Batch adsorption studies for cadmium (Cd), copper (Cu) and chromium (Cr) onto an agricultural soil impacted by mining activities were conducted in single- and multi-component systems. The effect of initial concentration, pH and competing ions (Fe³⁺, Ca²⁺, Co²⁺, Mg²⁺, K⁺, Ni²⁺ and Zn²⁺) on adsorption was studied. The soil exhibited high adsorption capacities for the elements at all initial concentrations with the adsorption process better described by the Freundlich isotherm. Adsorption was found to proceed via an ion exchange mechanism. The pseudo second-order kinetic model described the adsorption of the elements (R ² > 0.999), indicating a chemisorption process. The adsorption of Cd increased with pH in both systems while that for Cu decreased. The adsorption of Cr decreased with pH in the single-component system, but increased in the multi-component system. The adsorption of Cd was affected more by competing ions while Cu and Cr were not significantly affected (p > 0.05). Elemental speciation under varying conditions was studied using the PHREEQC geochemical modelling code. The observed high capacity of the soil for the elements pointed to the soil’s potential as a repository, a feature that would change depending on the speciation of the elements and soil conditions.

Surface modification of the silica nanoparticles was performed using trithiocyanuric acid (TCA-SNPs) so as to enhance the adsorption of Ag⁺ from aqueous solutions. The surface modification to the adsorbent was characterized by Fourier transform infrared spectroscopy, transmission electron microscope, and X-ray photoelectron spectroscopy. The Ag⁺ adsorption capacity was found to increase with increase in the solution pH, with the optimal pH being 5.0. The Ag⁺ adsorption isotherm was generated at 25 °C at the optimal solution pH and the maximum adsorption capacity was found to be 80 mg/g, significantly higher than the adsorption capacity reported for other adsorbents in literature. The increase in adsorption capacity was attributed to the presence of thiol groups on the surface of the modified adsorbents. Additionally, the adsorption kinetics was estimated at 25 °C, which indicated very high rates of adsorption initially, with rapid reduction in rate of adsorption with time. Both adsorption isotherms as well as the adsorption kinetics were modeled with popular models. The adsorption isotherm was found to match with the Langmuir model while the adsorption kinetics was found to match with the pseudo-second-order kinetic model. The adsorption-desorption cycles indicate the TCA-SNPs to be stable adsorption performance and retain high adsorption efficiency ensuring commercial adoption. A relatively low adsorption of other ions such as Mn²⁺, Cu²⁺, Ni²⁺, Co³⁺ as compared to Ag⁺ was ensured.

Water quality assessment typically includes the determination of chemical oxygen demand (COD) by oxidation of organic matter with Cr(VI) in an acidic medium followed by digestion. Unfortunately, the required reagents are harmful and the reaction times are rather long. We investigated earlier the use of H₂O₂ as a more environmentally friendly oxidizing agent to replace the hazardous chromates. In the present study, we have furthered this possibility by incorporating the use of H₂O₂ in the presence of UV light. A protocol has been devised and tested with standards and real samples that replaces toxic Cr(VI), halves the amount of silver sulfate required, and greatly reduces the necessary reaction time, thus yielding a faster and more environmentally sound method.

Graphene oxide (GO) and graphene oxide modified with methyl-β-cyclodextrin denoted as GO-mβCD were prepared and applied as adsorbents to determine the adsorption characteristics of Pb(II) from aqueous solutions. The characteristic results of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) showed that mβCD was successfully physically attached to GO to form the GO-mβCD nanocomposite. The adsorption equilibrium and kinetics of the adsorbents were well described by Langmuir isotherm and pseudo-second-order models, respectively. The maximum Pb(II) adsorption capacity of GO-mβCD (at pH = 6 and room temperature) was determined as 312.5 mg/g which was significantly higher than that of GO (217.39 mg/g). This indicates that the modification of GO with mβCD enhances the adsorption capacity of GO. The desorption studies show that the adsorbent GO-mβCD can be used for at least five cycles with non-significant loss of its initial adsorption capacity for Pb(II) ions.

This article investigates the impact of five determinants of the green supply chain practices on organizational performance in the context of Pakistan manufacturing firms. A sample of 218 firms was collected from the manufacturing industry. The green supply chain practices were measured through five independent variables including green manufacturing, green purchasing, green information systems, cooperation with customers, and eco-design. By using exploratory factor and simultaneous regression analysis, the results indicate that except green purchasing, rests of the four independent variables have been found statistically significant to predict organizational performance. However, the eco-design of green practices followed by green information systems has revealed the greatest impact on organizational performance. Therefore, the managers of the manufacturing firms should not only implement eco-design in their supply chain but also concentrate on proper monitoring and implementation of green information systems to increase their firms’ performance. A main contribution of this research from theoretical side is that it is possible to notice a negative effect of “green purchasing” towards organizational performance particularly in the scenario of Pakistan manufacturing industry. Another valuable result is that green purchasing is an important antecedent of firms economic performance in the US manufacturing firms (Green et al. 2012), although not significantly related to organizational performance in our study. In addition, we also discussed research limitations, areas for future research, and implications for practitioners.

Hydrophilic carbonaceous nanoparticles (HNPs) of uniform sizes with a good degree of dispersion in water were produced from a commercial carbon black by nitric acid treatment. The surface treatment, performed at different reaction times, generates a variable number of oxygen functional groups, mainly carboxylic, which enhance the nanoparticles hydrophilicity and heavy metal adsorption capability. The HNPs were characterized by a number of analytical techniques, including FTIR spectroscopy, thermal and elemental analysis, N₂ adsorption, dynamic light scattering, and zeta-potential measurements. The acid–base properties of the functional groups on the HNPs surface were also investigated by coulometric–potentiometric titrations. Cadmium adsorption tests were carried out in stirred reactors containing colloidal aqueous suspensions of HNPs and HNPs supported over silica. The effects of several parameters, such as the cadmium concentration, the temperature, and the solution pH, were studied. Sorbents showed an appreciable cadmium adsorption capability at different temperatures and in a wide range of pH values comparable or superior to several carbon-based sorbents, indicating a feasible use in commercial units.

This work studies the degradation of safranin T (SF, a recalcitrant pollutant) by an electrochemical process and three photochemical advanced oxidation technologies (TiO₂ photocatalysis, UV/H₂O₂, and photo-Fenton). The degradation routes of each process were elucidated initially. Based on the mineralization extent, improvement of the treated solutions’ biodegradability, and energy consumption, the most suitable process was identified. Interestingly, in the electrochemical system, safranin T was efficiently eliminated through electrogenerated HOCl. In contrast, the popular photo-Fenton process was unable to degrade SF. Moreover, the pollutant was refractory to highly energetic UV₂₅₄ irradiation. Meanwhile, the UV/H₂O₂ and TiO₂ photocatalysis processes removed SF slowly. Interestingly, the electrochemical system produced biodegradable solutions. Furthermore, the electrical energy consumption (EC) for the 100% removal of SF showed that the electrochemical process only spent 0.04 and 0.06% of the EC needed by TiO₂ photocatalysis and UV/H₂O₂, respectively. Therefore, the fast SF degradation, the high biodegradability intensification, and the very low energy consumption evidenced the relative advantages of the electrochemical process for the remediation of water containing safranin T. Finally, to obtain a deeper understanding of SF degradation by the electrochemical system, an analysis of structural transformations was made. It was found that the electrogenerated HOCl initially attacked the central azine and the aromatic amines on SF. Subsequently, aliphatic compounds were formed, which due to their biodegradable character could be completely eliminated by a conventional biological system or discharged into natural media.

Economic and environmental stimuli for biodiesel production have also increased production of glycerol, a byproduct present in biodiesel industry wastewater (BIW). The objective of the present study was to analyze which factors influenced glycerol biodegradation in anaerobic sequencing batch reactors (AnSBR) in the attempt to optimize chemical oxygen demand (COD) removal efficiency. Six factors were analyzed: pH, temperature, mixing speed, influent COD, inoculum mass, and reaction time. The results indicated that mixing speed, temperature, mass of inoculum, and reaction time had direct influence on COD removal efficiency in BIW. The reactor used in the experiments operated with efficiencies and applied loads above those mentioned in the literature. The mathematical model generated in this study can be used for estimating efficiency, process control and scale up of AnSBR.

To meet demand for processes that minimize the environmental impact generated by waste, efficient systems that degrade such substances and use them as an alternative source for renewable energy generation are increasingly becoming needed. Increased food production to meet the needs of the world’s increasing population has encouraged the use of agrochemicals in order to ensure productivity in crops. However, excessive use of pesticides has caused contamination of natural systems and, therefore, of living beings. In this context, this work presents an alternative plan for an integrated system that simultaneously remediates contaminated environments and generates electricity using a Cu/CuO electrode as a photocatalyst. The materials were prepared from reagents and accessible metals, which reduced costs and contributed to a clean process, without using organic additives. The results showed that the generation of current in an area 6.9 cm² was 193.37 μA for potassium hydrogen phthalate degradation. The Aminol 806® and Connect® pesticides were degraded by 54.46 and 21.02%, respectively, after 90 min in the system, under ultraviolet radiation. The results showed that, at pH 2.0, the generation of current was 2493.2 mA (36.165 mA m⁻²) for Aminol 806® and 7.894 mA (0.114 mA m⁻²) for Connect®. The degradation of organic contaminants and simultaneous power generation of energy in the integrated system provides a self-sustaining form of environmental remediation and energy recovery, and its use is possible on a large scale.

Combustion of fossil fuels has contributed to many environmental problems including acid deposition. The Clean Air Act (CAA) was created to reduce ecological problems by cutting emissions of sulfur and nitrogen. Reduced emissions and rainfall concentrations of acidic ions have been observed since the enactment of the CAA, but soils continue to receive some acid inputs. Many soils sensitive to acid deposition are found to have low pH, a loss of base cations, and a shift in the mineral phase controlling the activity of Al³⁺ and/or SO₄²⁻. If inputs continue, soil may be depleted of base cations and saturated with Al and could cause low forest productivity. Soil samples and soil solutions from pan lysimeters were taken on ridge-tops in the Daniel Boone National Forest to evaluate potential impacts of acid deposition recently and in the future. Sample results were compared to historical data from identical locations. Physicochemical characteristics of the soils revealed that sites were very low in base saturation and pH and high in exchangeable acidity, illustrating change since previously sampled. Soil solution data indicated that sites periodically received high acid inputs leading to saturation of Al in soils and the formation of Al-hydroxy-sulfate minerals. Given these conditions, long-term changes in soil chemistry from acid deposition are acknowledged.