Journal of Hazardous, Toxic, and Radioactive Waste

A face-centered central composite design was applied as an input to the artificial neural network (ANN), demonstrating the significance of statistical design for an efficient performance with a lesser number of data. The influence of the initial fluoride concentration, adsorbent dose, and reaction time on the fluoride adsorption capacity of the calcined $\mathrm{Ca}\text{-}\mathrm{Al}\text{-}({\mathrm{NO}}_3)$ layered double hydroxide was determined through the response surface methodology (RSM) and ANN. A significant variation of the adsorption capacity ($3.17–22.16\mathrm{mg}/\mathrm{g}$) confirmed the importance of the selected process parameters. The adsorption capacity was found to be increased with the increase in the initial fluoride concentration, whereas a reverse trend was observed with the variation of the adsorbent dose. A significant interactive effect was found between the adsorbent dose and the initial fluoride concentration. The mean square of error and ${\mathit{R}}^2$ associated with the RSM and ANN model are 0.139, 0.135 and 0.993, 0.995, respectively. The several error functions and linear regression among the predicted and experimental values of the ANN and RSM model demonstrated a better applicability of the ANN model.

The major limitations of the Fenton process are the working pH range (2–5) and the high cost of ${\mathrm{H}}_2{\mathrm{O}}_2$. These limitations were unraveled using the ${\mathrm{Fe}}^{2+}$-air oxidation process, in which ferrous ions were used with continuous aeration without ${\mathrm{H}}_2{\mathrm{O}}_2$ at a higher pH (pH = 10). This paper studies the effect of the initial hydrous ferric oxide (HFO) concentration on the ${\mathrm{Fe}}^{2+}$-air process. The enhancement in degradation of the dye [Reactive Black 5 (RB5)] was observed using the ${\mathrm{Fe}}^{2+}\text{-}\mathrm{air}$ process in the presence of initial HFO, as compared to the ${\mathrm{Fe}}^{2+}$-air process in the absence of initial HFO. The enhancement is possibly attributable to the adsorption of ferrous ions, dye, and oxygen onto the HFO surface and leading to effective utilization of reactive oxidizing species. The oxidizing entities appear to be generated during oxidation of adsorbed ferrous ions under oxic conditions—probably on the surface of HFO. Furthermore, the ${\mathrm{Fe}}^{2+}$-air process in the presence of HFO reduces the concentration of ferrous ions required for decolorization of RB5 compared to the ${\mathrm{Fe}}^{2+}$-air process without HFO and hence resulting in an overall-economical process for the pretreatment or degradation of recalcitrant compounds.

This paper provides a first review of the contamination level of emerging contaminants (ECs) in aquatic sources of India. Contaminants reported so far belong to pesticides, pharmaceuticals, personal care products (PCPs), surfactants, and phthalates. A total of 41 publications are reported with a maximum share of pesticides (57%) followed by pharmaceuticals (17%), surfactants (15%), PCPs (7%), and phthalates (5%). The concentration of detected contaminants in all aquatic sources range as not detected (ND) to $\mathrm{10,000}\mathrm{ng}/\mathrm{L}$ (pesticides), ND to $14\times {10}^6\mathrm{ng}/\mathrm{L}$ (pharmaceuticals), ND to $\mathrm{5,160}\mathrm{ng}/\mathrm{L}$ (PCPs), $1.3\times {10}^6$ to $6.2\times {10}^6\mathrm{ng}/\mathrm{L}$ (surfactants), and ND to $0.2\times {10}^6\mathrm{ng}/\mathrm{L}$ (phthalates). In surface water and treated wastewater, the maximum concentration of pesticides exceed their prescribed environmental quality standards. Pharmaceuticals such as cetirizine, ciprofloxacin, and citalopram are present up to $2.1\times {10}^6\mathrm{ng}/\mathrm{L}$, $14\times {10}^6\mathrm{ng}/\mathrm{L}$, and $0.4\times {10}^6\mathrm{ng}/\mathrm{L}$, respectively, in treated wastewater, which is the highest measured concentration. A higher risk (hazards $\text{quotient}>1$) to aquatic organisms in surface water has been reported for PCPs, surfactants, and phthalates. The review can act as a framework to nurture future research and regulatory initiatives for monitoring of ECs in remaining aquatic sources.

This work aimed to find inexpensive alternatives that could serve both as carbon source and biofilm carrier for heterotrophic denitrification in treating nitrate contaminated waters. To ascertain cost efficiency, the effectiveness of four different waste organic solid substances (WOSS) like sugarcane bagasse (SB), coconut shell (CS), aegle shell (AS), groundnut shell (GS), and the equal-volume mixture of all (Mix) were assessed in batch experiments. Subsequently, the best performing (Mix) substrate was evaluated in column mode of experiments under different experimental conditions and the optimized values were verified as bed depth of 30–40 cm, hydraulic retention time (HRT) of 24–26 h, and flow rate of $1.5\mathrm{mL}/\min$. In optimum conditions, real domestic wastewater was successfully denitrified over a period of 2 months. The first-order reaction with $R^2$ in the range of 0.96–0.99 better described the denitrification process both in batch and column studies. Mix substrate further contributed to a speedy establishment of active denitrifying consortia consisting of Stenotrophomonas, Bacillus, and Ochrobactrum as the dominant genuses. The study validated the possible application of the selected Mix substrate as a potential substrate for biological denitrification process.

A byproduct of the steel industry, basic oxygen furnace slag (BOFS) is used to remove As(III) from groundwater, and its adsorption efficiency is compared with commercially available zero-valent iron (ZVI). Batch experiments were performed to determine their feasibility as adsorbents and to investigate different experimental parameters such as adsorption kinetics, adsorption isotherms, anionic effects, and desorption. Field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscope (HR-TEM), and X-ray diffraction (XRD) were used to characterize particle size, the surface morphology of pristine materials and As(III)-treated products. As(III) adsorption kinetics occurred on a scale of hours following a pseudo-first-order rate constants ($k_{\mathrm{obs}}$) $0.15–0.85{\min }^{-1}$ and $0.080–0.52{\mathrm{h}}^{-1}$ (at varied adsorbents concentration) of BOFS and ZVI, respectively. The As(III) adsorption affinity by BOFS and ZVI were 0.96 and $1.2\mathrm{mg}\mathrm{As}(\mathrm{III}){\mathrm{g}}^{-1}$ of adsorbents at $1\mathrm{mg}{\mathrm{L}}^{-1}$ As(III) initial concentration, 15°C, which was calculated using Langmuir isotherm, respectively. Interestingly, there was no interference of bicarbonate (${\mathrm{HCO}}_3^{-}$) for both BOFS and ZVI, whereas an increase in anions (${\mathrm{H}}_4{\mathrm{SiO}}_4^0$ and ${\mathrm{H}}_2{\mathrm{PO}}_4^{2-}$) up to 100 mM for As(III) adsorption on BOFS decreased the As(II) adsorption on ZVI and BOFS to 1 and 14–23%, respectively. There was no desorption of arsenic while desorbing with deionized water. However, in the presence of phosphate (100 mM), there was $\sim 20$ and 18% desorption for BOFS and ZVI, respectively. This study shows that BOFS has great potential for in situ remediation, which is $\sim 20$ times cheaper and highly efficient than ZVI for arsenic removal from aqueous solution.

This study narrates the use of postconsumer waste plastic water bottles for developing a new type of encasement to confine fly-ash columns fully penetrated in soft clay. Geocell-reinforced fly-ash beds along with a jute geotextile separator were also placed over the fly-ash columns, while the cellular mattresses were also made of the same type of plastic water bottles. A series of systematic model tests were carried out on encased fly-ash columns, geocell composite systems, and encased fly-ash column–geocell composite systems in soft clay, while the three different systems produced improved footing capacity of about 5-fold, 8.5 times, and 12-fold, respectively, as compared to the untreated clay bed. It was observed that with the increase in mattress height over the encased fly-ash column, the contribution from the encased column decreased accompanying the higher contribution from the geocell mattress in the overall footing capacity over the encased fly-ash column–geocell composite systems. Moreover, model tests were performed on groups of three and four end-bearing encased fly-ash columns in triangular and square patterns, respectively, to determine the efficacy of the proposed plastic bottle encasement in a group column situation. The group of four columns showed better footing capacity than that over single columns and the group of three columns.

The disposal of toxic substances on land imposes adverse effects to the surrounding lithospheric environment. Suitable low cost and sustainable locally available materials are very much needed for attenuation of migratory pollutants through lithospheric media. Natural clay and fine-grained soils are widely used as primary liner material in containment and tailing pond structures because of their economic superiority, sustainability, and favorable removal capacity. An investigation was carried out to examine the potential capacity of two fine-grained soils (Type S1) and (Type S2) for attenuating phenolic migration through subsurface environment. Statistically designed experiments based on the central composite method (CCD) was used to describe the interacting effects of four independent variables such as initial phenol concentrations ($3–15\mathrm{mg}/\mathrm{L}$), soil mass amount ($4–20\mathrm{g}$), solution pH (4–10), and the nature of adsorbent (S1) and (S2) on the uptake of phenol. The CCD along with $\alpha$ (distance of each axial point) equal to 1.316 and six central points were used to develop the second-order mathematical model using the experimental results that were obtained through 40 batch test data. The significance of different independent variables and their influence on the phenol removal percentage was also identified by ANOVA. A desirability function was further introduced to optimize the process parameters. The results showed that soil type (S1) would be more suitable for removal of phenol (43.54%) and the optimum values of initial phenol concentrations, soil dose, and pH were $15\mathrm{mg}/\mathrm{L}$, $5.74\mathrm{g}/100\mathrm{mL}$, and 6.95, respectively, with a desirability value of 0.886.

Compacted bentonites are frequently used as a clay liner material at landfill because of their high specific surface area (SSA), high cation exchange capacity (CEC), contaminant adsorption capacity, and low hydraulic conductivity. The heavy-metal contaminants present in the leachates of the wastes affects the pore-fluid chemistry and diffuse double layer (DDL) thickness of the clay particles. The heavy-metal contaminants suppress the DDL thickness of bentonite, resulting in a decrease in its swelling capacity. Consolidation is one of the important behaviors of bentonite, which is required to be investigated for settlement calculation of landfill liner. This investigation was performed to study the effect of different heavy-metal contaminants of varying concentration on the consolidation characteristics of bentonite. Two bentonites with different liquid limit and swelling capacity were studied for change in their various consolidation parameters such as coefficient of volume change ($m_v$), coefficient of consolidation ($c_v$), compression index ($C_c$), and time requires for the completion of 90% of consolidation ($t_{90}$) in the presence of zinc, lead, and copper contaminants at a concentration of 100 and $\mathrm{1,000}\mathrm{mg}/\mathrm{L}$. The results showed that the $C_c$, $m_v$, and $t_{90}$ of the bentonites decreased, whereas $c_v$ increased with the increase in heavy-metal contaminants concentration. Higher-quality bentonite, defined by a higher swelling capacity, exhibited a higher $C_c$, $m_v$, and $t_{90}$ than those of the lower-swelling bentonite. The results showed that the $c_v$ of the samples decreases and the $t_{90}$ increases with an increase in consolidation pressure. Because bentonite is widely used as a liner material in landfills, the results of this study may provide a general guideline for estimating the liner performance in the presence of different kinds of contaminants and thus help in choosing the bentonite type for the liner application.

In this research, a novel activated biomass was prepared from Caryota urens based on sulphuric acid treatment (surface-modified Caryota urens seeds, SMCUS) followed by ultrasonication (ultrasonic-assisted Caryota urens seeds, UACUS). The prepared material was effectively applied to treat a cadmium-contaminated water system. The novel synthesized material was analyzed by scanning electron microscopic (SEM) and Fourier transform infrared (FTIR) spectroscopic analyses. Adsorption experiments were conducted to check the adsorption-influencing parameters, including contact time, initial cadmium concentration, temperature, and system pH. Adsorption isotherm and kinetics for cadmium removal by adsorbents were studied systematically. Adsorption equilibrium data were explained by three, four, and five parameter isotherm models at different temperatures. The kinetics for cadmium adsorption was explained by pseudo-first-, and pseudo-second-order models and also by Elovich models at different temperatures. The Langmuir adsorption capacity of UACUS was calculated as $183.4\mathrm{mg}/\mathrm{g}$. Cadmium adsorption by adsorbents has been well described in the literature and by pseudo-first-order models. Cadmium adsorption was decreased with increased temperature (30–60°C). This confirms that the present adsorption system is exothermic in nature. Thermodynamic factors include $\mathrm{\Delta }\mathrm{G}°$, $\mathrm{\Delta }\mathrm{H}°$, and $\mathrm{\Delta }\mathrm{S}°<0$, showed that cadmium adsorption is spontaneous, exothermic, and enthalpy driven, respectively. The decrease in $\mathrm{\Delta }\mathrm{G}°$ values with the increase in temperature from 30 to 60°C states that more adsorption sites exist at lower temperature

Improper disposal of effluents from bulk drug manufacturing units creates a pathway for antibiotics to enter the aquatic environment. This study investigated the presence and distribution of antibiotics belonging to fluoroquinolone group (ciprofloxacin, lomefloxacin, ofloxacin, norflaxacin, enrofloxacin, pefloxacin, and difloxacin) in the aquatic environment of the Musi River in India. Results showed that fluoroquinolones were present in exceptionally high concentrations in the river. Ciprofloxacin, ofloxacin, and norfloxacin were frequently detected with the highest concentrations, up to 5,015, 542.4, and $251\mathrm{\mu g}/\mathrm{L}$, respectively. Due to the impact of effluents from bulk drug manufacturing units, antibiotic concentration was observed to be several folds higher than the usual range of its occurrence around the world. Positive correlation was observed between the concentration of fluoroquinolones in the water and sediment samples collected along the river due to sorption affinity of fluoroquinolones onto solids. The findings from the present study call for an increased focus on the development of regulatory specification and safe disposal practices of bulk drug manufacturing units into surface water.

Layered double hydroxides (LDHs) are usually synthesized by a conventional coprecipitation using inorganic salts. In this study, waste serpentine tailings (WSTs), including MgO and ${\mathrm{Fe}}_2{\mathrm{O}}_3$ with contents of 34 and 4.27%, were used to prepare Mg(II)Fe(III) LDHs. Firstly, WSTs were leached in a nitric acid solution at 90°C using a refluxing process in the presence of a $\text{solid}:\text{liquid}$ ratio of $1:4$. By a countercurrent leaching process, the acidity of the leaching solution not only was decreased but Mg and Fe were also enriched. Subsequently, waste iron was put into the leaching solution, which was used to adjust molar ratio of magnesium to ferrum. Finally, 30% NaOH solution was slowly put into the described solution to synthesize Mg(II)Fe(III)LDHs. The structure and surface morphology of the LDHs were characterized by an X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed typical structure of Mg(II)Fe(III) brucitelike sheets with exchangeable capability in an interlayer space. This study indicated that it was feasible to synthesize Mg(II)Fe(III) LDHs using WSTs and waste iron.

In this study, the electronic waste (e-waste) from PVC cable outer casing was used as fiber in concrete. Fiber-reinforced concrete was made using e-waste fibers of aspect ratio 35 that were incorporated into the concrete at 0.6, 0.8, and 1%, respectively, with respect to the weight of the cement. Silica powder was added to the fiber-reinforced concrete to make silica fiber reinforced concrete by 10% of a volume of the cement. The shear strength of the e-waste fiber reinforced concrete and e-waste with silica powder fiber-reinforced concrete was studied, and the test results were compared with the normal concrete. The addition of silica powder added to the fiber-reinforced concrete improves the shear strength as compared to the shear strength of fiber-reinforced concrete. The shear strength value of fiber-reinforced concrete was reduced to 25.6%, and silica fiber-reinforced concrete was reduced to 21.5% with respect to the normal concrete shear capacity at maximum 1% addition of fiber. Even though the reduction in strength was observed, the e-waste fibers considerably reduced the brittle behavior of the normal concrete. Thus, the use of e-waste fiber in concrete will help to reduce the solid waste management problem and provide for the new fiber material in future research areas of concrete.