Department of Chemistry

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Application of biochar for the removal of actinides and lanthanides from aqueous solutions.
(Elsevier Inc., 2022) Bursztyn, Amalia L. Fuentesa; Arwenyo, Beatrice; Nanney, Andie L.M.; Ramirez, Arissa; Jamison, Hailey; Venson, Beverly; Mohan, Dinesh; Mlsna, Todd E.; Navarathna, Chanaka
Actinides and lanthanides are elements with unfilled f orbitals and are collectively labeled as the inner transition elements (ITEs). The actinide series includes 15 radioactive metallic ele ments with atomic numbers 89–103 (Cooper, 2000). The actinide elements are classified as light (Ac, Th, Pa, U, Np, Pu, Am) or heavy (Cm, Bk, Cf, Es, Fm, Md, No, Lr) based on their atomic numbers. The actinides fill their 5f sublevels progressively and exhibit char acteristics of both the d-block and the f-block elements. Elements of the actinide series can have oxidation states from +2 to plus +7. In addition to being radioactive, all actinides are paramagnetic and pyrophoric. Except for actinium with one oxidation state of +3, the other actinides are known to show variable oxidation states and more than one crystalline phase. To date, only the first four elements in the actinide series have been found to occur naturally.
Contribution of modified P-enriched biochar on pH buffering capacity of acidic soil
(Elsevier Journal of Environmental Management, 2022-11-06) Arwenyo, Beatrice; Varco, Jac J.; Dygert, Andrew; Brown, Sydney; Pittman, Charles U.; Mlsna, Todd
Biochar can directly hold cations in soil because of the negative charge that exists on its surfaces. Besides, improving soil cation exchange capacity, the negative charges on biochar surfaces can buffer acid soil by pro tonation and deprotonation mechanisms. Moreover, biochar ameliorates soil acidity due to the presence of ox ides, carbonates, and hydroxides of its basic cations (Ca, Na, K, and Mg). Both biochar surface functional group and basic cation concentrations can be altered by modification with chemical agents which can affect its soil pH buffering capacity. However, the impact of modified biochar application on soil pH buffering capacity is still scanty. This study investigated the pH buffering capacity of acidic soil amended with three P-enriched modified Douglas fir biochars and compared this buffering capacity to amendment with untreated Douglas fir biochar. These three P-enriched biochars, were prepared by treating Douglas fir biochar (DFB), respectively, with: 1) anhydrous calcium chloride (CaCl2) and potassium phosphate monobasic (KH2PO4), 2) calcium carbonate (CaCO3) and diammonium phosphate {(NH4)2HPO4} and 3) an aqueous solution of magnesium sulfate (MgSO4), potassium hydroxide (KOH) and potassium phosphate monobasic (KH2PO4). The three P-enriched biochars were designated as CCPP, CAPP and MSPP, respectively. The soil pH buffering abilities were largely dependent on the added biochar’s alkalinity and ash contents. The residual soil CEC was highly correlated (r ≥ 0.9), with the soil buffering capacity. Both alkalinity and pH buffering capacity improved following the order CCAP > CCPP > MSPP > DFB, while residual soil CEC followed the order CAPP > MSPP > CCPP > DFB. The pH buffering ca pacity of the soil after amendments with 10% CAPP, CCPP MSPP and BFB rose by 84.8, 58.3, 3.0 and 2.5%, respectively. Whereas MSPP had higher concentrations of K+ and Mg2+, greater concentrations of Ca2+ were present in CCAP and CCPP than MSPP. So, Ca2+ concentrations in biochar exerts a greater influence on alkalinity and buffering capacity than Mg2+ and K+ because of 1) its smaller effective hydration radius and larger charge density. 2) calcium hydroxide has a greater water solubility than magnesium hydroxide providing more available base. Since pH buffering capacity depends on cation exchange sites, soil additives containing Ca2+ are prone to create greater impacts than Mg2+ and K+ additives.
The impact of septic systems density and nearness to spring water points, on water quality
(African Journal of Environmental Science and Technology, 2017-01-18) Arwenyo, B.; Wasswa, J.; Nyeko, M.; Kasozi, G. N.
Worldwide, 1.1 billion people do not have access to clean water and as a result, 2 million children die annually due to preventable waterborne diseases. In Uganda, 440 Children die every week of waterborne diseases. High prevalence of this death is reported in the peri urban areas. It is still unclear however the causes of water pollution in the peri-urban areas. The improper use of onsite sanitation facilities such as latrines and septic systems may lead to groundwater contamination. It is true that drain field of septic system located too close to water point, and or over population of the septic systems in a small area can lead to pollution of groundwater. Our study investigated the impact of septic systems density and nearness to water points on spring water quality. Samples from 15 spring wells were analysed for pH, nitrate and faecal coliform contamination. Locations and distances of spring from septic systems were determined using global positioning system (GPS) device and ArcGIS software, respectively. Water samples from all the spring wells had pH value less than 6.5, 66.7% had faecal coliform and 53% had nitrate above 2 mg L-1. While sample from one of the springs had nitrate concentration above the United States Environmental Protection Agency (US EPA) standard of 10 mg L- 1. It was also noted that coliform counts and nitrate concentrations increases with increase in number of septic systems surrounding the spring well. In addition, increase in distance between spring wells and septic systems indicated decrease in both coliform counts and nitrate concentration. It is therefore concluded that improper use of septic systems is one of the causes of groundwater pollution in the peri urban areas. The study recommends treatments of water from groundwater sources, regular monitoring of groundwater sources and proper design and siting of septic systems using more robust methodologies.
Kinetics and Thermodynamic Studies: Adsorption of Pb, Cr and Ni Ions from Spent Lubrication Oil (SLO) Using Acid Modified Clay
(American Journal of Analytical Chemistry, 2021-12) Sughnen Atsar, Felix; Kukwa, Donald; Ahule Wuana, Raymond; Arwenyo, Beatrice
Adsorption of Pb, Cr, and Ni ions from spent lubrication oil (SLO) by sulphuric acid modified clay (SAMC) was investigated considering the effect of contact time and temperature of the adsorption system. The removal percentage of the heavy metals was found to be temperature and contact time-dependent. Adsorption of the heavy metals increases with an increase in temperature and contact time with 95.0% - 100% adsorption recorded at the temperature of 331 K with the equilibration time of 12 hours. The thermodynamic and kinetics investigation of the adsorption process showed that the adsorption of these metals by the modified adsorbent is a spontaneous and endothermic physical adsorption process that followed the pseudo-second-order kinetic model.
Lead immobilization in simulated polluted soil by Douglas fir biochar-supported phosphate
(Elsevier Chemosphere, 2021-12-16) Varco, Jac J.; Dygert, Andrew; Atsar, Felix S.; Solomon, Sabrina; Venkatesh, Rooban; Thirumalai, K.G.; Pittman Jr., Charles U.; Mlsna, Todd
This study compared the lead (Pb2+) immobilization efficacy of biochar-supported phosphate to conventional in situ heavy metal immobilization methods (with lime, neat biochar and phosphate). The biochar-supported phosphate was obtained by treating Douglas fir biochar (BC) with anhydrous calcium chloride and potassium dihydrogen phosphate. The amount of Pb2+ immobilized was determined by comparing the concentration of ammonium nitrate extractable Pb2+ lead from lead-spiked soil (without amendment) to that of a 30 d incubation with (a) lead-spiked soil plus 5% (wt./wt.) biochar supported-phosphate, (b) lead-spiked soil plus 5% (wt./wt.) untreated Douglas fir biochar, (c) lead-spiked soil plus 5% (w/w) lime and (d) lead-spiked soil plus 5% (wt./wt.) potassium dihydrogen phosphate. The control (lead-spiked soil without amendment) produced the largest quantity (96.08 ± 9.22 mg L− 1 ) of NH4NO3-extractable Pb2+, while lead-spiked soil treated with 5% (wt./wt.) biochar-supported phosphate resulted in the lowest quantity of NH4NO3 extractable Pb2+ (0.3 ± 0.2 mg L− 1 ). The mechanism for immobilization of Pb2+ by BP occurs at pH < 7 through dissolution of hydroxyapatite embedded in BP during modification, followed by precipitation of insoluble Pb10(PO4)6(OH)2. The residual lead fraction in the lead-spiked soil increased by 20.9% following amendment with BP. These results indicate that biocharsupported phosphate is a candidate to reduce lead mobility (bioavailability) in polluted soil. This amendment may lower Pb2+ uptake into plants while minimizing the potential for water contamination due to Pb2+mobility.
Microplastics and Nano-Plastics: From Initiation to Termination
(Journal of Geoscience and Environment Protection, 2023-01-31) Awolesi, Oluwafemi; Oni, Peter; Arwenyo, Beatrice
Following the advent of the Industrial Revolution, plastic pollution has been a serious environmental issue while micro- and nano-plastics have been a cy nosure of researchers’ attention in the twenty-first century. This is due to the improved knowledge of its ecotoxicological effects and the global pushfor ward towards sustainability. There is a growing concern that the increasing presence of microplastics and nanoplastics (MNPs) in aquatic habitats poses a threat to marine life, and it is predicted that nanoplastics will be just as ubi quitous as macro- and micro-plastics, but far more destructive to living or ganisms due to their ability to infiltrate cells. Recent research has shown that marine and freshwater biota become entangled with plastic litter, which dis rupts the ecosystem. Aquatic creatures are known to absorb and deposit these new pollutants in their digestive systems, as has been documented in several studies. More recent research has also examined their co-occurrence and tox icity with other emerging contaminants, including their prevalence and ef fects in food, air, and soil. Using articles extracted from a six-year period from Scopus, ACS Publications and Google Scholar, this review explores the origins, fates, occurrence in the food chain, exposure routes, cellular interac tions of microplastics and nano-plastics, in addition to the ecotoxicological impacts, analytical methods, and the potential remedies for combating pollu tion and toxicity. Ultimately, this review is a comprehensive, updated adden dum to available reviews on micro- and nano-plastics.
PFAS: Ecological Implications, Remedial Actions and Ethical Considerations
(Journal of Agricultural Chemistry and Environment, 2023-08-31) Awolesi, Oluwafemi; Oni, Peter; Oshinowo, Abiodun; Olubusoye, Boluwatife S.; Owusu, Faustina; Pama, Simeon Sunday; Osobamiro, Temitope; Ongwech, Acaye; Awolesi, Omotoyosi; Arwenyo, Beatrice
The C-F bond is one of the strongest in organic chemistry. It is responsible for the great stability of perfluoroalkyl and polyfluoroalkyl substances, commonly referred to as “PFAS”, a group of man-made chemicals that include perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Thermal stability, surface activity, dielectric characteristics, chemical resistance, and inertness are just a few of the technical advantages that this group has over hydrocarbons, and since the 1950s, these chemicals have been largely utilized in a variety of domestic and industrial endeavors. The hydrophilic and lipophilic nature of this class of chemicals accounts for its uniqueness. Up until today, the chemistry and ecotoxicology of these chemicals continue to emerge. Issues concerning the destructive power of ignorance expedited by an ineffective regulatory institution continue to show that manufacturing chemicals are insufficient without giving serious thought to issues of openness and humanity’s awareness of its own safety. When discussing the nature of humanity and how it can be defined or redefined, it is important to allude to the significance of integrating business with ethics in its various forms. This paper highlights the importance of holding polluters accountable for PFAS contamination cleanup costs while emphasizing the need for chemical manufacturers to test and disclose the health and environmental effects of PFAS compounds. In addition, the sources, types, properties, applications, distribution, toxicological implications, regulations, and analytical methods associated with PFAS (per- and polyfluoroalkyl substances) are explored. The effectiveness of the remedial methods described in this paper needs to be progressively tested while exploring other sustainable approaches.
Phosphorus availability from magnesium-modified P-enriched Douglas fir biochar as a controlled release fertilizer
(Soil Use and Management, 2021-08-04) Arwenyo, Beatrice ; Varco, Jac J.; Dygert, Andrew ; Mlsna, Todd
Phosphorus (P) is one of the essential elements required for plant growth and de velopment. However, worldwide, many agricultural soils can be deficient in P. The use of fertilizers and manures as a source of P can be costly, limited in sup ply in some regions of the world and ecologically unfavourable. Nutrient-enriched biochar has been suggested as a relatively cost-effective and eco-friendly P source. This study investigated P availability from Douglas fir biochar modified with mag nesium chloride and potassium hydroxide solutions only (B), and modified P enriched Douglas fir biochar B50, B100 and B150 corresponding to B treated with 50, 100 and 150 mg P L−1 solutions of potassium phosphate monobasic. Triple super phosphate fertilizer (FC) and a control treatment without phosphate added (C) used as a reference treatment. Treatments were added to soil in varied amounts to obtain the same P rate of 30 kg P ha−1. Aboveground biomass dry weight yield (R2 = .7) and plant height (R2 = .86) improved with P contents. After harvest, re sidual soil P for the FC treatment was significantly greater than all other treatments (p-value = 1.7848 E-6, R2 = .8). Plant height and aboveground dry weight biomass were greater with B150 compared to B50 at the same total P loading, suggesting that the greater P concentration of the biochar (B150) resulted in less tightly bound P and was therefore more available for plant uptake. This study showed promise of utilizing P-enriched Douglas fir biochar as a slow-release P fertilizer.
Sorption of Phosphate on Douglas Fir Biochar Treated with Magnesium Chloride and Potassium Hydroxide for Soil Amendments
(MDPI Processes, 2023-01-19) Arwenyo, Beatrice; Navarathna, Chanaka; Krishna, Naba Das; Hitt, Addie; Mlsna, Todd
With increasing climate variability, a sustainable crop production approach remains an indispensable concern across the globe. In this study, P retention/availability of MgCl2.6H2O/KOH modified Douglas fir biochar was assessed. The MgCl2·6H2O/KOH treated Douglas fir biochar was prepared by sequentially treating Douglas fir biochar with magnesium chloride and potassium hy droxide solutions. The biochar’s surface area, pore volume, morphology, and elemental composi tions were determined using BET, SEM, SEM/EDS, and powder X-ray analyzes. Both surface area and pore volume were reduced by more than 97% following modification. Similarly, the morphol ogy and elemental compositions changed after modification. The maximum P adsorbed correspond ing to Langmuir–Freundlich model was 41.18 mg g−1 . P sorption on biochar soil mixture was pH dependent. More studies are required to establish the field applicability of P-laden MgCl2 ·6H2O/KOH-modified Douglas fir biochar as a soil additive.
Speciation of heavy metals in water from the Uganda side of Lake Victoria
(Tailor and Francis, 2010-02) MBABAZI, JOLOCAM; TWINOMUHWEZI, H.; WASSWA, J.; NTALE, M.; MULONGO, G.; KWETEGYEKA, J.; SCHR DER, K.H.
Different forms of copper Cu, zinc Zn, lead Pb and cadmium Cd in water from the Uganda side of Lake Victoria (25°C, pH 6.75–7.18), the second largest inland freshwater lake in the world, have been studied using ion-exchange, dialysis and atomic absorption spectrophotometry. The results indicate that heavy metals Cu, Zn, Pb and Cd are present mainly in the cationic form (80–83%). Small quantities of anionic (13–22%), non-ionic, dialyzable (4–8%), and non-ionic, non-dialyzable (< 1.3–4.4%) forms were also detected for all metals except Cd. The corresponding concentrations lay in the ranges: cationic, 0.06–0.99; anionic, < 0.001–0.25; non-ionic, dialyzable, < 0.001–0.08; non-ionic, non-dialyzable, < 0.001–0.06 µg ml−1 . The existence of the metals in non-ionic and nondialyzable forms is attributable to metal associations with high relative molecular mass (RMM) organic matters.
Stannate (IV) and Antimonate (V) Hexahydroxy-anion complexes with Di- and Polyhydric Phenols
(Research Journal of Chemical Sciences, 2011-05-02) Mbabazi, Jolocam; Ntale, M.; Kwetegyeka, J.; Mulongo, G.; Twinomuhwezi, H.; Nnamuyomba, P
An identification has been achieved of only 1:1 and 1:2 chelates of hexahydroxystannate (IV) anions with ortho (i.e., 1,2)-diphenols, using potentiometric and conductimetric techniques. Lack of evidence for organo-richer complexes in aqueous media is in contrast to antimonite (V) hexahydroxy anions and tellurate (VI), which are each able to form a tris (catecholate).
Sustainable Biochar for Water and Wastewater Treatment
(Elsevier Inc. All rights reserved, 2022) Mohan, Dinesh (editor); Pittman Jr., Charles U.(editor); Mlsna, Todd E. (editor)
This First Edition was motivated by the recent enormous growth in biochar research. From 2010 to the date this Preface was written, the Web of Science database shows 18,224 publica tions on biochar have appeared. This activity is accelerating. In 2010, 119 publications appeared. This grew to 3975 in 2020. By September 2021, 3588 biochar papers had already been counted for that year. The first use of biochar, as distinct from charcoal or activated carbon, for water remediation appeared in the Jour nal of Colloid and Interface Science in 2007 [JCIS, 310(1)2007, 57–73]. Fast pyrolysis by-product biochar obtained from biooil production in an auger-fed reactor was used to remove heavy metals from water. Following this publication, many reports on slow and fast pyrolysis biochar as a substitute for activated carbon in water purification have appeared. Previously, biochar had been used for soil enrichment and carbon sequestration.
Uptake of Phosphorus from Modified P-Enriched Douglas Fir Biochar and Its Effects on Crop Growth and P Use Efficiency
(Journal of Geoscience and Environment Protection, 2022-09-29) Arwenyo, Beatrice; Varco, Jac J.; Dygert, Andrew; Berry, Jaime; Mills, Julianna; Mohan, Dinesh; Pittman, Charles U.; Mlsna, Todd
The potential use of biochar as a sustainable soil amendment has recently gained global recognition. The use of biochar as a soil additive is attributed to its ability to improve soil chemical, physical and biological properties. Studies have shown that biochar amendments can enhance soil nutrient retention and availability, pH, water holding capacity, microbial activity and sequester car bon. In this study using corn (Zea mays L.) as an experimental crop, the in fluence of P availability from modified P enriched Douglas fir biochar (PEB), triple super phosphate fertilizer (SPF), and modified Douglas fir biochar (MB) on plant growth and P Use Efficiency (PUE) were compared. The rate of P applied (0, 30, 60, 90 and 120 kg·ha−1 ) was calculated based on % P content of each soil additive. Except for MB treatments, P recovery, crop growth and P Use Efficiency increased with application rates. The maximum above ground dry matter yields corresponding to PEB, SPF and MB treatments were esti mated at 3488 kg·ha−1 , 2449 kg·ha−1 and 639 kg·ha−1 , while their respective agronomic P use efficiency (AGE) rates were 32 kg·kg−1 , 17 kg·kg−1 , 0.5 kg·kg−1 . Also, recovery of K, Mg, Ca, Zn, Fe, Cu, B and Mn improved in both PEB (p value < 0.0003, r2 > 0.9) and SPF (p value < 0.0058, r2 > 0.9) treatments. More studies at field scale are needed to demonstrate the practicability of using modified P enriched Douglas fir biochar for soil amendments.

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