APPLICATION OF CRUDE BIOMASS AND EXTRACTED CELLULOSE FROM MANGO LEAVES IN THE TREATMENT OF WASTEWATER

ABSTRACT

Lack of sufficient safe drinking water remains a major challenge world over. Further, population growth and subsequent growth in agriculture, industry and technology continues to contribute to increased contamination of the little available clean water everyday. Major contaminants include, agro-chemical residuals, industrial effluents, acids, dyes and toxic heavy metals. Heavy metals of concern includes lead and cadmium because at even very low levels are toxic and have no known metabolism in the body. Literature findings have established a direct correlation between the level of turbidity and microbial load. convectional methods fall short because they are expensive or not readily available. The current work sought to establish a low cost effective adsorbent by utilizing mango (Mangifera indica L.) kernels agricultural waste as a resource to prepare adsorbent materials. Biomass, MBM was obtained by grinding dried kernels, ash, MKA was obtained by burning M.indica kernels in presence of oxygen in a furnace at 600ºC. Carbon, MKC and activated carbon, MKAC, were prepared by pyrolysis of dried kernels and activated kernels in a furnace at 400ºC, respectively. The materials obtained were utilized for the adsorption of lead and cadmium ions and turbidity from wastewaters. Batch experiments were carried out to determine the effect of contact time, initial concentration of metal ions, dosage, temperature and pH on the percentage removal of Pb²⁺, Cd²⁺ and turbidity on the four adsorbents. The adsorption capacity for Pb²⁺ was 8.73 for MKAC, 5.69 for MKC, 9.69 for MKA and 4.69 for MBM and 12.76, 7.13, 12.71 and 3.8 for MKAC, MKC, MKA and MBM, respectively for Cd²⁺. MKAC, MKC and MKA fitted well in Freundlich adsorption isotherm model for Pb²⁺ and Cd²⁺ with R² values of 0.989 for

MKAC, 0.993 for MKC and 0.978 for MKA with Pb²⁺ and 0.974, 0.987 and 0.914 for MKAC, MKC and MKA, respectively for Cd²⁺. MBM fitted in the Langmuir model with R² value of 0.983 and 0.997 for Pb²⁺ and Cd²⁺, respectively. Highest percentage turbidity removal were 54.82, 31.63, 97.37 and 59.97 for MKAC, MKC, MKA and MBM, respectively. Products derived from M. indica kernel were found to be effective adsorbents.

CHAPTER ONE

INTRODUCTION

 1.1 Background Information

Industrial waste constitutes the major source of various kinds of metal pollution in natural waters. Rapid industrialization has led to increase in disposal of heavy metals into the environment. According to Wasewar (2010), mining activities, agricultural run-off, industrial and domestic effluents are mainly responsible for the increase of the metals released into the environment. Metals released into the environment tend to persist indefinitely accumulating in living tissues throughout the food chain and are posing threat to the environment and public health (Aksu and Kutsa, 1991). Heavy metals like lead and cadmium are present in low concentrations in wastewaters and are difficult to remove from water. Once in the body there is no known metabolism or excretion of the heavy metals.

There are many methods employed to remove and recover the metals from the environment and many physio-chemical methods have been proposed for removal and recovery of heavy metals from wastewaters (Barakat, 2011). They include; adsorption, microbial degradation, chemical oxidation, precipitation, ion exchange and solvent extraction. Adsorption is an effective method of removing heavy metals from industrial effluents. Adsorbents such as activated carbon, silicates, aluminates and cellulose can be used. Activated carbon is effective due to its large number of pores, large surface area relative to the size of the actual carbon particle and visible exterior surface and high degree of porosity making it most versatile adsorbent to be used for effective removal of organic solids that have extraordinary large internal surface and pore volume. Its unique pore structures play an important role in many different liquid and gas phase application.

Adsorption processes offer an effective alternative approach for lead, cadmium, and turbidity remediation owing to the lower initial cost, sludge free, clean, simple design and operation, easy recovery and insensitivity to toxic pollutants. Most agricultural solid wastes are inexpensive, abundant, easily available and eco- friendly. Consequently many researchers have focused on the feasibility of low-cost materials that were derived from agricultural wastes for the removal of various dyes, heavy metals and other pollutants (Budinova et al., 2006). Wastes and industrial by-products can be used directly or after modification as adsorbents.

An adsorbent can be termed as a low cost adsorbent if it requires little processing, is provided in nature or is a by-product of waste materials. Generally plant biomass exist as cellulosic surfaces, that have partially negative charges in water. They posses columbic interaction with cationic species in water (Mckay et al., 1987). The high binding abilities of cationic species on the adsorbents are mainly the result of columbic interactions. Due to the sorption properties possessed by cellulosic materials,many agricultural wastes have been used for removal of various organic and inorganic compounds.

Complete removal or reduction of lead to acceptable concentration has become a major challenge in environmental protection. According to Zhaoquin (2013) it is difficult for lead to be biodegraded. Consequently, development of potentially lowcost adsorbents with high adsorption capacity is critical for heavy metal removal.

Many materials such as synthetic resin, green macro algae, bagasse fly ash and water hyacinth have been used as adsorbents. The current study aimed at producing ecofriendly low cost adsorbent from M. indica kernels.

1.2 Statement of the problem

Kenya is a water scarce country and the large population lacks access to safe, clean drinking water. Population, industrial and economic growth has led to increased pollution and pressure on water. The little available water has been contaminated and there is need to purify it for human consumption. Lead and cadmium are key contaminants and are highly toxic. The adsorption characteristics of lead and cadmium using various adsorbents have been investigated for purposes of separation and purification. The adsorbents used which include carbonized beet pulp, peat, fly ash and bentonite are expensive or not readily available.

There is therefore need to prepare a low cost yet effective adsorption material. In the local markets, there are a lot of agricultural wastes like M. indica kernels which do not decay easily. There is a need to find ways of reducing these solid wastes and converting the otherwise pollutants into useful materials. Activated carbon processed from M. indica kernels would be cost effective in removing lead, cadmium and turbidity from wastewaters at the same time controlling solid wastes from market places.

1.3 Justification of the Study

The availability of safe clean drinking water is a major concern in Kenya. The high level of pollution and inadequate treatment of wastewater has enhanced the water crisis in our nation. Lead and cadmium being persistent in the environment have contributed to water contamination. There is need to develop adsorbents for these heavy metals to ensure safe drinking water to Kenyan growing population. Agricultural solid wastes like chaff, rice husk, sesame, sunflower and tea wastes have been used to remove lead from waste waters (Kafia and Surchi, 2011). Also pineapple stem waste has been used to remove basic dye (methylene blue) by adsorption (Hameed et al., 2009). Since M. indica kernels are readily available agricultural wastes, they were utilized as adsorbents for lead, cadmium and turbidity removal in this research work.

1.4 Hypothesis

Biomass, charcoal, activated charcoal and ash prepared from M. indica kernels are effective adsorbents for lead, cadmium and turbidity.

1.5 General objective

The main aim of the study was to determine efficiency and capacity of charcoal, activated charcoal, ashes and biomass generated from M.indica kernels in removal of lead, cadmium and turbidity from water.

1.6 Specific objectives

1. To determine percentage removal of Pb²⁺ and Cd²⁺ from water using charcoal, activated carbon, ash and biomass from indica kernels while varying contact time, initial metal concentration, adsorbent dose, temperature and pH.
2. To determine the optimum adsorption capacities of charcoal, activated carbon, ash and biomass from M. indica kernels for lead and cadmium ions from water.

• To determine the coagulation capacity of charcoal, activated carbon, ash and biomass from indica kernels towards removal of turbidity.

1.7 Significance of the Study

Agricultural solid waste disposal is a concern in the country. Mismanagement of these wastes results in pollution of the natural environment and may posse substantial danger to public health and welfare. The study aimed at producing a cheaper adsorbate to purify wastewaters by utilizing agricultural waste products that are responsible for solid waste in our local markets. Therefore the study converted the otherwise waste into cost effective adsorbent at the same time enhancing green chemistry.

 APPLICATION OF CRUDE BIOMASS AND EXTRACTED CELLULOSE FROM MANGO LEAVES IN THE TREATMENT OF WASTEWATER