Kinetic Studies Of The Adsorption Of Heavy Metal (Chromium) From Industrial Waste Water Using Palm Kernel Shells

Introduction

1.1 Background of Study

Activated carbon is a carbonaceous and crystalline material with a high surface area that makes it appropriate for adsorbing chemical substances that contaminate water or air, depending on its structure. Activated carbon is a microcrystalline , non-graphite form of carbon with porous structure that has been processed to develop its internal porosity, and characterized by large specific surface area of 500-2500m2/g. It is a versatile adsorbent with wide range of uses and applications. The most commonly known use of activated carbon is the purification of water sources. Activated carbon filter is one of several systems used to purify water drawn from wells and springs for home use. It is most effective in the removal of organic substances from water. Its porosity multiplies the surface available to adsorb toxins or react with chemicals (Musal, 2011).

Several agricultural wastes products have been found useful in activated carbon production, like palm kernel shell, coconut shell, rise husk, groundnut husk, cassava peel, maize cob, banana pith, medicagosativa (Alfalfa), sphagnum moss peat, sunflower stalks and others (Nwankwo et al., 2014). Activated carbon can be produced in abundance from oil palm endocarp (or oil palm kernel shell) which is an abundant agricultural solid waste from palm-oil processing mills in many tropical countries such as Nigeria, Malaysia, and Thailand (Silgado et al., 2014).

The use of palm shell as an adsorbent is beneficial because ordinarily, palm shells are considered as waste in many parts of Nigeria, so utilizing them to produce activated carbon is an effective waste management practice. This recycle plan is better than dumping them to pollute the environment or cause environmental or disposal problems.

Another reason why producing activated carbon from agricultural waste is beneficial is because it is very economical especially in a country like Nigeria. So there is no need to worry about purchasing expensive equipment and chemicals to remove chemical waste.

Being a good adsorbent of chemical compounds from industrial waste effluent, activated carbon produced from agricultural products can be used to remove heavy metals from industrial waste water. Different physical and chemical processes are available for removal of heavy metals from waste water, such as co-precipitation, coagulation, evaporation recovery process, electrolytic recovery, electro-chemical precipitation, ultra-filtration, ion exchange, reverse osmosis and biological techniques. A major drawback with precipitation is sludge formation. Ion exchange is a better alternative technique for such purpose, but it is not economically appealing because of high operational cost. The use of activated carbon for the removal of toxic metal ion pollutants and numerous other organic materials from both gases and aqueous solutions is of considerable importance. Activated carbon has proven to be an efficient and cost effective adsorbent (Musah, 2011).

On the other hand, the kinetics of the adsorption process will enable one to determine the rate as well as the mechanism of adsorption processes (Okafor et al., 2015).

1.2 Statement of the Problem

The release of heavy metals into the environment through industrial effluent is a major concern worldwide and removal of such pollutants has been of great concern during the last decades. Heavy metals can pose health hazards to man and aquatic lives. Wastewater commonly contains Chromium, lead, Copper and Nickel ions. These heavy metals are not biodegradable and their presence in stream, lakes leads to bioaccumulations in living organisms, causing health problems in animals, plants and human beings. Therefore, it is of prime importance to remove heavy metals from wastewater that is to be discharged to water bodies.

1.3 Aim and Objectives

1.3.1 Aim

To study the kinetics of the adsorption of heavy metal from industrial waste water using palm kernel shells.

1.3.2 Objectives

1. To prepare a low-cost adsorbent from palm kernel shells.
2. To activate the adsorbent prepared from palm kernel shells.
3. To study the kinetics of the adsorption process.
4. To determine the efficiency of palm kernel shells as an environmentally friendly adsorbent.
5. To characterize activated carbon made from palm kernel shells.

1.4 Significance of Work

With rapid increase in industrial activities, pollution due to the presence of heavy metals in water and wastewaters has been a major cause of concern for environmental engineers. Several episodes of heavy metal contamination in aquatic environment have increased the awareness about heavy metal toxicity. Among these, Minamata tragedy due to mercury poisoning and “Itai-Itai” disease in Japan due to cadmium toxicity are well known. More recently cases of lead poisoning were reported in Zamfara State, Nigeria; which led to the death of several people and animals as a result of lead contamination of water bodies (streams and rivers) and the environment. The presence of heavy metals in the environment is thus of major concern because of their extreme toxicity and tendency for bioaccumulation in the food chain even in relatively low concentration (Adie et al., 2012). So it has become necessary to develop low-cost adsorbent for the removal of heavy metals from industrial effluent. This research work gives the step by step procedure on developing a low-cost adsorbent from palm kernel shells.

1.5 Scope of Work

Although there are several agricultural products (e.g. coconut shell, maize cob, rise husk) used in producing activated carbon, this work only focuses on the use of activated palm kernel shell as heavy metal adsorbent. Heavy metals in industrial wastewater are numerous (e.g. lead ions, cadmium ions, etc.) but this study will only investigate the kinetics of the removal of chromium ion from industrial effluent using palm kernel shells.