation process was quantified in terms of colour removal and the result optimized by Box Behnken design. Kinetics of the coagulation-flocculation was also determined. The values of bulk and tapped densities, Carr’s index, porosity, Hausner ratio, and surface area analyses indicated that both modified and unmodified coagulants have good flow rate which will enhance settling of particles during sedimentation. Proximate composition of these six coagulants showed that both modified and unmodified coagulants have highest carbohydrate content in this order: modified MM (64.666%)> modified AM (63.389)>modified TF (58.899%)>TF (54.017%)>AM (52.756%)>MM (52.171%). Physicochemical analyses before treatment showed that the paint effluent was highly polluted based on; alkalinity (3900 mg/L), total hardness (720 mg/L), chloride (2770 mg/L), chemical oxygen demand (720 mg/L), biological oxygen demand (534mg/L) and turbidity (834mg/L). However, after treatment with both modified and unmodified coagulants, the values of these properties decreased appreciably with most of them coming within the standards for effluent disposal. The results of the coagulation-flocculation experiment were well interpreted by second order polynomial regression model from BBD design with coefficient of determination R2 close to unity. Analysis of variance (ANOVA) of the quadratic model demonstrated a probability value of < 0.0001 implying that the model is highly significant. 3D surface plots revealed that interactive effects of dosage, pH, and settling time had significant impact on the colour removal efficiency. Coagulation-flocculation process was optimized using desirability function in all the coagulants. MM, AM and TF coagulant have optimal colour removal efficiency of 75.94% at dosage of 100 mg/L, pH 2 and time 20 mins, 77.96% at dosage of 500mg/L, pH 2 and time 20 mins, 83.83% at dosage of 300 mg/L, pH 2 and time 30 mins respectively. For the modified coagulants: MMM, MAM and MTF have optimal colour removal efficiency of 82.39% at the dosage of 364.21mg/L, pH 6 and time 14.15 mins, 82.79% at dosage of 399.72 mg/L, pH 2.181 and time 29.92 mins, 91.45% at dosage of 500 mg/L, pH 6 and time 20 mins respectively. XRF result indicated that these coagulants contained highest % calcium:MAM(99.509%)>AM(99.451%)>MTF(99.162%)>MM(99.135%)>TF(99.067%)>MMM(92.762%) . XRD result showed that all the coagulants have amorphous structure except MTF which has crystalline structure. SEM and FTIR analyses before and after treatment confirmed that these coagulants removed impurities from the effluent. Second order reaction kinetic fitted better in all the coagulants. The best coagulant is rated in this order: MTF>MAM>MMM>TF>AM>MM. Finally, the results showed that all the coagulants used in this study can serve as an alternative coagulant in the treatment of paint effluent.