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Removal of Lead from Wastewater

by

technolab el-bahaa group

general.dr

bahaa badr

chemical consultant

Lead is often found in wastewater from printed circuit board factories, electronics assembly plants, battery recycling plants and landfill leachate.

In the printed circuit factory, solder plating and etching operations is the lead source.

In the electronics assembly operations, the source is solder flux cleaning.

In battery breaking, the lead is found in the sulfuric acid from the battery.

In landfill leachate, it can be found as an organo metallic like tetra ethyl lead.

Since lead hydroxide is moderately soluble, it cannot be treated by pH adjustment to regulated concentrations.

It is often treated by precipitating lead sulfide or phosphate, using a two step process.

It can also be treated by reduction or by ion exchange.

When using ion exchange, it is difficult to remove the lead from the resin by regeneration requireing the disposal of the spent resin.

Organo-metallics are particularly difficult to treat since the lead is not free to form a precipitate.

The organic compound must either be oxidized to free the lead or the compound may be adsorbed on to carbon to remove the lead as the organic complex.

Either way it is difficult and may not be effective.

The equipment used is batch treatment for concentrated wastewater, continuous precipitation for dilute wastewater.

Ion exchange for very dilute solutions or media filtration in the presence of a reducing agent.

For organo-metallic lead, treatability studies should be done to determine if oxidation or carbon adsorption is effective at removing the lead.

New Technologies in Lead Removal from Wastewater

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Lead is often found in wastewater from printed circuit board factories, electronics assembly plants, battery recycling plants and landfill leachate.

In the printed circuit factory, solder plating and etching operations is the lead source.

In the electronics assembly operations, the source is solder flux cleaning.

In battery breaking, the lead is found in the sulfuric acid from the battery.

In landfill leachate, it can be found as an organo metallic like tetra ethyl lead.

A brief description on the latest developments in the process of lead removal from wastewater is listed in this section.

New Technologies in Lead Removal from Wastewater

Lead Removal from Wastewater Using Faujasite Tuff

Removal of Lead from Wastewater Using Emulsion Liquid Membrane Technique

Lead Removal from Wastewater Using Cu(Ii) Polymethacrylate Formed by Gamma Radiation

Removal of Lead Using Tridax Procumbens

Conversion of Oil Shale Ash into Zeolite for Cadmium and Lead Removal from Wastewater

Process Development for the Removal of Lead and Chromium from Aqueous Solutions Using Red Mud—an Aluminium Industry Waste

The Investigation of Lead Removal by Biosorption: An Application at Storage Battery Industry Wastewaters

Use of Granular Slag Columns for Lead Removal

Current Wastewater Treatment Process - Lead Removal

Lead removal from water may be established applying coagulation, sand filtration and ion exchange. Additionally, active carbon, KDF media filtration and reverse osmosis may be applied.

Since lead hydroxide is moderately soluble, it cannot be treated by pH adjustment to regulated concentrations.

It is often treated by precipitating lead sulfide or phosphate, using a two step process.

It can also be treated by reduction or by ion exchange.

When using ion exchange, it is difficult to remove the lead from the resin by regeneration requiring the disposal of the spent resin.

Organo-metallics are particularly difficult to treat since the lead is not free to form a precipitate.

The organic compound must either be oxidized to free the lead or the compound may be adsorbed on to carbon to remove the lead as the organic complex.

Either way it is difficult and may not be effective.
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Lead Removal from Wastewater Using Faujasite Tuff

The Jordanian chabazite-phillipsite tuff and faujasite-phillipsite tuff have suitable mineralogical and technical properties that enable them to be used for ion-exchange processes.

These include suitable grain size and total cation exchange capacity, acceptable zeolite content, good attrition resistance and high packed-bed density.

The chabazite-phillipsite tuff (ZE1 and ZE2) has an excellent efficiency to remove Pb and an acceptable efficiency to remove Fe, Cu, Zn and Ni from effluent wastewater of a battery factory and other industries.

The faujasite-phillipsite tuff (ZE3) is 6.97 times more efficient than the ZE1 and ZE2.

A bed of ZE3 (1,000 kg) loaded in a 1.17-m3 column is capable of cleaning about 2,456 m3 of the effluent from the factory at a cost of US $200/ton.

The wastewater is contaminated with 20 ppm Pb in the presence of competing ions including Ca (210 ppm), Na (1,950 ppm) and Fe (169 ppm).

This quantity of wastewater is equivalent to 120 working days of effluent discharge from the factory at a flow rate of 20 m3/day.1

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Removal of Lead from Wastewater Using Emulsion Liquid Membrane Technique

A detailed study was conducted to remove lead from storage battery industry wastewater by using emulsion liquid membrane (ELM) technique.

The storage battery industry wastewater has an initial lead concentration of 4.2 ppm (average) and a pH value of 1.4.

Emulsion liquid membrane consisted of kerosene and mineral oil as organic solvents, sorbitan monooleate (Span 80) as a surfactant, di-2-ethylhexyl phosphoric acid (D2EHPA) as a carrier or extractant, and sulphuric acid (H2SO4) as a stripping agent.

The important variables affecting the ELM systems, such as organic solvents, surfactant, and carrier concentrations, internal stripping phase normality, external aqueous phase pH value, and normality of organic ligand added, have been investigated systematically.

The system which adjusted to a pH value of 4.0, obtained the maximum lead removal in first 5 min of the treatment studies and exhibited a low turbidity and swelling at the end of the experiment.2

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Lead Removal from Wastewater Using Cu(II) Polymethacrylate Formed by Gamma Radiation

In this work Cu(II) polymethacrylate (Cu(II)PMA) is obtained through gamma irradiation of the corresponding monomer.

The polymer was mixed with Pb(II) aqueous solutions to remove this pollutant from the liquid phase.

The Pb(II) removal occurs via a Langmuir-type adsorption mechanism, that was found to be a function of the contact time between the polymer and the solution.

A 60% decrease of Pb(II) concentration in the liquid phase was achieved. The polymer was characterized using scanning electron microscopy (SEM), energy dispersion analysis (EDX), electron paramagnetic resonance (EPR),X-ray diffraction and FT-IR.

The use of Cu(II)PMA for the treatment of wastewater containing heavy metals is an innovative method that constitutes a simple, effective and economical means for wastewater treatment.3

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Removal of Lead Using Tridax procumbens

A simple cost effective and eco-friendly method for the remediation of lead from industrial wastewater has been investigated.

A novel biomaterial, Tridax procumbens (Asteraceae) a medicinal plant, was used for the removal of lead ions from synthetic wastewater and the method was also applied for real sample analysis.

The operational pH of the experimental solution was fixed as 4.5.

The optimum amount of bioadsorbent was 3.5 g.

The Pb(II) ions removal efficiency of the raw bioadsorbent was also determined.

The removal efficiency of the activated carbon of the bioadsorbent was excellent.

98 % removal of Pb(II) ions was achieved at the dose rate of 3.5 g. The optimum contact time was estimated to be 160 minutes.4

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Conversion of Oil Shale Ash into Zeolite for Cadmium and Lead Removal from Wastewater

A by-product fly ash from oil shale processing was converted into zeolite by alkali hydrothermal activation using sodium hydroxide.

The activation was performed at different activation temperatures using 8 M sodium hydroxide.

The obtained cation exchange capacity (CEC) showed that the best condition for synthesis of zeolite performed in a closed reactor at 160 °C for 24 h.

Powder patterns of X-ray diffraction analysis have shown that zeolite of type Na-PI was successfully synthesized at 29.5, 32.2 and 34.4°.

The produced zeolite was used as an ion exchanger for the treatment of wastewater for metal ions.

Lead and cadmium were chosen as target metal ions.

The adsorption capacity was estimated to be 70.58 mg lead/g-zeolite and 95.6 mg cadmium/g-zeolite when the initial concentration for both ions was 100 mg/l.

The results were correlated using Redlich–Peterson and Sips models.

For cadmium the best fit was obtained with the Sips model while, for lead the Sips models fits the experimental data adequately.

Based on such results, it is concluded that the treated ash may possess strong potentials for zeolite production used in wastewater treatment.5

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Process Development for the Removal of Lead and Chromium from Aqueous Solutions Using Red Mud—an Aluminium Industry Waste

Red mud, an aluminium industry waste, has been converted into an inexpensive and efficient adsorbent and used for the removal of lead and chromium from aqueous solutions.

Effect of various factors on the removal of these metal ions from water (e.g. pH, adsorbent dose, adsorbate concentration, temperature, particle size, etc.) has been studied and discussed.

The effect of presence of other metal ions/surfactants on the removal of Pb2+ and Cr6+has also been studied.

The material exhibits good adsorption capacity and the data follow both Freundlich and Langmuir models.

Thermodynamic parameters indicate the feasibility of the process.

Kinetic studies have been performed to understand the mechanism of adsorption.

Dynamic modelling of lead and chromium removal on red mud has been undertaken and found to follow first-order kinetics.

The rate constant and mass transfer coefficient have also been evaluated under optimum conditions of removal in order to understand the mechanism.

Column studies have been carried out to compare these with batch capacities.

The recovery of Pb2+ and Cr6+ and chemical regenertion of the spent column have also been tried. 6

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Removal and Recovery of Lead (II) from Single and Multimetal (Cd, Cu, Ni, Zn) Solutions by Crop Milling Waste (Black Gram Husk)

The study reports removal of heavy metals when present singly or in binary and ternary systems by the milling agrowaste of Cicer arientinum (chickpea var. black gram) as the biosorbent.

The biosorbent removed heavy metal ions efficiently from aqueous solutions with the selectivity order of Pb > Cd > Zn > Cu > Ni.

The biosorption of metal ions by black gram husk (BGH) increased as the initial metal concentration increased.

Biosorption equilibrium was established within 30 min, which was well described by the Langmuir and Freundlich adsorption isotherms.

The maximum amount of heavy metals (qmax) adsorbed at equilibrium was 49.97, 39.99, 33.81, 25.73 and 19.56 mg/g BGH biomass for Pb, Cd, Zn, Cu and Ni, respectively.

The biosorption capacities were found to be pH dependent and the maximum adsorption occurred at the solution pH 5.

Efficiency of the biosorbent to remove Pb from binary and ternary solutions with Cd, Cu, Ni and Zn was the same level as it was when present singly.

The presence of Pb in the binary and ternary solutions also did not significantly affect the sorption of other metals.

Breakthrough curves for continuous removal of Pb from single, binary and ternary metal solutions are reported for inlet-effluent equilibrium.

Complete desorption of Pb and other metals in single and multimetal solutions was achieved with 0.1 M HCl in both shake flask and fixed bed column studies.

This is the first report of removal of the highly toxic Pb, Cd, and other heavy metals in binary and ternary systems based on the biosorption by an agrowaste.

The potential of application for the treatment of solutions containing these heavy metals in multimetal solutions is indicated. 7

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The Investigation of Lead Removal by Biosorption: An Application at Storage Battery Industry Wastewaters

Lead is present in different types of industrial effluents, being responsible for environmental pollution.

Biosorption has attracted the attention in recent years as an alternative to conventional methods for heavy metal removal from water and wastewater.

The biosorption of Pb(II) ions present in the storage battery industry wastewaters intensively, by Rhizopus arrhizus has been investigated in this study.

This microorganism has been preferred since its biosorption feature was well known.

A detailed study was conducted for the removal of Pb(II) ions which was very toxic even in low quantities to the receiving environment, from storage battery industry wastewater by biosorption system as advanced treatment technique, and to investigate the effects of the several parameters on its removal.

The average Pb(II) ions concentration in the storage battery industry wastewater found 3.0 mg/L and reducing this value below 0.5 mg/L was aimed.

In this study, the effects of the media conditions (pH, temperature, biomass concentration) on the biosorption of Pb(II) ions to R. arrhizus have been investigated in a batch reactor.

Optimum biosorption conditions have been found of initial pH 4.5, temperature 30 °C and biomass concentration 1.0 g/L.

The maximum biosorption capacity was obtained as 2.643 mg Pb(II)/g microorganism.

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8
Use of Granular Slag Columns for Lead Removal

The use of granular blast furnace slag (GBFS)-packed columns to treat lead-containing solutions has been investigated.

The results obtained indicated that the slag usage rate decreased with increasing flow velocity, particle size, initial lead concentration and decreasing with bed height.

Lead removed selectively in the presence of other heavy metal ions. High concentrations of sodium and especially calcium in the solutions impeded the uptake of lead.

For 20 mg l−1 lead concentration an empty bed contact time greater of 4 min provided to efficient use of the slag bed.

Column pH was an important parameter to lead removal under dynamic conditions and reflected the influence of the investigated factors.

During all runs lead breakthrough coincided with an abrupt drop in effluent pH.

The apparent mechanisms of lead removal in GBFS column are sorption (ion exchange and adsorption) on the slag surface and precipitation. 9