Journal of Hazardous, Toxic, and Radioactive Waste

In the present study, sugarcane bagasse (Saccharum officinarum) was utilized to assess its capacity for the adsorption of fluoride from aqueous solutions. The batch adsorption experiments were carried out to calculate the adsorption capacity of sugarcane bagasse for the adsorption of fluoride from aqueous solution. The effects of various parameters like initial pH (${\mathrm{pH}}_0$), adsorbent dose ($m$), contact time ($t$), initial concentration ($C_0$), and temperature ($T$) on the adsorption of fluoride from the aqueous solution were studied. The adsorption rate is found to be very fast. For $C_0=4\mathrm{mg}/\mathrm{L}$, about 45% fluoride removal was found in $t=60\min$ contact time at $m=1\mathrm{g}/\mathrm{L}$ adsorbent dose. The sorption kinetics could be well represented by a pseudosecond-order kinetic model. The minimum uptake of fluoride was found to be $1.20\mathrm{mg}/\mathrm{g}$, maximum uptake was observed to be $1.82\mathrm{mg}/\mathrm{g}$ at lower concentration ($4\mathrm{mg}/\mathrm{L}$). At higher concentration ($8\mathrm{mg}/\mathrm{L}$), the minimum uptake of fluoride was found to be $2.50\mathrm{mg}/\mathrm{g}$ and maximum uptake of fluoride was found to be $4.12\mathrm{mg}/\mathrm{g}$. Pseudo first-order, pseudo second-order, Elovich and modified Freundlich equations were used to describe the adsorption rate of fluoride. Adsorption isotherms have been studied by Langmuir, Freundlich, Temkin, Redlich-Peterson, and Toth, and Radke-Prausnitz equations and their constants were determined. Thermodynamic parameters such as $\mathrm{\Delta }G°$, $\mathrm{\Delta }H°$, and $\mathrm{\Delta }S°$ were calculated in order to understand the nature of sorption. A thermodynamic study revealed that the adsorption of fluoride onto bagasse is an endothermic process.

An optimization model is developed to locate pumping wells in a river bank filtration system to minimize the overall cost of pumping and treatment. The model combines the numerical solution of water flow and solute transport from the river to the pumping wells with a genetic-algorithm-based optimization technique. The water quality parameters considered in the study are the concentration of (1) suspended solids, (2) endosulfan, which is a widely used pesticide in agriculture, and (3) E. coli. It was observed that the fitness function increases at a faster rate near the river before attaining the optimum. However, the rate of decrease in the fitness function is gradual after the optimum. It is concluded that the genetic-algorithm-based optimization technique is an efficient and robust in the estimation of optimum well distance. Sensitivity analysis of the optimal distance and total cost due to variation in aquifer characteristics and decay rate is also presented.

In this investigation, the effect of replacing some percentage of natural coarse aggregate with recycled concrete aggregate (RCA) in geopolymer concrete synthesis is studied. The study focuses on the compressive strength and release of elements from the geopolymer concrete samples. The toxicity characteristic leaching procedure (TCLP) was used to determine release of potentially hazardous heavy metals (PHHMs) and other constituents of potential concern (COPCs) from the geopolymer concrete and also to identify if the material should be categorized as either hazardous or nonhazardous. It was found that replacing virgin aggregates with RCA had a small impact on the compressive strength of the concrete, reducing it by a maximum of 34%. As measured by toxicity characteristics leaching procedure (TCLP), release of As was reduced by adding RCA. The leached concentrations of the elements, Ba, Cd, Cr, and Pb were found to be below TCLP regulatory limits.

Libya has dealt with a high number of radioactive sources since the end of the 1950s when oil exploration processes started. Today, there are more than 125 facilities in the country tha use radioactive sources for medical applications, in the oil and gas industry, and in educational institutions. Libya also has a research reactor, with nominal power of 10 MW, that has been operated by the Tajura Nuclear Research Centre (TNRC) since 1983; in addition, the TNRC produces and uses a number of radioactive sources. Naturally occurring radioactive material (NORM) is also present in Libya, and they are primarily produced from the exploration and operations within the oil and gas industry. To maximize the protection of the environment and human health from the detrimental effects of radioactive waste (RW) in Libya, efforts have been made to develop and implement a sufficient and effective RW management (RWM) system. The Libyan RWM system consists of: the Libyan national policy for RWM, legislative framework, and RWM facilities. This study will explain the Libyan system of RWM and, moreover, evaluate the current state of RWM in the country using a strength, weaknesses, opportunities, and threats (SWOT) analysis methodology to draw conclusions and recommendations.

This study aims to generate a database on the radioactivity content of the building materials mined and used in Tiruchirappalli District employing a high-resolution NaI(Tl) detector. Ninety-two different types of building materials were collected from the local construction suppliers. The results indicated that ${}^{226}\mathrm{Ra}$, ${}^{232}\mathrm{Th}$, and ${}^{40}\mathrm{K}$ concentrations in the building materials of the study area were found to vary from below detection limit (BDL) to $367.2\mathrm{Bq}/\mathrm{kg}$, BDL to $190.3\mathrm{Bq}/\mathrm{kg}$, and BDL to $\mathrm{1,227}\mathrm{Bq}/\mathrm{kg}$, respectively, with arithmetic mean values of $45.5\mathrm{Bq}/\mathrm{kg}$, $73.5\mathrm{Bq}/\mathrm{kg}$, and $302.6\mathrm{Bq}/\mathrm{kg}$. Other radiation hazard indices, like radium-equivalent activity, absorbed dose rate, external and internal hazard indices, indoor and outdoor effective doses, and radioactivity level index, were also calculated. Building materials such as phosphogypsum, granite tiles, and fly ash show a higher level of radium-equivalent activity ($>370\mathrm{Bq}/\mathrm{kg}$) and $I_{\gamma }$ activity ($>1$). Hence, the use of phosphogypsum, granite tiles, and fly ash samples needs to be avoided, and all the other building materials mined and used from this district posed no radiological risk to human populations.

This paper discusses the efficacy of zero-valent iron nanoparticles (ZVIN), magnetic iron oxide nanoparticles (MIN), zero-valent iron nanoparticles/tea waste composite (ZVIN-TW), magnetic iron oxide nanoparticles/tea waste composite (MIN-TW), zero-valent iron nanoparticles/sugarcane bagasse composite (ZVIN-SB) and magnetic iron oxide nanoparticles/sugarcane bagasse composite (MIN-SB) in the removal of trivalent chromium ions. The effect of pH, adsorbent dosage, time, and initial metal ion concentration on removal efficiency was studied. The maximum chromium uptake was obtained when the pH, adsorbent dosage, and initial metal ion concentration were respectively 6, $0.1\mathrm{g}/100\mathrm{mL}$, and $250\mathrm{mg}/\mathrm{L}$. The experimental uptake capacity of ZVIN, MIN, ZVIN-TW, MIN-TW, ZVIN-SB, and MIN-SB was found to be 231.19, 232.59, 219.94, 232.08, 244.18, and $245.68\mathrm{mg}/\mathrm{g}$, respectively. The experimental data fitted well with Langmuir isotherm (Type I) and pseudo-second-order kinetics. The activation energy analyzed using a D–R isotherm was found to be 12.34, 12.65, 12.12, 12.95, 14.40, and $14.22\mathrm{kJ}/\mathrm{mol}$ respectively for ZVIN, MIN, ZVIN-TW, MIN-TW, ZVIN-SB, and MIN-SB. The results of intraparticle diffusion and Boyd’s study showed that film diffusion and chemical reaction controlled the overall adsorption process. Ion exchange, hydrogen bonding, and electrostatic attraction were found to be the three major mechanisms involved in the adsorption. Investigation on temperature variation confirmed the adsorption process. The presence of cations and anions affected the adsorption response. The nanoparticles and nanobiocomposites were characterized by point of zero charge (${\mathrm{pH}}_{\text{pzc}}$), ultraviolet visible spectroscopy, Brunauer–Emmett–Teller surface area analysis, X-ray powder diffraction study, Fourier transform infrared (FTIR) spectral study, scanning electron microscopy, energy dispersive X-ray spectroscopy analysis, atomic force microscopy (AFM) studies, and vibrating sample magnetometer (VSM) analysis. AFM images showed a triangular morphology in ZVIN and MIN for particle sizes of 296.8 and 263 nm, respectively. FTIR study revealed hydroxyl, carboxyl, iron, and other compounds to be the functional groups. VSM analysis showed the superparamagnetic nature of MIN, MIN-TW, and MIN-SB. Nanoparticles and nanobiocomposites were found to be effective adsorbents.

Use of contaminant mass discharge (CMD) or mass-flux measurements to characterize site conditions and assess remediation performance of nonaqueous phase liquid (NAPL) is becoming popular. The main objective of this study is to determine how groundwater flux variations in the source zone can affect nonaqueous phase liquid (NAPL) dissolution dynamics. In particular, the authors develop interplays among groundwater flux variations, NAPL aqueous concentration, NAPL CMD, and other source strength dynamics. A power-law functional form is used to describe groundwater flux variations in illustrating how NAPL source strength functions can be affected. The developed analytical models can capture a wide range of NAPL source zone dynamics encountered in real-world applications. The results demonstrate the significance of groundwater flux variations in influencing the NAPL source dynamics. If groundwater flux decreases with time, the CMD declines initially at higher rate, but the rate decreases at later stages. In contrast, when groundwater flux increases with time, the NAPL CMD exhibits a slower decline initially and faster decrease at later stage. When groundwater flux in the source zone increases with time, the reduction in CMD (CMDR) increases slower than the NAPL mass reduction (MR), leading to a concave downward CMDR versus MR curve. If groundwater flux decreases with time, the CMDR versus MR curve is convex upward. When the groundwater flux does not change with time, CMDR versus MR follows a 1:1 linear relationship. The models are also compared with the observed dynamics of a trichloroethene (TCE) contaminated field. Although the root mean square error (RMSE) for the TCE aqueous concentration does not change much for both the constant and variable groundwater flux conditions, that for the CMD can be reduced significantly using the model of power-law groundwater flux variations.

Radioactive sources have been in use in Ghana over the last six decades, mainly in medicine, agriculture, industry, research, and academic investigations. Radioactive sources declared “disused” by users are required to be transferred to the Centralized Waste Processing and Storage facility of the National Radioactive Waste Management Center (NRWMC) located on the Ghana Atomic Energy Commission (GAEC) site in Kwabenya, a suburb of Accra. The NRWMC is the only national center mandated by regulation to receive and manage all radioactive waste in Ghana. A considerable number of radioactive sources received at the facility since its operation were without the necessary source information such as radionuclide, activity and reference date, identification number, supplier/manufacturer, etc. Sources received with information and those received without the proper information are both required to be properly characterized for the purpose of nuclear material accounting, segregation, pretreatment, conditioning and selection of appropriate management options and strategies. The risk associated with the management of disused sealed radioactive sources (DSRS) reduces considerably if the sources are conditioned. Characterization of DSRS immensely facilitates their conditioning. Radioisotopes and shield contents of DSRS stored in the Centralized Waste Processing and Storage facility of the NRWMC have been characterized. The protocol used for the characterization and the results are discussed in this paper.

The peroxicoagulation (PC) process has received great consideration for the removal of various organic contaminants. The present study investigates the landfill leachate treatment mechanism of the PC process at various pH conditions. The efficiency of the PC process was compared with that of electro Fenton (EF) and electrocoagulation (EC) processes for solutions at pH ranging from 2 to 6. ${\mathrm{Fe}}^0$, ${\mathrm{Fe}}^{2+}$, and ${\mathrm{Fe}}^{3+}$ were considered as the catalysts in the EF process and the most efficient catalyst at optimal concentration was then used for further studies. At the optimal pH, 84% of the chemical oxygen demand (COD) was removed from the leachate by the PC process, out of which 67% of COD was removed by the EF process. The COD removal efficiency of the EC process increased with an increase in solution pH. The removal of contaminants by the PC process at low pH is mainly controlled by the degradation process (EF process), and at higher pH, by the electrocoagulation process.