Clean Technologies and Environmental Policy

Laboratory evaluation of the mechanical properties of roller compacted concrete pavement containing ceramic and coal waste powders Abstract In this study, the use of ceramic and coal waste powders as partial replacement of cement in roller compacted concrete pavement mixture was investigated. The mixtures were produced with the ceramic waste powder contents at 5% and 10% of total cementitious material (by weight). In addition, mixtures containing ceramic and coal waste powders were prepared simultaneously. Five different concrete mixes were prepared, and the unit weight, VeBe time, compressive, splitting tensile, and flexural strengths of mixture were measured for all the specimens. All tests were performed after 7, 28, and 90 days of curing. The results indicated that the use of the ceramic and coal waste powders as a partial replacement of cement decreased the unit weight and VeBe time. According to the results, the application of ceramic and coal waste powders reduced the splitting tensile, compressive and flexural strengths than control specimens. The lowest loss in strengths was found in specimens containing 5% ceramic waste powder, that after 28-day curing, it was observed that the average compressive, splitting tensile and flexural strengths decreased by 4%, 5%, and 2%, respectively. In addition, the 28-day compressive strength of the mixture containing 5% ceramic waste powder was higher than the minimum value proposed by the guide. Furthermore, the loss of strength in specimens containing only ceramic waste powder was lower than the specimens containing ceramic and coal waste powders. It could be concluded that using ceramic and coal waste powders in roller compacted concrete pavement not only is it effective in reducing the cost and preventing waste from entering the environment but also it can be considered as a step toward sustainability. Graphical abstract

Environmental protection: reactive and proactive approaches

Green synthesis of methyl salicylate using novel sulfated iron oxide–zirconia catalyst Abstract Esters of salicylic acid are in demand for the synthesis of drugs, food preservatives, pharmaceuticals, perfumes and solvents. A novel sulfated Fe2O3–ZrO2 catalyst with different iron loadings was prepared by the combustion technique and used in the preparation of methyl salicylate from salicylic acid and dimethyl carbonate. This process is a viable and safe substitute to other esterification processes, involving harmful alkylating agents and chemicals. The activity of sulfated Fe2O3–ZrO2 was evaluated for the esterification of salicylic acid with dimethyl carbonate. No solvent was used and hence the quality of the product was excellent. The product methyl salicylate is extensively used in the food and pharma industries. Catalysts with different loadings of iron on zirconia (5, 10, 15, 20 wt.%) were synthesized, and their activities evaluated vis-à-vis ZrO2 and sulfated zirconia. The catalysts were characterized using SEM, XRD, FTIR, TGA, NH3-TPD and BET surface area analysis. The activity of the catalysts increases after the loading of iron on zirconia and 10 wt.% sulfated Fe2O3–ZrO2 gave the highest acidity and activity for the synthesis of methyl salicylate. The effect of various kinetic parameters on the rate of esterification of salicylic acid was studied. The optimum conditions for 99% conversion of salicylic acid with 100% selectivity was 120 °C after 150 min at a 1:10 molar ratio of salicylic acid to dimethyl carbonate and catalyst loading of 0.03 g/cm3. The reaction mechanism and kinetics were studied. The activation energy for this reaction was found to be 13.82 kcal/mol. Graphical Abstract

Biowaste for environmental remediation and sustainable waste management

Correction to: A review on electric vehicles and their interaction with smart grids: the case of Brazil In the original publication, the article was mistakenly published under the category “Perspective”. However, the correct category of the article is “Review”.

Comparative life cycle assessment of microalgae-mediated CO 2 capture in open raceway pond and airlift photobioreactor system Abstract A comparative life cycle assessment of CO2 capture potential of microalgae, Scenedesmus dimorphus, during autotrophic cultivation in closed airlift photobioreactor and open raceway pond under Indian conditions has been carried out. The LCA inventory inputs for the both the systems were entirely based on primary experimental data obtained by algal cultivation in 1000-L pilot-scale raceway pond and 5-L airlift photobioreactor, respectively. The primary energy demand, environmental impacts and Net CO2 capture efficiency of both the systems were evaluated. The results indicated that the primary energy demand and GWP of airlift photobioreactor were 3.7-fold higher than raceway pond. The NERCO2 (defined as net emission ratio of CO2 and estimated as ratio of CO2 sequestered/CO2 emitted) of raceway pond was fourfold higher as compared to airlift photobioreactor; however, both the cultivation systems were observed to be net negative in terms of CO2 sequestration. However, the process can become net CO2 positive, with up to fourfold and 7.5-fold enhancement in biomass productivities (wrt base value) for raceway pond and airlift photobioreactor, respectively. Further, LCA predictions indicated that utilization of energy-efficient motors with lower specific energy consumptions for microalgae cultivation would facilitate algal cultivation systems to achieve net CO2-positive sequestration.

Effect of Mn substitution on the oxidation/adsorption abilities of iron(III) oxyhydroxides Abstract In this study, divalent manganese ions [Mn(II)] were substituted a part of divalent iron ions [Fe(II)] present in Fe oxyhydroxides to prepare novel composites (Mn@Feox). The composites were prepared by (1) simultaneous hydrolysis of Fe(II) and Mn(II), and (2) rapid oxidation with H2O2. The resulting Mn@Feox prepared with different molar ratios of Fe and Mn was characterized and evaluated for their abilities to adsorb arsenic species [As(III) and As(V)] in aqueous solution. X-ray diffraction and field emission transmission electron microscope analyses revealed Mn@Feox has a δ-(Fe1−x, Mnx)OOH-like structure with their mineralogical properties resembling those of feroxyhyte (δ-FeOOH). The increase in Mn substitution in Mn@Feox enhanced the oxidative ability to oxidize As(III) to As(V), but it decreased the adsorption capacity for both arsenic species. The optimal Mn/Fe molar ratio that could endow oxidation and magnetic capabilities to the composite without significantly compromising As adsorption capability was determined to be 0.1 (0.1Mn@Feox). The adsorption of As(III) on 0.1Mn@Feox was weakly influenced by pH change while As(V) adsorption showed high dependence on pH, achieving nearly complete removal at pH < 5.7 but gradual decrease at pH > 5.7. The adsorption kinetics and isotherms of As(III) and As(V) showed good conformity to pseudo-second-order kinetics model and Freundlich model, respectively.

Ammonium removal by a novel magnetically modified excess sludge Abstract Disposal of nitrogen nutrient and excess sludge is a keen concern in wastewater treatment plants. This study describes a simple method of preparing an economical adsorbent, i.e., magnetic excess sludge (MES) by compounding the excess sludge with Fe3O4 nanoparticles. Ammonia–nitrogen removal from simulated wastewater was investigated by using the MES as an adsorbent. The MES had an adsorption efficiency of up to 90% for ammonium removal. Highly efficient separation of adsorbed ammonium on the MES could be magnetically separated from wastewater within 30 s. The operating conditions for ammonium adsorption were optimized at MES dose of 20 g/L, initial ammonium concentration of 45 mg/L and operating temperature of 298–308 K. The equilibrium data of ammonium adsorption on the MES showed a good agreement with the Langmuir isotherm, while the kinetic data were best fitted by the pseudo-second-order model. FTIR analysis indicated that various functional groups, such as hydroxyl and carboxyl groups, existed on the surface of the MES and contributed to the excellent capability for ammonium adsorption. These results suggest that the MES is a promising candidate for removing ammonium from wastewater and recycling excess sludge to ease its disposal at low cost.

Removal and recovery of phosphate anion as struvite from wastewater Abstract Phosphorus is one of the controlling factors for water eutrophication, but it is also an essential nutrient for all living organisms and non-renewable resource. A feasibility study on PO43− recovery and conversion to struvite (NH4MgPO4·6H2O), a slow-release fertilizer, has been reported. However, the fertilizer efficiency of struvite is determined by its purity, which depends on the forms and molar ratio of reactants under different initial pH of the solution. Laboratory-scale experiments were carried out to determine the optimum initial pH of the solution and molar ratio of reactants on struvite crystallization. Meanwhile, the purity of the synthesis product struvite was analyzed. The experiment results revealed the optimum initial pH being 10 with molar ratio of PO43−:Mg2+:NH4+= 1:1.3:1 and 1:2:5 for struvite formation, which the removal of the PO43−, Mg2+ and NH4+ being 98, 92, 95% and 99.5, 85, 90%, respectively. A chemical equilibrium model (Visual Minteq) corroborated the experimental results. Thus, the possibility of synthesizing struvite from simulated wastewater utilizing the phosphate ions (PO43−) was confirmed. Graphical abstract

Effect of modified shrouded intake valve on performance and emissions of spark ignition engine Abstract Strategy of lean burn for reducing fuel consumption and emissions can be achieved by incorporating swirling motion in the incoming fluid entering the cylinder of the engine. In this backdrop, the application of shrouded intake valves gets the upper hand over the conventional poppet valve because of their capacity of producing intake-generated swirl flow. In the existing literature, a modified shrouded intake valve capable of producing significant amount of swirl with relatively smaller restriction to the incoming fluid has been reported. But, no work has been done to determine the effect of using modified shrouded intake valve in the emissions and performance of an SI engine. Thus, the effect of using the modified shrouded intake valve on the emissions and performance of an SI engine is studied and compared with that of poppet intake valve and 100°, 140°, and 180° shrouded intake valves. From the study, it is seen that the engine with modified shrouded intake valve produces lowest hydrocarbon and carbon monoxide emissions for maximum power condition, whereas the brake power, brake specific fuel consumption, and NOx emissions of the engine are quite close to the engine using poppet intake valve which is the best performing valve–engine combination for the same. For minimum brake specific fuel consumption condition, the engine with modified shrouded intake valve produces the highest brake power with the lowest brake specific fuel consumption, whereas the hydrocarbon and carbon monoxide emissions of the engine are similar to the engine using 180° shrouded intake valve which is the best performing valve–engine combination for the same. Graphical abstract