Hydrogen is a component of spacecraft fuel that is explosive at atmospheric concentrations of four percent or higher. A study was undertaken to determine potential systems for use in tow types of hydrogen sensors that will be useful for real time hydrogen detection, both in ground storage and utilization facilities and in spacecraft. Quantitative detection demands a small, highly sensitive, and highly selective sensor. These detectors will be useful in areas such as the vicinity of joints, couplings, and stress points in the hydrogen storage and plumbing system of the space shuttle. Qualitative detection requires the other sensor to cover large areas, use no power, and be easily monitored visually or with a camera. Such a sensor will serve two purposes: it will allow general detection of hydrogen in a large space where poorly positioned point sensors would fail; it will also aid in locating and repairing any hydrogen leaks that might occur. A manganese (IV) oxide film was produced on the surface of a quartz crystal microbalance and this system was investigated for use as a small, quantitative hydrogen sensor. A reproducible response to hydrogen in the form of an increase in the frequency of vibration of the quartz crystal under an applied voltage was demonstrated. Other coatings were also investigated. A number of indicator compounds were screened for response to hydrogen to serve as large area sesnors. The metallochromic indicator, calmagite, produced a noticeable darkening upon exposure to hydrogen, demonstrating its potential for use as a qualitative, large area hydrogen sensor.

This PhD thesis deals with the analysis of perovskite-based catalysts for the removal of soot and CO from the exhaust of highly efficient automotive gasoline engines. The study is primarily focused on the development of two series of samples obtained by the partial substitution of the Ba cation in BaMnO3 (BM) and BaMn0.7Cu0.3O3 (BMC), that is, with the general formula Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A), being A Ca, Ce, La, Mg or Sr. Subsequently, the activity of these samples as catalysts for the oxidation of soot and CO, in conditions simulating that found in the exhaust of automotive gasoline engines, has been estimated. Then after, in order to obtain the best composition of perovskites for soot oxidation, the optimal degree of Ba cation substitution for the two selected compositions (BM-Ce and BMC-La) has been explored by the synthesis of Ba1-xCexMnO3 (BM-Cex) and Ba1-xLaxCu0.3Mn0.7O3 (BMC-Lax) perovskite-type mixed oxides at different substitution levels (x = 0, 0.1, 0.3, 0.6). These catalysts were deeply characterized and used for GDI soot oxidation. Based on the results presented and discussed in the three published articles, corresponding to Ba0.9A0.1MnO3 (BM-A) and Ba0.9A0.1Mn0.7Cu0.3O3 (BMC-A) series, the following general conclusion have been extracted: - The hexagonal structure is preferred in the presence of A metal, as it is the main phase detected for BM-A, and, as the polytype structure found in the BMC sample (formed by distortion of the hexagonal perovskite due to the copper insertion into the lattice) is disfavored in BMC-A perovskites that present a mixture of the two structures. - On the surface of all perovskites, coexisting Mn(IV), Mn(III) and oxygen vacancies. Mn(IV) is the main oxidation state on the surface of all samples, but, in the bulk, it depends of the A metal and on the perovskite formulation: i) for BM-A series, Mn(III) is more abundant for BM-Ca and Mn(IV) is for BM-Mg, being both oxidation states in similar proportion for the other samples and ii) for BMC-A series, Mn(IV) is the main one for BMC-Ce and BMC-Mg, while Mn(III) was for BMC and BMC-La. - The partial substitution of Ba in BM and BMC: i) enhances the reducibility, being BM-La the most reducible sample from BM-A series (being the unique which evolves oxygen at intermediated temperature, ’-O2) and BMC-Ce from BMC-A series and ii) improves the lattice oxygen mobility, being Ce the most efficient A metal due to the contribution of the Ce(IV)/Ce(III) pair. - Almost all perovskites are active as catalysts for soot removal by oxidation, as most of the TPR-soot conversion profiles are shifted to lower temperatures in the presence of perovskites in the two atmospheres tested (0%and 1% O2 in He). However, the soot conversion is notably lower in the absence of O2 than in the presence of an 1% O2 in the reaction mixture, as the oxygen available for soot oxidation exclusively comes from the bulk of perovskites. In these conditions, BMC-La is the most active catalyst as presents the highest proportion of copper on the surface (as Ba-O-Cu species). In the presence of oxygen (1% O2 in He), BM-Ce is the best catalyst as it shows a high amount of oxygen surface vacancies, the highest oxygen mobility, and the best redox properties due to the additional participation of the Ce(IV)/Ce(III) pair which promotes the O2 emission from the bulk of perovskites, which seems being directly involved in the soot oxidation. - The role of copper seems to be relevant only if the oxygen used for the soot oxidation exclusively comes from the perovskite (i.e., in 100% He), as BMC-La, which presents the highest fraction of surface copper, is the most active catalyst. On the contrary, if soot is oxidized using the oxygen present in the reaction atmosphere (i.e., in 1% O2 in He), the presence of copper in the perovskite composition is not significant, as the most active catalyst is BM-Ce because it shows a higher fraction of surface Ce(IV) than BMC-Ce and, consequently, a better redox performance. - All BM-A and BMC-A perovskites are catalytically active for the oxidation of CO under all the reaction conditions tested, being more active in the gaseous mixtures with low CO/O2 ratios and showing the highest activity in 0.1% CO and 10% O2. - The addition of A metal increased the catalytic activity for the oxidation of CO at T < 500 °C with respect to BM and BMC, but BMC-A samples show the highest efficiency as catalysts for CO oxidation due to the presence of copper. For BM-A series, BM-La is the most effective to improve the catalytic performance as it this the most reducible and because generates ά-O2. For BMC-A series, BMC-Ce is the most active catalyst as it combines the presence of surface copper, oxygen vacancies, a high proportion of bulk and surface Mn(IV), and the contribution of the Ce(IV)/Ce(III) pair. - BMC-Ce perovskites presents at 200 °C, and using the 0.1% CO + 10%O2 gas mixture, a CO conversion very similar than the Pt-Al reference catalyst. From the un published results obtained for Ba0.9Ce0.1MnO3 (BM-Cex) and Ba0.9La0.1Cu0.3Mn0.7O3 (BMC-Lax) perovskites (with different substitution levels x = 0, 0.1, 0.3, 0.6), the following conclusions are proposed: - The characterization of BM-Cex series reveals that: i) as the percentage of Ce increases, the hexagonal perovskite structure is progressively replaced by CeO2 crystalline phase, which is the main one for BM-Ce0.6 , ii) Mn(IV) is the main oxidation state on surface for BM and BM-Ce0.1, but it is Mn(III) for BM-Ce0.3, while for BM-Ce0.6, an almost similar amount of Mn(III) and Mn(IV) are present, iii) Ce(III) and Ce(IV) coexist on the surface of all BM-Cex samples, and a considerable increase in the surface Ce(IV) proportion is detected from BM-Ce0.1 to BM-Ce0.6, iv) after doping with Ce, the reduction of Mn/Ce takes place at lower temperatures due to the synergetic effect between Mn and Ce and, finally, v) the oxygen mobility through the perovskite lattice increases in the presence of Ce (due to the contribution of Ce(IV)/Ce(III) pair) and all samples evolve -O2, but only BM-Ce0.1 generates a low amount of α´-O2. - The characterization of BMC-Lax series indicates that: i) as the percentage of lanthanum increases, the intensity of XRD peaks corresponding to BaMnO3 polytype structure decreases in favor of an increase in the intensity of the peaks corresponding to hexagonal 2H-BaMnO3 and trigonal La0.93MnO3 perovskite structures, being the latter the main phase for BMC-La0.6, ii) the amount of surface oxygen vacancies seems not to be sensible to the increase in the La amount, iii) Mn (III) and Mn (IV) coexist on the surface and in the bulk, but, on the surface Mn(III) increases with the La content, while in the bulk Mn(IV) is favored as La content is higher, iv) the accumulation of Cu (II) on the surface increases with the amount of La, v) an increase in the reducibility of BMC-La0.3 and BMC-La0.6 samples respect BMC and BMC-La0.1 is found, and, finally, vi) the oxygen mobility increases with the percentage of La. - The analysis of the catalytic performance for soot oxidation in the two conditions tested suggests that: i) in the absence of oxygen in the reaction atmosphere (100 % He), BMC-La0.1 is the best catalyst as copper is also able to catalyze the soot oxidation, ii) if oxygen is present in the reaction atmosphere (1 % O2 /He), BM-Ce0.1 is the most active catalyst as it presents a higher proportion of Mn(IV) than BMC-La0.1. - The addition of an amount of Ce or La higher than the corresponding to x=0.1 in Ba1-xCexMnO3 and Ba1-xLaxCu0.3Mn0.7O3 does not allow improving the catalytic performance of BM-Ce0.1 and BMC-La0.1 for soot oxidation in the tested conditions.

No description available.

Ligands prepared from various combinations of aldehydes and ketones with the appropriate aminealcohol were complexed with cupric acetate monohydrate. The complexes with O,NO or N,N,O donor atoms were synthesized to study the influences of the ligand on molecular structure, spin-spin interaction, and on the value of the exchange integral. The magnetic data indicated that of the eight Cu(II) complexes discussed, two behaved differently from known analogous compounds. Cu (benzoylacetone :ethanolamine) was compared to Cu(acac:ethanolamine), and Cu(pyrr:oaminophenol) was compared to Cu(acac:o-aminophenol). Each pair of complexes was postulated to have the same molecular structure. The synthesis and characterization of Mn(pyrr:oaminophenol) 2H2 is also discussed. The following physical data were collected and discussed: elemental analysis, melting point, molecular weight, infrared spectra, electronic spectra, and magnetic susceptibility.

Mounted ill. Offprint of the author's journal article in pocket. Includes bibliographies.

Three effective solutions to dissolve the filter cake created by water-based drilling fluids weighted with Mn3O4 particles were developed. Hydrochloric acid at concentration lower than 5 wt% can dissolve most of Mn3O4-based filter cake. Dissolving the filter cake in two-stage treatment of enzyme and organic acid was effective and eliminated the associated drawbacks of using HCl. Finally, combining low and safe concentration of HCl with an organic acid in one-stage treatment was very effective. Hydrochloric acid (10-wt%) dissolved 78 wt% of Mn3O4-based filter cake at 250°F after 28 hours soaking time. However, Chlorine gas was detected during the reaction of 5 to 15-wt% HCl with Mn3O4 particles. At 190°F, 1- and 4-wt% HCl dissolved most Mn3O4 particles (up to 70-wt% solubility). Their reactions with Mn3O4 particles followed Eq. 8 at 190°F, which further confirmed the absence of chlorine gas production at HCl concentrations lower than 5-wt%. EDTA and DTPA at high pH (12) and acetic, propionic, butyric, and gluconic acids at low pH (3-5) showed very low solubilities of Mn3O4 particles. GLDA, citric, oxalic, and tartaric acids produced large amount of white precipitation upon the reactions with Mn3O4 particles. Similarly, DTPA will produce damaging material if used to dissolve Mn3O4-based filter cake in sandstone formation. At 4-wt% acid concentration, lactic, glycolic, and formic acids dissolved Mn3O4 particles up to 76 wt% solubility at 190°F. Malonic acid at lower concentration (2-wt%) dissolved 54 wt% of Mn3O4 particles at 190°F. Manganese tetraoxide particles were covered with polymeric material (starch), which significantly reduced the solubility of filter cake in organic acids. Therefore, there was a need to remove Mn3O4-based filter cake in two-stage treatment. Enzyme-A (10-wt%) and Precursor of lactic acid (12.5-wt%) dissolved 84 wt% of the filter cake. An innovative approach led to complete solubility of Mn3O4 particles when low and safe concentration of HCl (1-wt%) combined with 4-wt% lactic acid at 190°F. HCl (1-wt%) combined with lactic acid (4-wt%), dissolved 85 wt% of the Mn3O4-based filter cake after 18-22 hours soaking time at 250°F in one stage treatment.

Mounted ill. / Offprint of the author's journal article in pocket / Includes bibliographies / xiii, 248 leaves, [50] leaves of plates, [3] folded leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, 1985

Thesis (Ph.D.)--Mississippi State University. College of Veterinary Medicine. / Title from title screen. Includes bibliographical references.

Electrical double-layer formed at the electrode/electrolyte interface in combination with electron-transfer reaction can lead to many important applications of electrochemistry, including energy storage devices, namely, batteries, fuel cells and electrochemical supercapacitors. Electrochemical supercapacitors are characterized by their higher power density as compared to batteries and higher energy density than the conventional electrostatic and electrolytic capacitors. Thus, supercapacitors are useful as auxiliary energy storage devices along with primary sources such as batteries or fuel cells for the purpose of power enhancement in short pulse applications. These are expected to be useful in hybrid devices together with batteries or fuel cells, in electric vehicle propulsion systems. Among the various materials studied for electrochemical supercapacitors, carbonaceous materials, transition metal oxides and conducting polymers are important. Carbon in various forms is used as a double-layer capacitor material, which stores charge by electrostatic charge separation at the electrode/electrolyte interface. The specific capacitance (SC) of high surface area activated carbon is about 100 F g-1 in aqueous electrolytes. Transition metal oxides have attracted considerable attention as electrode materials for supercapacitors because of the following merits: variable oxidation state, good chemical and electrochemical stability, ease of preparation and convenience in handling. Hydrated RuO2 prepared by sol-gel process exhibited a SC as high as 720 F g-1. However, high cost, low porosity and toxic nature of RuO2 limit its commercialization in supercapacitors. On the otherhand, MnO2 is an attractive electrode material as it is electrochemically active, cheap, environmentally benign, and its resources are abundant in nature. In an early report on the capacitance properties of MnO2 by Lee and Goodenough [J. Solid State Chem. 144 (1999) 220], amorphous hydrous MnO2 synthesized by co-precipitation method exhibited a SC of 203 F g-1 in 2 M KCl electrolyte. According to the charge-storage mechanism of MnO2 involving MnO2 + M+ + e- ↔ (MnOO)-M+ (where M+ = Li+, Na+, K+ etc.), a SC of 1110 F g-1 is expected over a potential window of 1.0 V. However, SC values in the range of 100-200 F g-1 are reported in the literature. The low values of SC are because of the charge-storage is confined to surface region of MnO2 particles or films. It is desirable to enhance the SC of MnO2 to a value close to the theoretical value. In view of this, attempts are made to enhance the SC of MnO2 by adopting different synthetic procedures such as electrochemical method for depositing MnO2 and also nanostructured mesoporous MnO2 by polyol route, hydrothermal route and sonochemical method in the present studies. As the charge-storage mechanism of MnO2 involves the surface insertion/deinsertion of cations from the electrolyte during discharge/charge processes, respectively, the capacitance properties of MnO2 are studied in various aqueous electrolytes containing monovalent (Na+), bivalent (Mg2+, Ca2+, Sr2+ and Ba2+) and trivalent (La3+) cations. The mass variation occurring at the electrode during the charge/discharge of MnO2 is examined by electrochemical quartz crystal microbalance (EQCM) study. In addition to this, the kinetics of electrodeposition and capacitance properties of Mn(OH)2 are studied by employing EQCM. Also, properties of asymmetric capacitors assembled with Mn(OH)2 as the positive electrode and carbon as the negative electrode are studied and compared with symmetric Mn(OH)2 capacitors. Furthermore, attempts are made to increase the potential window of Co(OH)2 in alkaline and neutral electrolytes. The contents of the thesis by Chapter-wise are given below. Chapter 1 introduces the importance of electrochemistry in energy storage and conversion, basics of electrochemical power sources, importance of some electroactive materials in electrochemical energy storage, different synthetic procedures for MnO2 and its application in electrochemical supercapacitors. Transition metal oxides are widely studied because of their variable oxidation states, high electrochemical activity, abundance in nature and environmental compatibility. Various reports appeared in the form of open publications on supercapacitor studies of transition metal oxides such as RuO2, MnO2, Fe3O4, Co(OH)2, Ni(OH)2, NiO, etc., are briefly reviewed. The chapter ends with statements on objectives of the studies carried out and reported in the thesis. Chapter 2 provides experimental procedures and methodologies used for the studies reported in the thesis. Different experimental routes adopted for synthesis of MnO2, Mn(OH)2 and Co(OH)2 used for the studies are described. Also included are brief descriptions of various physicochemical and electrochemical techniques employed for the investigations. In Chapter 3, MnO2 samples synthesized by various routes such as electrochemical method, polyol route, hydrothermal route and sonochemical method are studied. MnO2 and Mn(OH)2 are simultaneously electrodeposited on the anode and the cathode, respectively, in a galvanostatic electrolysis cell consisting of aqueous Mn(NO3)2 electrolyte. MnO2/SS and Mn(OH)2/SS electrodes are used as the negative and the positive electrodes, respectively, in an asymmetric Mn(OH)2//MnO2 supercapacitor. MnO2 samples are prepared at room temperature and in hydrothermal method at a temperature of 140 ◦C by reduction of KMnO4 with poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG) or P123 as a reductant. Also, MnO2 is prepared from KMnO4 by hydrothermal method without using any reducing agent. This procedure requires a temperature of 180 ◦C and 24 h duration. MnO2 is also synthesized with an ultrasonic aided procedure. The electrochemical capacitance properties of MnO2 samples synthesized by various routes are investigated. A maximum SC of 264 F g-1 is obtained at a current density of 0.5 mA cm-2 (1.0 A g-1) for MnO2 prepared by sonochemical method. The capacitance properties of MnO2 are generally studied in neutral aqueous Na2SO4 electrolytes. In Chapter 4, electrolytes of NaNO3, Mg(NO3)2, Ca(NO3)2, Sr(NO3)2, Ba(NO3)2 and also La(NO3)3 are studied and the results are compared with Na2SO4 electrolyte. Among the alkaline earth salt solutions, higher SC values are obtained in Mg(NO3)2 and Ca(NO3)2 electrolytes than in the rest of the electrolytes. Furthermore, MnO2 exhibits capacitance behaviour in La(NO3)3 solution with enhanced SC in comparison with NaNO3 and Mg(NO3)2 solutions. The SC increases with an increase in charge on the cation (Na+, Mg2+ and La3+). The values of SC measured in Na+, Mg2+ and La3+ electrolytes are 190, 220 and 257 F g-1, respectively at a c.d. of 0.5 mA cm-2 (1.0 A g-1). Rate capabilities are also found to be different in different electrolytes. Specific energy and specific power are calculated and presented as Ragone plots. The presence of divalent and trivalent cations inserted onto MnO2 is identified by X-ray photoelectron spectroscopy. EQCM is employed to monitor the increased mass variations that accompany reversible adsorption/desorption of Na+, Mg2+ and La3+ ions onto MnO2. In Chapter 5, EQCM has been used to study the kinetics of electrochemical precipitation of Mn(OH)2 on Au-crystal and its capacitance properties. From the EQCM data, it is inferred that NO3- ions get adsorbed on Au-crystal, and then undergo reduction resulting an increase in pH near the electrode surface. Precipitation of Mn2+ occurs as Mn(OH)2, resulting an increase in mass of the Au-crystal. On charging, Mn(OH)2 undergoes oxidation to MnO2, which exhibits electrochemical supercapacitor behaviour on subjecting to cycling in aqueous Na2SO4 electrolyte. EQCM data indicates the mass variations corresponding to surface insertion/extraction of Na+ ions during discharge/charge cycling of Mn(OH)2 in aqueous Na2SO4 electrolyte. In Chapter 6, Mn(OH)2 synthesized by precipitation of MnSO4 with NH4OH solution is studied for capacitance properties. A SC of 141 F g-1 is obtained for the Mn(OH)2 at a c.d. of 0.66 A g-1 in 1.0 M Na2SO4 electrolyte in the potential range of 0-1.0 V vs. standard calomel electrode (SCE). Also, carbon electrode made from high surface area carbon exhibits a SC of 158 F g-1 at a c.d. of 0.81 A g-1 in the potential range of 0 to -1.0 V vs. SCE. Asymmetric capacitors are assembled by combining Mn(OH)2 as the positive and carbon as the negative electrodes. The asymmetric capacitor has a SC of 39 F g-1 at a c.d. of 0.42 A g-1 in the operating voltage of 1.8 V. However, a symmetric capacitor consisting of two Mn(OH)2 electrodes provides a SC of 11 F g-1 only at a c.d. of 0.24 A g-1 in an operating voltage of 1.2 V. In Chapter 7, MnO2 synthesized by reduction of KMnO4 using ethylene glycol is used for fabrication of large area electrodes. Stainless steel (SS) mesh of 3 cm x 3 cm with geometrical area of 18 cm2 is used as current collector. Three symmetrical electrochemical supercapacitors (capacitance of about 100 F per each at a current of 0.2 A) are assembled, each with 11 electrodes positioned in parallel. Six alternate electrodes are stacked as the negative terminal and the other five as the positive terminal. The electrochemical properties of MnO2 supercapacitors are studied by galvanostatic charge-discharge cycling and ac impedance in 1.0 M Na2SO4 electrolyte. Also, the capacitors are combined in parallel as well as in series and the capacitance is evaluated. The practical application of the electrochemical supercapacitors is shown by demonstrating the running of a toy fan connected to the charged capacitor as well as the glowing of LED cell connected to charged supercapacitors connected in series. A parallel combination of batteries and capacitors is also demonstrated. Capacitor studies of Co(OH)2 over a limited potential window in alkaline electrolytes are reported in the literature. A high potential window of a capacitor material is desirable for using in a device. In Chapter 8, experiments are conducted to understand the reason for a low potential window for Co(OH)2 as a capacitor material and also to increase its potential window. Experiments are conducted in aqueous NaOH and Na2SO4 electrolytes of various concentrations using electrochemically precipitated Co(OH)2 on stainless steel current collectors in an aqueous Co(NO3)2 electrolyte. Based on the potential window, specific capacitance and specific energy, it is found that 0.05 M NaOH electrolyte is more appropriate for capacitor properties of Co(OH)2 than the rest of the electrolytes studied. Using a Co(OH)2 electrode with a specific mass of 1.0 mg cm-2 in 0.05 M NaOH, a SC of about 380 F g-1 is obtained with a potential window of 0.85 V at a charge-discharge c.d. of 10 A g-1 (10 mA cm-2). The work presented in this thesis is carried out by the candidate as a part of Ph. D. training program and most of the results have been published in the literature. A list of publications of the candidate is enclosed below. It is hoped that the studies reported here will constitute a worthwhile contribution.

D. Tech (Department of Chemistry, Faculty of Applied and Computer Sciences) Vaal University of Technology. / Trivalent arsenic (As(III)) and hexavalent chromium (Cr(VI)) toxicity have necessitated a great deal of research into the remediation of contaminated water. The techniques applied including oxidation, coagulation-flocculation and ion exchange have suffered drawbacks due to the high cost of materials and equipment, complex operations and secondary pollution among others. Adsorption, however, remains a cost-effective solution in the remediation of contaminated water. The use of biosorbent materials further lowers the cost of the adsorption process and improves its eco-friendliness. These biomaterials, however, suffer some drawbacks as poor porosity, low adsorption capacities and mechanical strength thus require modifications to improve their applicability as biosorbents. In this work pine cone powder, a waste from pine trees, was used as a biosorbent for the removal of As(III) and Cr(VI) from water. The powder was pre-treated with Fenton’s reagent to oxidize some of the functional groups and provide more binding sites. Iron oxide magnetic nanoparticles (magnetite) were incorporated into the pine cone matrix to form a magnetic composite with higher heavy metal affinity. The magnetite nanoparticles were also doped with manganese to improve their redox capacities and aid in the oxidation of the toxic As(III) to the less toxic As(V) and allow for improved binding. The adsorbents used in the study were therefore named as Fenton’s treated pine cone powder (FTP), pine cone -magnetite composite (FTP-MNP), magnetite nanoparticles (MNP), manganese doped magnetite nanoparticles (Mn MNP) and manganese doped pine cone-magnetite composite (Mn FTP-MNP). The prepared materials were fully characterized, and the adsorption process was optimized for both As(III) and Cr(VI) removal from aqueous solution. After modification the surface area of the particles increased in the order Mn MNP>MNP>Mn FTP-MNP>FTP-MNP>FTP. Surface and Xray analysis confirmed the formation of magnetite by the presence of both ferric and ferrous ion states on the surface and characteristic diffraction peaks for magnetite. The adsorption data was fitted into isotherm and kinetic models and the nature of adsorption was determined from the thermodynamic and kinetic parameters. Equilibrium studies indicated that the adsorption followed Langmuir isotherm for all adsorbents and was thus monolayer in nature, further analysis indicated that chemisorption was the predominant type of adsorption with ion exchange being the predominant mechanism of adsorption. Spent adsorbents were tested for reusability and displayed excellent adsorption capacities when used for up to three times. Adsorption mechanism was evaluated using characterization techniques and the ion-exchange mechanism inferred from thermodynamic data was confirmed spectroscopically with redox reactions aiding in the removal of the pollutants from water. The introduction of competing anions in solution, lowered the adsorption efficiency of both arsenic and chromium on the adsorbent indicating that there was competition for adsorption sites.