Removal of Heavy Metals from Pharmaceutical Industrial Wastewater Effluent by Combination of Adsorption and Chemical Precipitation Methods

Abstract

The removal of heavy metals from our environment especially industrial effluents is now shifting from the use of conventional adsorbents to the use of chemical precipitation. The presence of heavy metals in the environment is a major concern because of their toxicity, bioaccumulating tendency, and threat to human life and the environment. The main objective of this research is to study the effectiveness of the combination of hydrogen peroxide and activated bentonite clay in the removal of heavy metal ions from pharmaceutical industrial effluent. About 13.790 mg/l of Fe, 1.650 mg/l of Zn and 2.000 mg/l of Ni were detected in the digested sample and batch removal of heavy metals such as Fe, Zn and Ni from industrial wastewater effluent under different experimental conditions using hydrogen peroxide as precipitating agent in combination with activated bentonite clay as adsorbent. Appreciable differences in the level of heavy metals concentration were observed based on pH effect. The result shows higher effectiveness relatives to other treatments formulated for the effluent treatment such as Alum precipitation effect, effect of hydrogen peroxide concentration dose, contact time effect and temperature effect. Removal of heavy metals in effluent was optimum at pH 10 for zinc (Zn) and nickel (Ni) and at pH 8 for iron (Fe), at temperature of 50°C, 0.75% hydrogen peroxide concentration dose and 100 mins holding time, reducing the amounts from 13.790 to 1.436 mg/l of Fe, while 1.650 to 0.127 mg/l of Zn and 2.000 to 0.115 mg/l of Ni respectively. The percentage differences in concentration for the heavy metals removal in industrial wastewater are as follows: Fe (89.58%), Zn (92.30%) and Ni (94.22%). The result showed high level of Zn and Ni generated from this pharmaceutical industry is above 1 mg/l FEPA and WHO standard but only Fe showed low level concentration compared to 20 mg/l FEPA and WHO standard in this study. This study reveals the need for enforcing adequate effluent treatment methods before their discharge to surface water to reduce their potential environmental hazards.