Journal of Hazardous, Toxic, and Radioactive Waste

Bentonite clay is a component of an engineered barrier system that is highly compacted around nuclear waste bundles in deep geological repositories (DGR). The bentonite is subject to both thermal and hydraulic gradients that may cause the barrier system to fail, compromising the stability of the deep geological repository. Regularly monitoring and assessing the condition of the highly compacted bentonite (HCB) is key to the long-term safe storage of nuclear waste bundles. The degree of saturation of the bentonite is the most critical parameter considered when assessing the performance of the material. The thermal and electrical resistivities of highly compacted bentonite samples were measured and a relationship was developed between the resistivities and the degree of saturation of the material. In addition, this study presented a relationship between total suction and electrical resistivity.

In this study, a simple and highly efficient method for stabilizing the different combinations of citric acid and sodium hydroxide on the surface of a green adsorbent was presented as the bio-originated composite for the elimination of Hg(II) and Pb(II) ions from aqueous media. The removal behavior of the green adsorbent was assessed as a function of initial pH, changing the contact time, initial pollutants concentration, temperature, cleaning process, and amount of adsorbent. The synthesized bio-originated composite was characterized using different physicochemical techniques. The metals uptake of synthesized bioadsorbent increased as a result of chemical modification, and the highest adsorption capacity [$61.54\mathrm{mg}{\mathrm{g}}^{-1}$ for Pb(II) and $45.34\mathrm{mg}{\mathrm{g}}^{-1}$ for Hg(II) ions] was achieved by citric acid (CA) and after further reaction with sodium hydroxide (NaOH) again (B─ CA─ NaOH). The sorption capacity increased in the order of $\mathrm{B}─\mathrm{CA}─\mathrm{NaOH}>\mathrm{B}─\mathrm{NaOH}─\mathrm{CA}>\mathrm{B}─\mathrm{NaOH}>\mathrm{B}─\mathrm{CA}>\mathrm{pristine}$ bone, with increasing metal concentration. The equilibrium sorption data obeyed a Langmuir–Freundlich isotherm type model. The kinetic data of the adsorption followed the mechanism of the pseudo second order model. The thermodynamic experiments indicated that the removal of metal ions was feasible, endothermic, and spontaneous. The findings of this investigation suggest that the combined modification of green adsorbent with CA and NaOH could persuade more active sites on the surface of the green adsorbent (the carboxylic acid groups of immobilized CA convert to their sodium salt form, $-{\mathrm{COO}}^{-}{\mathrm{Na}}^{+}$), which indicate very effective tendency in order to react with Pb(II) and Hg(II) ions. This study suggests that B─ CA─ NaOH has the potential to become an effective and economical adsorbent for the removal of heavy metal (HM) ions.

This paper demonstrates the utilization of the lifecycle assessment (LCA) methodology to determine the environmental burdens of steel rebar production with induction melting furnace technology. The data were obtained from an existing steel plant. The functional unit was selected as 1 t of steel rebar production. System boundaries were studied as cradle to gate. The lifecycle impact assessment analyses were considered in 11 impact categories. Analyses results summarized that the global warming potential of steel rebar production is approximately $720\mathrm{kg}{\mathrm{CO}}_2\mathrm{eq}/\mathrm{t}$ product. Electricity consumption was the major impact with effects on greenhouse gas emissions, fossil fuels–based abiotic depletion, ozone layer depletion, human toxicity, freshwater toxicity, marine aquatic ecotoxicity, terrestrial ecotoxicity, photochemical oxidation, acidification, and eutrophication. Most of the impacts of steel rebar have resulted from steel billet because the steel billet is a semifinished product of steel rebar production.

This paper presents an experimental investigation of the effect of temperature and thermal shock on the physical and mechanical properties of concrete (M25) incorporating electronic waste (E-waste). The concrete mixtures were prepared using 10, 20, 30, 40, 50% of E-waste plastic [high impact polystyrene (HIPS)] as a partial replacement per unit volume of coarse aggregate. The compressive strength, ultrasonic pulse velocity, and surface hardness of concrete specimens were examined before and after the thermal exposure. The concrete cube specimens with HIPS were heated to 100, 200, and 300°C for 1 h using muffle furnace. The compressive strength of specimens at room temperature was decreased with an increase of HIPS content. However, the specimens retained the compressive strength of about 50 at 50% HIPS replacement. Similarly, the compressive strength of specimens subjected to elevated temperatures after thermal shock decreased with an increase of HIPS and temperature. The nondestructive tests were carried out using a rebound hammer and ultrasonic pulse velocity test. The rebound hammer results provides very consistent results similar to experimental values. Regardless the temperature, concrete incorporated upto 25% HIPS showed an ultrasonic pulse velocity within the limiting value $\mathrm{3,000}\mathrm{m}/\mathrm{s}$. This study shows the feasiblility of using E-waste plastic (HIPS) in concrete as construction material in order to reduce the environmental pollution and conserve the natural resource from depletion.

A composite graphene oxide-cellulose (GOC) adsorbent was prepared from raw materials of graphite and cellulose. The structure and micromorphology of the products were characterized by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, and scanning electron microscopy (SEM). The adsorption characteristics of GOC together with graphite oxide (GO) in terms of uranium(VI) removal from aqueous solution was investigated in the batch mode reactor. The effect of solution pH, adsorbent dosage, and contact time on the adsorption characteristics of uranium(VI) was studied. Results were fitted by both the Langmuir and the Freundlich adsorption isotherms. The removal efficiency of uranium(VI) was strongly dependent on the solution pH. Graphene oxide-cellulose was used to treat a real uranium(VI)-bearing wastewater and results were promising of GOC for the management of radioactive industrial wastewater.

Due to ever increasing urbanization and industrialization, the demand for power and electricity increases at a staggering rate. In order to address the demand for electricity, more advanced and productive thermal power plants are coming up and being installed in different parts of the world. As a consequence, the generation of fly ash in large quantities as a by-product from coal-burning electric utilities has become a problem. Use of this material in construction that can consume a large volume will not only solve the disposal challenges bulk presence of fly ash, but also offers the benefit of both protecting the environment and acting as an economic alternative to traditional materials. This paper presents laboratory model tests performed on unreinforced and bamboo-geogrid reinforced fly ash walls under uniformly distributed load. The effect of the ratios of length to height (${\mathit{L}}_{\mathit{r}}/\mathit{H}$), vertical spacing to height (${\mathit{S}}_{\mathit{v}}/\mathit{H}$), and coverage (${\mathit{R}}_{\mathit{c}}$) of bamboo-geogrid reinforcement on settlement of the backfill, horizontal displacement of the facing, and failure surcharge pressure (q) was studied systematically in a series of model experiments. It was observed from the results that inclusion of bamboo geogrid (mattresses and strips) generally improved the overall behavior of the reinforced fly ash walls when compared with unreinforced fly ash walls. For example, at ${\mathit{S}}_{\mathit{v}}/\mathit{H}=0.2$ and ${\mathit{R}}_{\mathit{c}}=1$, $q$ was improved 2.47 and 3.44 times for ${\mathit{L}}_{\mathit{r}}/\mathit{H}=0.35$ and 0.65, respectively. Only doubling ${\mathit{S}}_{\mathit{v}}/\mathit{H}$ to 0.4 improved the $q$ values 1.98 and 2.81 times for ${\mathit{L}}_{\mathit{r}}/\mathit{H}=0.35$ and 0.65, respectively. Generally, increasing the length of reinforcement and coverage ratios and decreasing vertical spacing played a vital role in influencing failure surcharge pressure, backfill settlement, and lateral displacement of the facing. However, further research on a large scale or under field conditions is required for practical applications.

Electrocoagulation process efficiency to remove high concentrations of boron from surface water is studied. A glass reactor with a volume of 2.744 L installed with aluminum electrodes is used. The working parameters of initial pH (6, 7.4, 8.5, and 9); initial boron concentrations (1,998, 998, and $500\mathrm{mg}/\mathrm{L}$); and the presence of supporting electrolytes (15 mM of NaCl, ${\mathrm{Na}}_2{\mathrm{SO}}_4$, and KCl) were tested with a current density of $10\mathrm{mA}/{\mathrm{cm}}^2$ for 90 min. The optimum results were achieved with the initial pH 8.5. The removal efficiencies decreased with the increasing initial boron concentration, and the highest removal rate was measured as 55% with $500\mathrm{mg}/\mathrm{L}$ initial boron concentration. Initial boron concentration and boron removal efficiency are both found negatively correlated with the weight losses from the electrodes. As a result of principal component analysis (PCA), the presence of electrocoagulation supplying ions in the solution, the level of electric current density, and the valance of the electrolyte metal are found as the major factors influencing boron removal efficiency.

Coke oven wastewater containing high concentrations of phenol and chemical oxygen demand (COD) was collected from a local steel plant of Odisha. The treatment of coke oven wastewater was carried out by using Mobil Composition of Matter No. 41 (MCM-41) nanoadsorbent. The effect of various adsorption parameters, such as temperature (°C), initial pH, agitation speed (rpm), and MCM-41 dosage ($\mathrm{g}/\mathrm{L}$) on phenol adsorption was investigated using a two-level factorial experimental design. Enhancing MCM-41 dosage had a positive effect on the phenol adsorption performance, whereas with increasing pH, a negative effect on phenol removal was observed. The significant adsorption parameters obtained from the screening study were optimized by central composite design and response surface methodology (RSM). Results revealed that more than 96% phenol adsorption along with 90% COD removal was achieved at an optimum combination of pH 5, agitation speed 98 rpm, and $2.8\mathrm{g}/\mathrm{L}$ of MCM-41 dosage. Among the various isotherms tested at the optimized conditions, Langmuir isotherm and Temkin isotherm were found to be very well fitted to the experimental data. Furthermore, values of the dimension separation factor and interaction parameter indicated that the adsorption of phenol onto MCM-41 was very favorable. The study revealed the potential of MCM-41 for the treatment of coke oven wastewater.

A large number of children have been regularly exposed to elevated levels of vehicular emissions because of the proximity of urban schools to motorways. In this study, particulate matter (PM) concentrations were monitored in a naturally ventilated classroom located near an urban road in Chennai, India. The 24-h average suspended particulate matter (SPM), ${\mathrm{PM}}_{10}$, ${\mathrm{PM}}_{2.5}$, and ${\mathrm{PM}}_1$ concentrations in the classroom were found to be 168.64, 135.88, 42.95, and $25.89\mathrm{\mu g}/{\mathrm{m}}^3$, respectively. Chemical characterization of SPM samples indicated the dominance of organic carbon ($19.3\mathrm{\mu g}/{\mathrm{m}}^3$), ${\mathrm{SO}}_4^{2-}$ ($10.3\mathrm{\mu g}/{\mathrm{m}}^3$), elemental carbon ($6.3\mathrm{\mu g}/{\mathrm{m}}^3$), ${\mathrm{NO}}_3^{-}$ ($5.7\mathrm{\mu g}/{\mathrm{m}}^3$), ${\mathrm{NH}}_4^{+}$ ($5.6\mathrm{\mu g}/{\mathrm{m}}^3$), ${\mathrm{Na}}^{+}$ ($4.2\mathrm{\mu g}/{\mathrm{m}}^3$), ${\mathrm{Cl}}^{-}$ ($3.6\mathrm{\mu g}/{\mathrm{m}}^3$), and Ca ($3.4\mathrm{\mu g}/{\mathrm{m}}^3$) concentrations. Source apportionment of indoor SPM using the chemical mass balance model showed that soil dust (31%) was the major contributor followed by diesel exhaust (24%), secondary ammonium sulfate (13%), secondary ammonium nitrate (11%), chalk dust (7%), marine aerosols (7%), paved road dust (6%), and gasoline exhaust (1%). Health risk assessment indicated that the total hazard quotient of elements was higher than the recommended value. The total excess cancer risk was found to be four times higher than the acceptable value.

Currently, efforts are being made to increase the waste loading in vitrified waste forms for the Hanford Tank Waste Treatment and Immobilization Plant, which could result in the formation of crystalline phases within the glass. Spinel crystals that form in glass melts during vitrification of nuclear waste have a negligible impact on the performance of the glass product, and thus a melter operating with a nominal concentration of spinel crystals would be advantageous to accessing broader composition spaces and increases in waste loading. However, the total amount of crystallization must be controlled to reduce risks associated with crystal accumulation in the melter (i.e., melt properties and melter throughput/operation), and therefore a strategy to reduce the risk of failure of the melter from spinel accumulation is of interest. This study describes a method to mitigate spinel accumulation without disrupting melter operation while maintaining melt viscosity and glass product chemical durability requirements. It is found that additives can be incorporated into the glass melt that reduce the quantity of trevorite crystallization by up to 65% while maintaining acceptable viscosities for processing and chemical durabilities as measured by the product consistency test responses for disposal.