OPTIMIZATION STUDIES OF PROCESS PARAMETERS FOR THE ADSORPTION OF COPPER AND ARSENIC IONS FROM SIMULATED WASTE WATER USING CHITOSAN AND CHITOSAN – ZEOLITE BEADS

ABSTRACT

This research presents the “Optimization Studies of Process Parameters for the Adsorption of Copper and Arsenic Ions from Simulated Waste Water using Chitosan and Chitosan – Zeolite Beads” which was achieved by developing adsorbents of chitosan and chitosan – zeolite composite beads under acidic and alkaline conditions such as acetic acid and sodium hydroxide mediums. The prepared adsorbents were characterized using X – Ray Diffraction, Brunauer Emmett Test, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. The SEM result of chitosan Zeolite has homogenous, cubic crystals and smooth flaky surface evenly distributed in the composite while that of Chitosan beads  surface was relatively rough, irregular in shapes and shows presence of agglomerate particles. The mean crystallite size of Chitosan-Zeolite and Chitosan beads were obtained as 41.64 and 74.45 nm. And the BET result shows that the surface area of the Chitosan and Chitosan- Zeolite beads were found to be 376.40 m2/g and 691.10 m2/g respectively. Using the central composite design, the effect of the parameters such as adsorbent dosage, initial concentration, temperature and time on the adsorption rate of the heavy metal (Copper and arsenic) from the simulated waste  water was investigated. The optimal  conditions obtained for both adsorbents (chitosan beads and chitosan – zeolite beads) on copper removal were 0.5g, 0.5M, 500C and 80mins which translated to 98.03 and 99.78% removal and which also resulted to 96.22 and 99.10% removal respectively. The combined effect of adsorbent dosage and temperature and the combined effect of temperature and time from the four parameters studied for Chitosan beads were found to have the greatest impact on Copper and Arsenic removal while the combined effect of initial concentration and time and that of adsorbent dosage and initial concentration were also found to have the greatest impact on both Copper and Arsenic removal based on their F- values which were found to be (7.27 for Cu and 9.58 for As) removal using Chitosan beads while (17 .20 for Cu and 8.69  for As) removal for Chitosan – Zeolite beads  . IR spectrum analysis suggested the different functional groups which are present in the Chitosan and Chitosan- Zeolite beads to be –CONH-, -CH2 and – CH3, C-O, stretching N-H bending, -NHC00CH3 and -NH bending. Batch adsorption studies on Chitosan- Zeolite beads for Copper and Arsenic removal showed significant effects on the variables adsorbent dosage, equilibrium time (90 min), initial metals concentration, pH and temperature. The results provide a good indication of the different operating conditions that would be required for efficient removal of Copper and Arsenic from aqueous solution. The isotherm parameters obtained from models revealed that Langmuir was the best isotherm that best described the adsorption process with the highest respective Correlation Coefficient R2 value of 0.998 and 0.981 for Copper and Arsenic removal on Chitosan- Zeolite beads. The Copper and Arsenic adsorption process on Chitosan- Zeolite beads kinetics data were best modelled by pseudo second order kinetics with the R2 value 0.999 even at different temperatures. The thermodynamic constants, ΔG, ΔH and ΔS of the adsorption process showed that adsorption of the both metal on the adsorbent were endothermic, spontaneous and is built on the principle of physical adsorption which is caused by van der waals forces a relatively weak bond.

CHAPTER ONE

1.0      INTRODUCTION

1.1       Background to the Study

In recent years there has been an increase in the release of heavy metals into the surroundings leading to the contamination of ground water as a result of advancement in industrialization and urbanization. This has led to a great problem of environmental pollution worldwide (Gupta et al., 2011). The presence of heavy metals in minute concentrations plays an important role in the metabolic activities and growth of plants and animals. However, increased concentrations of heavy metals may have several toxicological effects on many life forms (Pahlavanzadeh et al., 2012).

The most hazardous chemical industries are those that deals with heavy metals such as chromium (Cr), Nickel(Ni), Cadium (Cd), Arsenic (As), Lead (Pb) and Copper (Cu). These industries (Example is the metallurgical industries i.e steel industries, and the non – ferrous mining industries) released large amount of heavy metals which contaminates potable clean water and kill aquatic organism due to their high rates of solubility.

As reported by (Mabrouk et., al  2010), the adsorption of heavy metals at concentrations above threshold limit into food chains by ingestion can result to serious health related problems. Hence, the treatment of heavy metal contaminated wastewater is a very important step prior to the emission or release to the environment.

Conventional  treatment  processes  such  as  ion  exchange,  electrochemical  removal  and precipitation can be employed in the elimination of heavy metal from inorganic effluent. It is noteworthy to mention that each of these processes have their various disadvantages which includes: creation of toxic sludge, partial removal and sometimes high energy consumption. (Auta and Hammed, 2011).

Recent study for the quest of effective and inexpensive technologies which utilized low cost adsorbent has been intensified. One of such alternative for effluent treatment is adsorption (Auta and Hammed,2011). Adsorption process is a suitable technique for inorganic and organic pollutants removal from wastewater, because of the significant advantages like low- cost, availability, profitability, ease of operation, efficiency, and effectiveness than other techniques (Sarra et al., 2014; Gupta et al., 2011). Adsorption process involves separation of a substance from one phase and its accumulation at another surface. This technique is easy to operate and equally effective in the removal of toxic pollutants, even at low concentrations (Amuda and Edewor, 2013). Though many techniques can be used for the treatment of inorganic effluent, the ideal treatment should not only be suitable, appropriate and applicable to the local conditions but also able to meet the Maximum Contaminant Level (MCL) standards established.

The various adsorbent may be in different forms which could be organic or may have biological origin, minerals, industrial byproduct, biomass, polymeric materials and agricultural waste (Kumari et al., 2016). The commercial activated carbon most widely used as an adsorbent has become economically less feasible owing to its relatively high cost. Recently, different low cost bio sorbent sourced from natural materials and biological wastes from industrial processes has been studied for the development of cheap and effective metal sorbents (Sethu et al., 2010). Among these low cost adsorbents, chitosan has the highest sorption capacity for several metal ions (Amuda et al., 2013).

Chitosan is obtained from Chitin (2-acetamido-2deoxy- d-glucose-(N-accetylglucan) which is the main structural component of molluscs, insects, crustaceans, fungi, algae and marine invertebrates like crabs and shrimps (Amuda et al., 2013). It has been reported that approximately 49000 tons of scales per year rounding up to about 2% of fish weight are produced during de – scaling process of fish (Boddu et al., 2008). Fish scales contains connecting tissues, protein, collagen embodied with calcium salt such as calcium carbonate and phosphate, 41% – 84% protein content (Boddu et al., 2008).

Chitin is one of the most abundant and most important natural polysaccharide which has been described to be produced on a yearly basis as much as cellulose found in shells and cell walls of fungi (Zakaria et al., 2011).

Zeolites are crystalline in nature, could be found naturally in the earth’s crust or sodium silicate and also can be synthesized under hydrothermal conditions from solutions sodium aluminate. Usually crystalline aluminosilicates with pores of molecular dimensions with high surface area and ordered pore structure. Zeolite which is a multi – purpose material normally source from clay is mostly for engineering purposes one which is adsorption owing to the fact that its molecules have similar diameter order, diameter larger than pore diameter or aperture are separated from entering the pores. However, it is only zeolites that are technically well – prepared that can give optimum performance during its application.

Yang and Zall (1984) reported that chitosan can chelate five to six times greater concentrations of metals than chitin. They further reported this property to be related to the free amino groups exposed in chitosan because of deacetylation of chitin. Chitosan is slightly soluble at low PH and possesses problems for developing commercial applications. Also, the active binding sites of chitosan are not readily available for sorption. The sites are reported to be soft and have a tendency to agglomerate or form gel in aqueous solutions. Transport of metal contaminants to the binding sites plays a very important role in process design. Therefore, it is necessary to provide physical support and increase the accessibility of the metal binding sites for process applications. Ascertaining the best operating condition and optimal percentage removal of Copper and Arsenic using Chitosan and Chitosan – Zeolite beads from simulated waste water based on process parameters such as time, adsorbent dosage, initial concentration and temperature so as to ascertain necessitated this research study Also, investigating the mechanism of adsorption kinetics and thermodynamic studies gave an insight of the entire process.

1.2       Statement of the  Research Problem

Water pollution is a source of danger to the health of people living in developing countries such as Nigeria. However, industrially generated waste water containing heavy metals such as (Cr), Nickel (Ni), Cadmium (Cd), Arsenic (As), Lead (Pb) and Copper (Cu), Iron (Fe) and Zinc (Zn) have been reported to be potentially harmful and not eco-friendly to the human body system, this is due to their unique composition and content, and if not properly treated or recycled prior to the release for domestic usage , it ultimately results in various health related issues such as cardiomyopathy, Anemia, kidney damage, memory loss, edema, horizontal lines on nails and miscarriages in women.

There is the need for further studies on how these harmful metals could efficiently or totally eliminated using better and readily available adsorbents such Chitosan and Zeolite. Other techniques used for removal of heavy metals are rather inadequate, expensive and generate lot sludge.

1.3       Justification for the Study

Research interest arise as a result of production of alternative adsorbents to replace the expensive adsorbents. Besides, using other techniques for the removal of heavy metal with low concentration apart from them not being suitable also generates a lot of sludge. In view of these, recent study suggests that the use of naturally occurring material like chitosan, zeolite as adsorbents for the remov of heavy metals will be adequate and give remarkable efficiency owing to its regenerating ability, high adsorption capacity, economically viable and also help to reduce the negative effect of this toxic metal in the environment. Consequently, chitosan offers a lot of promising benefits for wastewater treatment and applications today.

1.6       Aims and Objectives of the Study

The aim of this research is to develop chitosan beads and chitosan – zeolite composite beads for the removal copper and arsenic from simulated wastewater. The objectives of the study are to :

1.    Develop adsorbent using chitosan and chitosan – zeolite beads under alkaline and acidic conditions.

2.    Characterize   adsorbents   using   X-ray   diffraction   (XRD),   Scanning   Electron Microscope (SEM) and Fourier transformation infrared (FT-IR) for crystal size, surface morphology and surface functional groups respectively.

3.   Determine the percentage removal of  Copper  and Arsenic using the  developed adsorbents based on time, temperature, initial concentration and adsorbent dosage.

4.   Carry out the Kinetic, Thermodynamic, and Isotherm study of the heavy metals removal from simulated wastewater using the developed adsorbents.

5.   Determine Optimal conditions to obtain the highest percent removal of Copper and Arsenic using Central Composite Design (CCD).

1.7       Scope of the Study

This research was limited to development of adsorbents (Chitosan Beads and Chitosan– Zeolite Beads), characterized and forming of composite. The developed chitosan composite was optimized and used for removal of heavy metals from simulated wastewater. Adsorption isotherms, kinetic and thermodynamic study were also carried out.

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