Heavy Metals Removal by Hydroxide Precipitation and Coagulation-Flocculation Methods from Aqueous Solutions

Abstract

The hydroxide precipitation and coagulation-flocculation methods were used to treat wastewater containing lead, zinc, copper, and iron. The concentrations of heavy metals in the synthetic wastewater range from 1 to 14 mg/L for lead, 5 to 90 mg/L for zinc, 3 to 90 mg/L for copper and 5 to 45 mg/L for iron. Individual Zn(II) and Cu(II) with concentrations below 90 mg/L and Fe(III) with concentrations below 45 mg/L were removed up to 99% by the precipitation method in the pH range of 8.7 to 9.6, 8.1 to 11.1, and 6.2 to 7.1, respectively. Though the highest percent removal of Pb(II) by hydroxide precipitation alone was approximately 98%, the final dissolved concentrations did not fulfill the Standard A discharge limit required by the regulations, thus further treatment by the coagulation-flocculation process was performed. Aluminum sulphate (alum), polyaluminum chloride (PACl) and magnesium chloride (MgCl2) have been used as coagulants together with Koaret PA 3230 as coagulant aid to determine the effectiveness of the coagulation method for the removal of individual heavy metals in the wastewater. The effects of parameters such as pH, type, and dosage of coagulant on the percentage of metal removal, and the amount of coagulant aid on the flocs settling time were investigated. The jar test showed that up to 99% removal of Pb(II) was attained by the addition of 1,200 mg/L of alum, 150 mg/L of PACl, and 2,000 mg/L of MgCl2 in a pH range of 6.5 to 7.8, 8.1 to 8.9, and 9.7 to 10.9, respectively.

Equilibrium and kinetics studies for the adsorption of Ni2+ and Fe3+ ions from aqueous solution by graphene oxide

“…Therefore, it becomes necessary to remove heavy metals from wastewaters before they are released into the environment. Several techniques have been used to remove heavy metals from industrial wastewater including chemical precipitation 1 , coagulation 2 , ion exchange 3 , membrane fi ltration 4 , reverse osmosis 5 , electrolytic processes 6 and adsorption 7 . Among these methods, adsorption has been proved to be an effi cient and economical technique.…”

Transport of Zn (II) by TDDA-Polypropylene Supported Liquid Membranes and Recovery from Waste Discharge Liquor of Galvanizing Plant of Zn (II)

“…Traditional techniques of recovery for metal ions, such as adsorption [7,8], solvent extraction [9][10][11][12], precipitation [13], and ion exchange [14]. have normally low efficiency, require high capital and operating cost, and produce secondary pollution complications [15].…”

Synthesis of a novolac‐based 3‐aminopropylsiloxane resin and its application for the removal of Cu2+, Cr3+, and Ni2+ from electroplating wastewater

“…Therefore, the removal of heavy metal ions from industrial effluents is imperative, prior to disposal in nature. There are a variety of techniques that can be used for removing heavy metal ions including adsorption, chemical precipitation, ion exchange, and membrane separation . Ion exchange technique is one of the common methods that are preferably used for treatment of aqueous wastes because of its selectivity, simplicity, using of nontoxic materials and recyclability.…”