ADSORPTION OF CHROMIUM(VI) AND COPPER(II) IONS FROM WELL WATER IN CHALLAWA INDUSTRIAL AREA USING PECTIN-CHITOSAN POLYELECTROLYTE COMPLEX

ABSTRACT

The  aim  of  the  research  was  to  carryout  adsorption  study  of  the  removal  of chromium(vi) and copper(ii) ions from well water using pectin-chitosan polyelectrolyte complex as adsorbent. The optimum pH and ratio of pectin/chitosan was determined and the chitosan/pectin complex was characterized by using FTIR, BET, XRD, and SEM. Finally, removal efficiency of the PEC for chromium and copper was studied under optimum conditions. I.e. 0.4 g adsorbent mass, 1.221 and 0.12 mg/L of initial copper and chromium concentration respectively, 60 oC temperature and 30 mins of time.  Result  shows  that  the  optimum  pectin/chitosan  ratio  and  pH  of  the  medium required to produce PEC with high removal efficiency was pH: 4 and pectin/chitosan ratio: 1:3. The active groups identified from FTIR are NH2  group and OH group from carboxylate group, with particle size 2 nm and surface area was 377 m2/g from BET.

When the optimum temperature was 60 ℃, adsorption time of 30mins and the amount of adsorbent was 0.4g, the results showed that the adsorption capacities of the PEC of Cu2+ and Cr6+ were 333.33 and 270.27 mg/g respectively when the initial concentration was  1.221  and  0.12  mg/L  respectively.  The  fitting  results  of  Langmuir  isothermal model,  the  pseudo  second  order  kinetic  model  and  the  copper  and  chromium’s ∆Gowhich had negative values and ∆Ho  of 53.39 and 51.67KJ.mol-1  respectively and ∆So  of 0.163 and 0.167 J.mol-1K-1  respectively of thermodynamics data of the ions adsorption process show that the adsorption of heavy metal ions of Cu2+ and Cr6+ by the PEC is a spontaneous process of single-layer chemisorption.

CHAPTER ONE

1.0  INTRODUCTION

1.1 Background of Study

The demand for water is on the increase and this is attributed to an increase in human population. Similarly, a large fraction of this water is been used for other industrial processes (Basheer, 2018). However, the quality and availability of usable water is on the decline as the introduction of pollutants from industrial process has led to a decrease in the quality of water as well as making this water toxic and unsafe for consumption (Basheer, 2018).

According to Radaideh et al. (2017) industries such as electroplating, hospitals, pharmaceuticals, power plant, refineries, leather tanning, mining, dyes and pigments, steel fabrication, canning and inorganic chemical production plants are at the helm of affairs in the release of toxins which contaminate water.

This has brought about the need to purify these contaminated waters of which methods such as filtration, screening, oxidation, precipitation, coagulation, centrifugation, flotation, crystallization, sedimentation, distillation, evaporation, reverse osmosis, electro-chemical, ion exchange and adsorption are at the forefront (Sabino et al., 2016). However, the high operational and maintenance costs, generation of toxic sludge and complicated procedure involved in the implementation of any of the separation methods listed  above  has  put  a  damper  on  their  use  (Sabino  et  al.,  2016).  However,  the adsorption process does not suffer from this constrains and its ease of operation and simplicity of design gives it an edge over other separation techniques (Czikkely et al., 2018).

The  numerous  toxins  been  released  by  numerous  industrial  processes  particular attention is given to the release of heavy metals as this metal’s possess a great threat to the environment. Heavy metals (metals and metalloids with a density greater than 5 g/cm3  with atomic weights between 63.5 and 200.6 and a specific gravity greater than

5.0 such as Copper (Cu), Chromium (Cr), Cadmium (Cd), Lead (Pb), Nickel (Ni) been

amongst the most prevailing heavy metals (Chen et al., 2018; Singh & Gupta, 2016).

According to Sabino et al. (2016) and Arie et al. (2018) factors such as the technical applicability, cost-effectiveness, selectivity, good chemical and thermal properties, reusability, low solubility in the contacting fluid as well as favorable kinetics, thermodynamics and transport properties are all pointers to what a good adsorbent should be. The desire for that perfect adsorbent has necessitated the need for research into different types of adsorbent and their impact on the adsorption process in general (Ambali  et  al.,  2015).  A  typical  classification  of  adsorbents  categorizes  them  as activated carbons, activated alumina, silica gel, clays, zeolite and hydrogels (Ambali et al., 2015).

The guiding principle in adsorption is the interaction between functional groups which exist on the surface of the adsorbent and metal ions. This interaction leads to the formation of complexes where the heavy metal ions attach themselves to the functional groups (Hastuti et al., 2016). Adsorbents can be classified as either nature derived adsorbents or synthetic adsorbents with preference been given to nature-derived adsorbents. Different natural polymers have been used as adsorbents including pectin and chitosan (Chirani et al., 2015).

Pectin is a compound widely found in plant cell. It is a polymer of D-galacturonic acid linked by 1,4 glycosidic bond and widely available in the middle lamella of plant cell

walls its functional groups include hydroxyl, carboxyl, amide and methoxy while chitosan on the other hand (which is obtained from deacetylation of chitin compounds) is a cationic copolymer of glucosamine and N-acetylglucosamine is a derivative of chitin which is extracted from the skin of crustaceans, such as shrimp and crab. The presence of amine and hydroxyl functional groups makes it a suitable adsorbent (Hastuti et al., 2016). The formation of a polyelectrolyte complex (PEC) which is simply the incorporation of chitosan with pectin to fabricate the composite material called polyelectrolyte complex (PEC) this incorporation exploits both the functional groups of both the pectin and chitosan leading to the formation of a highly functionalized composite material.

1.2 Statement of the Research Problem

The presence of heavy metals in drinking water has caused serious health hazards to humans. The need to combat this environmental challenge treatment measures such as precipitation,  electrochemical  removal  has  been  proposed,  but  this  conventional methods have significant disadvantages, some of which are incomplete removal of contaminants, high energy requirements, sludge etc. The search for low cost adsorbent especially from waste materials has intensified. Pectin and chitosan are direct waste materials from crustaceans which has been estimated to be 1.5 million ton per annum (Chen et al., 2016)  and orange peel which has been estimated to be 25 million ton per annum (Ana et al., 2011) respectively and has been considered to be good adsorbents.

1.3 Aim and Objectives

The aim of the study is the Adsorption of chromium(vi) and Copper(ii) ions from well

Water in Challawa Industrial Area using Pectin-Chitosan Polyelectrolyte Complex

The objectives were to:

I.    Optimize the effect of pH and ratio on the synthesis of PEC.

II.    Characterize PEC to determine its morphology, functional group, surface area, pore size, pore volume, and crystallinity.

III.    Conduct batch adsorption studies of the effect  of operating parameters such as temperature, effect of time, adsorbent dosage, adsorption isotherms, kinetics and thermodynamics

1.4 Justification for the Study

The utilization of pectin and chitosan will check environmental and aquatic pollutant such as shells of shrimps, snail, crabs which are in abundance in riverine areas and orange  peel  which  are  by products  of  orange  juice  industry.  Adsorption  is  a  cost effective method for removing contaminants, the use of chitosan and pectin are a promising material to be used as adsorbent due to their efficiencies.

1.5 Scope of Work

This research work is limited to the optimization of the effect of ratio and pH on the synthesis PEC, characterization of PEC as well as the adsorption of heavy metals by using PEC as an adsorbent.

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