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Summary Flocculation is a mainstream technology for the provision of safe drinking water but is limited due to the ineffectiveness of conventional flocculants in removing trace low-molecular-weight emerging contaminants. We described a synthesis strategy for the development of high-performance nanoflocculants (hydrophobic-organic-chain-modified metal hydroxides [HOC-M]), imitating surfactant-assembling nano-micelles, by integration of long hydrophobic chains with traditional inorganic metal (Fe/Al/Ti)-based flocculants. The core-shell nanostructure was highly stable in acidic stock solution and transformed to meso-scale coagulation nuclei in real surface water. In both jar and continuous-flow tests, HOC-M was superior over conventional flocculants in removing many contaminants (turbidity, UV254, and DOC: >95%; TP and NO3-N: >90%; trace pharmaceuticals [initial concentration: 100 ng/L]: >80%), producing flocs with better structural and dewatering properties, and lowering the environmental risk of metal leaching. The rationally designed nanoflocculants have large application potential, as a solution to increasing public concern about micro-pollutants and increasing water quality requirements., Graphical abstract, Highlights • Hydrophobic-organic-chain-modified metal hydroxide (HOC-M) flocculants are designed. • HOC-M removes various contaminants in a single step from river water. • HOC-M produced flocs with better structural and dewatering properties. • Nano-structure transformation promotes formation of meso-scale coagulation nuclei., Environmental chemical engineering ; Surface chemistry; Environmental science; Environmental chemistry; Water resources engineering

Summary The bio-based lactic acid (LA) and the common metal ion chelating agent iminodiacetic acid (IDA) are used to design and prepare a polymeric sustained-release Pb2+ chelating agent by a brief one-step reaction. After the analysis on theoretical calculation for this reaction, poly(lactic acid-iminodiacetic acid) [P(LA-co-IDA)] with different monomer molar feed ratios is synthesized via direct melt polycondensation. P(LA-co-IDA) mainly has star-shaped structure, and some of them have two-core or three-core structure. Thus, a possible mechanism of the polymerization is proposed. The degradation rate of P(LA-co-IDA)s can reach 70% in 4 weeks. The change of IDA release rate is consistent with the trend of the degradation rate, and the good Pb2+ chelating performance is confirmed. P(LA-co-IDA) is expected to be developed as a lead poisoning treatment drug or Pb2+ adsorbent in the environment with long-lasting effect, and this research provides a new strategy for the development of such drugs., Graphical abstract, Highlights • Novel bio-based polymeric Pb2+ chelating agent is first developed from lactic acid • The star-shaped structure and properties of P(LA-co-IDA) can be controlled by DMP • The products can be sustainably degraded and released to chelate Pb2+ as designed • Tunable Pb2+ chelating capacity is suitable for drug in lead poisoning treatment, Environmental chemistry; Environmental Chemical Engineering; Chemical reactions in materials science.

Summary Catechol is speculated to be a potential precursor of environmentally persistent free radicals (EPFRs) in the atmosphere. EPFRs absorbed on PM2.5 have attracted public attention because their toxicity is similar to cigarette smoke. In this study, we found that catechol could produce EPFRs, which were oxygen-centered phenoxy and semiquinone radicals. These free radical species had half-lives of up to 382 days. CaO, CuO, and Fe2O3 markedly promoted EPFR formation from catechol. The valence states of Cu and Fe changed during the photochemical reactions of catechol but no valence state changed for Ca. Alkaline nature of CaO is possibly the key for promoting the free radical formations through acid-base reactions with catechol. In addition to hydroxyl free radicals, hydrogen free radicals and superoxide anions formed from the photochemical reactions of catechol were first discovered. This is of concern because of the adverse effects of these free radicals on human health., Graphical abstract, Highlights • Photochemical mechanism of persistent free radicals from catechol was clarified • Significant free radicals were formed via photochemical reactions of catechol • •H and O2•− were first discovered from the photochemical reactions of catechol • This study is important for better recognizing DNA damage of air inhalation of PM2.5, Chemistry; Environmental Chemical Engineering; Theoretical Photochemistry; Environmental Science

Summary There is no efficient wastewater treatment solution for removing organic micropollutants (OMPs), which, therefore, are continuously introduced to the Earth's surface waters. This creates a severe risk to aquatic ecosystems and human health. In emerging water treatment processes based on ion-exchange membranes (IEM), transport of OMPs through membranes remains unknown. We performed a comprehensive investigation of the OMP transport through a single IEM under non-steady-state conditions. For the first time, positron annihilation lifetime spectroscopy was used to study differences in the free volume element radius between anion- and cation-exchange membranes, and between their thicknesses. The dynamic diffusion-adsorption model was used to calculate the adsorption and diffusion coefficients of OMPs. Remarkably, diffusion coefficients increased with the membrane thickness, where its surface resistance was more evident in thinner membranes. Presented results will contribute to the improved design of next-generation IEMs with higher selectivity toward multiple types of organic compounds., Graphical Abstract, Highlights • Electroneutrality overcomes diffusive potential of charged OMPs • The interactions between OMPs and the IEMs determine OMP transport • Adsorption influences diffusion lag time of neutral OMPs • Diffusion coefficients of neutral OMPs increased with IEMs thickness, Chemistry; environmental chemical engineering; environmental science; chemical engineering

Summary Oxidative water purification of micropollutants (MPs) can proceed via toxic intermediates calling for procedures for connecting degrading chemical mixtures to evolving toxicity. Herein, we introduce a method for projecting evolving toxicity onto composite changing pollutant and intermediate concentrations illustrated through the TAML/H2O2 mineralization of the common drug and MP, propranolol. The approach consists of identifying the key intermediates along the decomposition pathway (UPLC/GCMS/NMR/UV-Vis), determining for each by simulation and experiment the rate constants for both catalytic and noncatalytic oxidations and converting the resulting predicted concentration versus time profiles to evolving composite toxicity exemplified using zebrafish lethality data. For propranolol, toxicity grows substantially from the outset, even after propranolol is undetectable, echoing that intermediate chemical and toxicity behaviors are key elements of the environmental safety of MP degradation processes. As TAML/H2O2 mimics mechanistically the main steps of peroxidase catalytic cycles, the findings may be relevant to propranolol degradation in environmental waters., Graphical Abstract, Highlights • TAML(s) catalyzed H2O2 mineralization of persistent micropollutant propranolol • Major intermediates kinetically characterized for catalytic and noncatalytic reactions • Method introduced quantifying evolving composition and toxicity of process solution • Toxicity grew after complete propranolol removal—toxicity data gap highlighted, Chemical Engineering; Environmental Chemical Engineering; Green Chemistry; Environmental Chemistry

Modified polyvinyl alcohol (PVA) beads serve as effective anaerobic microbe immobilization carriers. PVA beads were mixed with different conductive materials, activated carbon, magnetite, and green tuff stone powder. In this study, modified PVA beads were used to investigate the effect of using, promote methane production, and enhance direct interspecies electron transfer (DIET) on the anaerobic syntrophic degradation of propionate, which is an essential intermediate process for generating methane in anaerobic digesters. The batch experiment showed that PVA mixed with activated carbon had the highest methane conversion rate of 72%, whereas the rates for control (sludge) was 61%. Moreover, the lag time during the second and third feedings was shorter by 5-fold than for the first feeding when modified PVA beads were added. The syntrophic propionate degrading microorganisms in the modified PVA beads was Syntrophobacter and Methanobacterium, either Methanoculleus or Methanosaeta. The modified PVA beads hold at least 10 times larger syntrophs than normal PVA. Therefore, composite PVA with conductive materials can promote methane production, accelerate propionate consumption, and enhance electron transfer in related microbial species., Energy; Chemical engineering; Environmental science; Environmental chemical engineering; Environmental engineering; Environmental management; Environmental pollution; Conductive materials; Direct interspecies electron transfer; Methane production, Polyvinyl alcohol bead; Syntrophic propionate degradation

Abattoir wastewater generated from various meat processing operations in several developing countries pose a serious threat to the environment. Consequently, there is urgent need to reduce the impact of environmental pollution from it. Coagulation techniques have been recommended and used by many researchers successfully in treating wastewater, therefore an investigation of possible use of chito-protein extracted from crab shell (locally sourced) was used as a coagulant for treating abattoir wastewater. Coagulation experiments were carried out using jar-test procedure to investigate the influence of pH, time of settling, temperature and adsorbent dosage for coagulation of BOD, COD, Turbidity and Colour from the wastewater sample. To determine the interaction effect of the various process variables, Response Surface Method (RSM) was used in the optimization of the process variables. To determine the effectiveness of the coagulant, pre and post characterization of the wastewater samples were undertaken, the result of the post characterization of the wastewater sample indicated that most of the water quality parameters except Iron were within WHO standard. The Total Suspended Solid (TSS), for instance stood at 564.6 mg/L and 29 mg/L respectively for pre and post characterisation, the value of 29 mg/L of the post characterization was below the WHO recommended value of 30 mg/L. The predicted responses and the experimental values correlated significantly, an indicator that RSM optimization method used in this study is suitable in modelling the process variables. The result of the study further shows that optimum process variable is dependent on the solution pH (acidic), coagulant dosage of 2–3g, settling time of 25–30 min and operating temperature from 323K to 333K. The coagulant used in this study, when compared with previous studies have shown to have strong potential for use as a coagulant and as an alternative to chemical coagulants in the treatment of abattoir wastewater., Chemical engineering; Environmental science; Environmental engineering; Waste treatment; Environmental chemical engineering; Water pollution; Wastewater management; Crab shell; Abattoir wastewater treatment; Chito-protein; RSM optimization; Coagulation

Air pollutant data are compositional in character because they describe quantitatively the parts of a whole (atmospheric composition). However, it is common to use air pollutant concentrations in statistical models without considering this characteristic of the data and, therefore, without control of common statistical problems, such as spurious correlations and subcompositional incoherence. This paper now proposes a daily multivariate spatio-temporal model with a compositional approach. The air pollution spatio-temporal model is based on a dynamic linear modelling framework with Bayesian inference. The novel modelling methodology was applied in an urban area for carbon monoxide (CO, mg·m−3), sulfur dioxide (SO2, μg·m−3), ozone (O3, μg·m−3), nitrogen dioxide (NO2, μg·m−3), and particulate matter less than 2.5 μm in aerodynamic diameter (PM2.5, μg·m−3). The proposal complemented and improved the conventional approach in air pollution modelling. The main improvements come from a fast multivariate data description, high spatial-correlation, and adequate modelling of air pollutants with high variability., Statistics; Engineering; Atmospheric science; Environmental analysis; Environmental chemical engineering; Environmental impact assessment; Compositional data; CoDa; Air quality; Environmental statistics; Modelling

The study assessed the impacts of abattoir activities on ambient air quality and health risk associated with exposure to PM2.5 and PM10, H2S, SO2 and NH3. Air samplings were done simultaneously around the abattoir at three points for sixty consecutive days (October to November) and standard methods adopted for the samplings and analysis. Health risks associated with exposure to PM10 and PM2.5 were estimated, using attributable fractions, relative risk and the excess lifetime cancer risk. The non-carcinogenic risks induced by the inhalation of H2S, SO2 and NH3 were also evaluated using hazard quotient (HQ). The results indicated that the average concentrations of 18.75 μg/m3, 89.17 μg/m3 and 0.1ppm for PM2.5, PM10 and NO2 respectively, were higher than the World Health Organization (WHO), National Ambient Air Quality Standard (NAAQS) and Federal Ministry of Environment (FMEnv) permissible limits. Air Quality Index showed that the ambient air quality in respect of CO and NH3 was very good, moderate for PM10 and was very poor for NO2 and SO2. It was also shown that 0.32% of deaths from lung cancer, and 0.23% from cardiopulmonary could be avoided if PM2.5 is reduced to 3 μg/m3 and while about 0.14% of all-cause mortality could be avoided if PM10 is reduced to 10 μg/m3. In similar manner, at least 0.45% likelihood that an individual in a group of people exposed to PM2.5 100m away from the burning point may have health issue (lung cancer) than an individual from another set of people that is exposed to baseline concentration of 3 μg/m3. All the HQ values exceeded the threshold value, set at the unity, implying that H2S, SO2 and NH3 are likely to cause adverse health effects in the area. Conclusively, continuous operation of this abattoir within the residential area can constitute a great environmental menace to the residents of the area and can result in complication to those with existing health challenge., Abattoir; Air quality; Particulate matter (PM); Air quality index; Dispersion; Cancer, Environmental chemical engineering; Atmospheric chemistry; Environmental analysis; Environmental health; Environmental impact assessment; Environmental risk assessment, Environmental science, Chemistry, Chemical engineering.

Summary It is still challenging to develop strongly alkali-resistant catalysts for selective catalytic reduction of NOx with NH3. It is generally believed that the maintenance of acidity is the most important factor because of neutral effects of alkali. This work discovers that the redox properties rather than acidity play decisive roles in improving alkali resistance of some specific catalyst systems. K-poisoned Fe-decorated SO42−-modified CeZr oxide (Fe/SO42−/CeZr) catalysts show decreased acidity but reserve the high redox properties. The higher reactivity of NHx species induced by K poisoning compensates for the decreased amount of adsorbed NHx, leading to a desired reaction efficiency between adsorbed NHx and nitrate species. This study provides a unique perspective in designing an alkali-resistant deNOx catalyst via improving redox properties and activating the reactivities of NHx species rather than routinely increasing acidic sites for NHx adsorption, which is of significance for academic interests and practical applications.

The amount of palm oil mill residues increases rapidly and will become a severe problem in the future. One potential technique for alleviating this concerning environmental problem is to convert these residues into biochar by the pyrolysis process. Pyrolysis of three types of palm oil mill residues (namely, palm kernel shells, empty palm fruit bunches, and oil palm fibers) was conducted in a fixed bed reactor at 500 °C and 2 L/min of nitrogen flow rate for 60 min. The optimization of biochar production was performed using the Box-Behnken design and analyzed using response surface methodology. The effects of three potential factors, including pyrolysis temperatures, nitrogen flow rates, and biomass particle sizes, were studied. The results showed that the highest biochar yield (44.91 wt%) was obtained from pyrolysis of palm kernel shells at 525 °C with a nitrogen flow rate of 2 L/min and a particle size of 750 μm. Application of biochar produced from palm kernel shells for carbon dioxide capture was tested in a packed bed adsorber of 3.0 g of biochar sample by flowing 1,400 ppm of carbon dioxide in the gas feed mixture at 2.5 L/min. The capacity of the biochar sample for CO2 adsorption was 0.46 mmol/g., Chemical engineering; Environmental chemical engineering; Materials characterization; Adsorption; Biochar; Pyrolysis; Palm oil; CO2; RSM.

Solidifiers are dry, granular hydrophobic polymers that form physical bonds with hydrocarbons by molecular interactions (hydrogen bonding, London forces), and are used to immobilize hydrocarbon spill propagation and dispersion. CIAgent© is a non-toxic, proprietary polymer blend listed as an “Oil Solidifier” on the EPA's National Contingency Plan Product Schedule for use on hydrocarbon spills in the navigable waterways of United States. CIAgent solidifies the liquid hydrocarbons through a rapid transformation into a cohesive rubber-like inert mass upon contact and retains the liquid for easier removal and disposal. The objective of this paper is to determine the effectiveness of the solidifier with a variety of hydrocarbon liquids that could be encountered in an oil spill scenario. The effectiveness of the solidifier was characterized in terms of the application rate, temperature change, solubility parameters and solidification time for a variety of hydrocarbon liquids (e. g., gasoline, diesel fuel, crude oil) that could be encountered by measuring the heat of solidification using a solution calorimeter. A thermogram was obtained and the heat of solidification was calculated using the temperature difference upon solidification. The temperature change and the degree of swelling in the solidifier were used to determine the solubility parameter of the solidifier (6.77 Hildebrands). The heat of solidification value was used to determine the ease and speed of the solidification of the hydrocarbon liquids. Solidification times ranged from 40 to 120 s for the liquids tested. The average application ratio in weight of solidifier to weight of hydrocarbon ranged was 3.35., Chemical engineering; Environmental Chemical Engineering; Transport Process; Adsorption; Water Treatment; Environmental Hazard; Solidification; Hydrocarbon; calorimeter; polymer; spill remediation

Microbubble technology dramatically raises the efficiency of the flotation and aeration processes of water treatment plants (WTPs), which see extensive use in developed countries. A local institution, Indonesia Water Institute, has tried to investigate microbubble technology intended for lab-scale WTP. However, the current reactor system does not yet meet the microbubble criteria, especially as it has had few investigations of its abilities in flotation and aeration. This study aims to analyze the effect of size variations that affect the rising velocity and mass transfer coefficient (kLa) of aeration contact time. Three local spargers were used to produce microbubbles. Bubble diameters were measured optically and analyzed using ImageJ software. The dissolved oxygen (DO) concentration was measured every minute using an automated sensor so that the kLa could be determined. Of the three spargers, the smallest bubble size was produced by the vortex type with an average bubble diameter of 89 μm and the slowest rising velocity of 17.67 m/h. It also yielded the highest kLa of 0.297/min, which gave an aeration contact time of 3.64 minutes. The experimental uses of three local spargers revealed that the smaller the microbubble diameter, the higher the mass transfer coefficient in flotation and aeration processes. This research can be the basis for developing microbubble technology for WTP in Indonesia., Chemical Engineering; Environmental Science; Water Treatment; Green Engineering; Environmental Chemical Engineering; Water Pollution; Aeration; Flotation; mass transfer coefficient; Microbubble; rising velocity.

Iron chelate liquid redox sulfur recovery (LRSR) has been one of the most frequently recommended technologies for the oxidation of H2S in natural gas into elemental sulfur, particularly when the acid gas has a high CO2/H2S molar ratio. The process is however known to suffer from extensive oxidative ligand degradation that results in high operational costs. Moreover, poor biodegradability or toxicity of the existing ligand has become a concern. In this research, we demonstrated that gluconate, a naturally greener ligand, when coupled with manganese as the metal, has considerable potential to be a better redox agent. Manganese gluconate solution was more resistant against ligand degradation compared with iron NTA. As required, aerated solution was capable of converting dissolved NaHS into elemental sulfur. At sufficiently high pH, manganese gluconate solutions were stable enough from precipitation of manganese hydroxide, carbonate, or sulfides. An equilibrium calculation has been developed to understand the precipitation behavior., Chemical engineering; Environmental chemical engineering; Industrial chemistry; Environmental chemistry; Environmental hazard; Manganese gluconate; Sulfur recovery; Liquid redox; Natural gas; Acid gas; Elemental sulfur

In Ecuador, the net energy contribution of biofuels is unknown or unnoticed. To address this issue, we determined the Energy Return on Investment (EROI) for bioethanol and biodiesel. The selection of raw materials relied on their productive capacity, export and import records, and historical yields. Consequently, the scope included three raw materials for ethanol (sugar cane, corn, and forest residues) and four for biodiesel (African palm, pinion, bovine fat, and swine fat). Using a method based on the Life Cycle Analysis (LCA) of each biofuel, we assessed the entire production chain through statistical processing of primary and secondary information. Then we calculated the calorific values in the laboratory, compared energy inputs/outputs, and finally obtained the energetic returns. EROIs for bioethanol were: 1.797 for sugarcane, 1.040 for corn, and 0.739 for wood. The results for biodiesel were: 3.052 for African palm, 2.743 for pinion, 2.187 for bovine fat, and 2.891 for swine fat. These values suggest feasibility only for sugarcane in the case of ethanol. In contrast, biodiesel has better prospects because all the feedstocks analyzed had EROIs higher than two. Nevertheless, biodiesel is not available for trading in Ecuador because energy policy has overlooked systems based on higher energy return. Future studies should consider more comprehensive variables such as climate change, land use, and water management., Energy; Environmental chemical engineering; Biofuel; Energy economics; Energy sustainability; Energy return of investment; Life cycle analysis; Transport sector; Ecuador.

Water purification is indispensable to guarantee safe human consumption and to prevent diseases caused by the ingestion of contaminated water. This requires a series of water treatment processes which require investment. However, the economic limitations of rural communities hinder their ability to implement such water-treatment systems, as is the case in Ciénaga Grande of Santa Marta (“Large Swamp”, in English) in Colombia. Low-cost systems can be used instead as simple and safe alternatives. Therefore, the objective of this work was to evaluate non-conventional, low-cost water processes to purify the water from the collection point of two stilt house villages in Ciénaga Grande of Santa Marta. These include: 1) Using two natural coagulants, Moringa Oleifera and Cassia Fistula; 2) filtration through a biosand filter and a carbon activated filter; and 3) disinfection through UV-C Radiation and through solar disinfection. The results showed a turbidity values reduction between 52% and 96% using the two natural coagulants; both turbidity and total coliforms achieved reductions of 98.4% and 76.9%, respectively in the filtration process; and removal of total coliforms up to 98.8% in the disinfection process. Despite the high rates of reduction in the different parameters, the water does not comply with the recommended limits for safe drinking water., Water treatment; Green engineering; Environmental chemical engineering; Environmental health; Public health; Ciénaga Grande of Santa Marta, Low-cost water purification, Stilt house villages, Non-conventional treatment

[EN] This study presents an analysis of three models associated with artificial intelligence as tools to forecast the generation of urban solid waste in the city of Bogota, in order to learn about this type of waste's behavior. The analysis was carried out in such a manner that different efficient alternatives are presented. In this paper, a possible decision-making strategy was explored and implemented to plan and design technologies for the stages of collection, transport and final disposal of waste in cities, while taking into account their particular characteristics. The first model used to analyze data was the decision tree which employed machine learning as a non-parametric algorithm that models data separation limitations based on the learning decision rules on the input characteristics of the model. Support vector machines were the second method implemented as a forecasting model. The primary advantage of support vector machines is their proper adjustment to data despite its variable nature or when faced with problems with a small amount of training data. Lastly, recurrent neural network models to forecast data were implemented, which yielded positive results. Their architectural design is useful in exploring temporal correlations among the same. Distribution by collection zone in the city, socio-economic stratification, population, and quantity of solid waste generated in a determined period of time were factors considered in the analysis of this forecast. The results found that support vector machines are the most appropriate model for this type of analysis., This work was supported by the Santo Tomas University.

A bench-scale model of a partially packed upflow anaerobic fixed film (UAF) reactor was set up and operated at five different hydraulic retention times (HRTs) of (17, 14, 10, 8, and 5) days. The reactor was fed with synthetic rubber wastewater consisting of a chemical oxygen demand (COD) concentration of 6355–6735 mg/L. The results were analyzed using the Monod model, the Modified Stover-Kincannon models, and the Grau Second-Order Model. The Grau Second-Order model was found to best fit the experimental data. The biokinetic constant values, namely the growth yield coefficient (Y) and the endogenous coefficient (Kd) were 0.027 g VSS/g COD and 0.1705 d−1, respectively. The half-saturation constant (Ks) and maximum substrate utilization rate (K) returned values of 84.1 mg/L and 0.371 d−1, respectively, whereas the maximum specific growth rate of the microorganism (μmax) was 0.011 d−1. The constants, Umax and KB, of the Stover-Kincannon model produced values of 6.57 g/L/d and 6.31 g/L/d, respectively. Meanwhile, the average second-order substrate removal rate, ks(2), was 105 d−1. These models gave high correlation coefficients with the value of R2 = 80–99% and these indicated that these models can be used in designing UAF reactor consequently predicting the behaviour of the reactor., Chemical engineering; Environmental chemical engineering; Biofuel; Water treatment; Environmental engineering; Waste treatment; Anaerobic digestion; Upflow anaerobic fixed film (UAF); Monod; Stover-Kincannon; Grau second-order

The reaction kinetic rate and mass transport play an important role in the sizing and scale-up of reactors. The Damköhler's dimensionless number (Da) is the quotient of these effects. A new interpretation of Da as a local property is introduced Da(x,y,z,t). A new graphical methodology is proposed for the sizing and scale-up of unidirectional flow reactors and CSTRs. The partial differential equation (PDE) and algebraic that describe the continuity within these reactors transform into dimensionless variables, and the conversion at the output is expressed as a function of the conditions at the input Da0. The operating conditions as volumetric flow, residence time; design variables as reactor volume; and intrinsic reaction rate are involved in Da0. The equations are solved numerically to develop the design charts Da0 vs X. The design volume is linear with Da0, and the conversion is obtained from the charts (Da0 vs X) or vice versa. Using these charts avoids the analytical or numerical solution of the PDE that governs the unidirectional flow reactors becoming an easy tool for scale-up. The article portrays how to use these diagrams. Reactors with Da0< 0.1 have a low conversion per pass, the charts also allow estimating the number of recirculations required as a function of the overall conversion. Reactors with the same conversion have the same Da0, both laboratory and industrial scale. Then, the Danumber is presented as a fundamental parameter for design and scaling-up these reactors., Chemical engineering; Catalyst; Environmental chemical engineering; Chemical reaction engineering; Computer-aided engineering; Scale-up; Reactor design; Reaction engineering; Modeling; Kinetic rate.

Lead is a heavy metal that is bio accumulative and non-biodegradable that poses a threat to our health when it exists in excess in our bloodstream. It has found its way into wastewater from mostly chemical industrial processes. In this article, we investigated the adsorption and hence removal of lead (II) ions from wastewater in order to purify it for re-use in industrial processes or for plant and animal use. We synthesized nano silica hollow spheres (NSHS) and used them as adsorbents to remove lead ions from wastewater. When we characterized the NSHS using X-Ray diffraction, the amorphous nature of silica was evident with average crystal size of 39.5 nm. Scanning electron microscopy was used to determine the morphology of the adsorbent and the particles were found to be spherical in shape within a size range of 100–200 nm. Thermogravimetric analysis was used to determine the mass loss of NSHS which was ~2% at 800 °C. Our experimental results from adsorption studies showed that there was a linear relationship between temperature (27–60 °C) and adsorption efficiency and an inverse relationship between initial metal concentration (50–300 mg/L) and adsorption efficiency. At a maximum temperature of 60 °C and maximum initial metal concentration of 300 mg/L, the adsorption capacity was 200 mg/g and 262 mg/g, respectively while the adsorption efficiency was 99.6% and 87.4%, respectively. Our equilibrium and thermodynamic results revealed that the process was better modelled by the Langmuir adsorption isotherm (qmax = 266.89 mg/g and b = 0.89 L/mg). The adsorption process was both endothermic (ΔH = 97 kJ/mol) and spontaneous (ΔG = -22 kJ/mol). We can conclude that we were able to successfully synthesize NSHS, use them to remove lead (II) ions and the produced NSHS have a capacity that is higher than most other adsorbents investigated by other researchers., Chemical Engineering; Environmental Science; Physical chemistry; Environmental Chemical Engineering; Adsorption; Surface Chemistry; Environmental Pollution; Nano sodium silicate hollow spheres; equilibrium studies; Freundlich isotherm; Langmuir isotherm; thermodynamic studies; Wastewater; lead ions.

The increase in price of the available refined petroleum products for local consumption in Nigeria had led to the emergence of indigenous technology for petroleum refining in some parts of the Niger Delta region. This study, therefore characterized and quantified artisanal refineries’ gaseous emissions for possible air pollutants based on various unit operations involved and evaluated their impacts. It measured the emissions directly from source using E8500 Portable Combustion Analyzer. It also categorized oven sizes/processing capacity of the refineries into various ranges in order to estimate emissions according to processing capacity. The result revealed that; pollutants emission varied significantly between the unit operations and increased with increase in processing capacity. When the emissions were compared with daily limits set by the Environmental Guidelines and Standard for Petroleum Industry in Nigeria (EGASPIN) 2002, the emissions (CO, NOx, and SO2) breached the available set limits. While with the Federal Environmental Protection Agency (FEPA), 1991 set limits for emissions from stationary source; HC and CO breached their limits. SO2 and H2S breached their lower limits but were below the upper limit, while NOx emissions were found within its set limit. The study concluded that, Nigeria Artisanal Petroleum Refineries are sources of air pollution, as they impact the host environment., Environmental science; Chemical engineering; Environmental chemical engineering; Atmosphere modelling; Air quality; Environmental chemistry; Environmental hazard; Environmental pollution; Artisanal refineries; Characterisation; Air pollutants; Crude oil; Niger-Delta.

The present work provides to treat real oily saline wastewater released from drilling oil sites by the use of electrocoagulation technique. Aluminum tubes were utilized as electrodes in a concentric manner to minimize the concentrations of 113400 mg TDS/L, 65623 mg TSS/L, and the ions of 477 mg HCO3/L, 102000 mg Cl/L and 5600 mg Ca/L presented in real oily wastewater under the effect of the operational parameters (the applied current and reaction time) by making use of the central composite rotatable design. The final concentrations of TDS, TSS, HCO3, Cl, and Ca that obtained were 93555 ppm (17.50%), 11011 ppm (83.22%), 189ppm (60.38%), 80000ppm (22%), and 4200 ppm (25%), respectively, under the optimum values of the operational parameters (1.625 Amps and 40 min). In spite of the low removal percentages of some pollutants, the present study proved the ability of this novel designed reactor for treating high saline real oily wastewater in accordance with the operational parameters. This prove the capability of the use of it as a pre-treatment of other conventional methods., Chemical engineering; Environmental chemical engineering; Chemical reaction engineering; Electrochemical engineering; Adsorption; Water treatment; Real oily saline wastewater; TDS; TSS; HCO3; CL; Ca; Electrocoagulation reactor; Optimization.

Summary Excessive phosphorus in water is the primary culprit for eutrophication, which causes approximately $2.2 billion annual economic loss in the United States. This study demonstrates a phosphate-selective sustainable method by adopting Garcinia subelliptica leaves as a natural bio-template, where MgMn-layered double hydroxide (MgMn-LDH) and graphene oxide (GO) can be grown in situ to obtain L-GO/MgMn-LDH. After calcination, the composite shows a hierarchical porous structure and selective recognition of phosphate, which achieves significantly high and recyclable selective phosphate adsorption capacity and desorption rate of 244.08 mg-P g−1 and 85.8%, respectively. The detail variation of LDHs during calcination has been observed via in situ transmission electron microscope (TEM). Moreover, the roles in facilitating phosphate adsorption and antimicrobial ability of chemical constituents in Garcinia subelliptica leaves, biflavonoids, and triterpenoids have been investigated. These results indicate the proposed bio-templated adsorbent is practical and eco-friendly for phosphorus sustainability in commercial wastewater treatment., Graphical Abstract, Highlights • A natural bio-template provides hierarchical porous structure • The variation of nanostructure during thermal process is discussed in detail • The composite shows high sorption, selectivity, stability, and sustainability, Environmental Chemical Engineering; Green Chemistry; Natural Material

Suzuki Indomobil Motor Plant (SIMP) Cakung, East Jakarta, Indonesia generates wastewater containing heavy metals such as nickel, zinc, chromium, copper, and COD derived from the metal coating process using the electroplating system. Electroplating wastewater produced by this company contains Nickel and COD above the quality standards set by the Government of DKI Jakarta (Governor Regulation No. 69/2013). This research aims to analyze and compare the efficiency and kinetics of Nickel complexes and COD removal using the Advanced Oxidation Process (AOP) and Electrocoagulation (EC) method. Electroplating wastewater generated by SIMP Cakung (ratio of plating wastewater to overflow plating wastewater is 1:30) in this study had characteristics of 379–568 ppm (effluent standard = 75 ppm) of COD, and 87.555–121 ppm (effluent standard = 1 ppm) of Nickel. Preliminary experiments with the factorial design method indicated that independent variables (pH, current density, ozone flow rate, and contact time) had a critical influence/significance on the removal efficiency of Nickel complexes, while the influence of the above variables in COD removal efficiency was not significant. Optimum operating conditions for Nickel complexes and COD removal using both AOP and EC reactor were found in this study as well as the reaction kinetics of the removal rate. Our study found that the optimum operating conditions for Nickel complexes and COD removal using the AOP reactor were at the pH of 10, the ozone flow rate of 2 L/min, the contact time of 60 min (99.75% and 51.25% for Nickel and COD removal, respectively). For the EC reactor, the optimum condition for Nickel and COD removal are pH of 6.5, the current density of 20 mA/cm2 and the contact time of 50 min (99.75% and 51.25% for Nickel and COD removal, respectively). In these conditions, the AOP reactor in its optimum condition could remove Nickel and COD more compared to the EC reactor. This finding suggests that AOP technology is not only reliable in removing Nickel from electroplating industrial wastewater, but also it could reduce the loading of COD for further treatment units by more than 50%. Further studies in the effect of the longer contact time and higher ozone flowrate on COD removal is suggested., Environmental chemical engineering; Waste treatment; Waste; Wastewater management; Electroplating wastewater; Wastewater treatment; Advanced oxidation process; Electrocoagulation.

In this study, a Methyl Green (MG) dye pollutant was separated by Mobil Composition Matter No. 41 (MCM-41) in a fixed-bed continuous column with investigated three parameters, namely a bed height (2–6 cm), initial MG concentration (10–30 mgL-1) and a process flow rate (0.8–1.6 mL min−1). Results indicated that the highest bed capacity of 20.97 mg/g was obtained with respective to optimal values such as; 6 cm for a column height, 0.8 mL min−1 for flow rate, and an initial MG concentration 20 mgL-1. Furthermore, a quantity of the adsorbed pollutant decreased as the flow rate increased, while increasing the initial MG concentration yielded the opposite effect. The column apparatus was performed properly at the low flow rate, whereas both the breakthrough and exhaustion time increased with the bed depth. Thomas and Yoon-Nelson models were applied for predicting the breakthrough curves and calculating the characteristic factors of the laboratory fixed-bed adsorption column, which were beneficial for process design. Based on regression coefficient analyses, results of employing the Yoon-Nelson model was found to be superior to the Thomas one. Breakthrough performance indicated that MCM-41 was suitable for applications in continuous adsorption regimes for MG dye. The mesoporous MCM-41 was recovered effectively by calcinations and employed again for four times in the continuous system successfully., Chemical engineering; Environmental science; Industrial engineering; Environmental engineering; Waste treatment; Water treatment; Environmental chemical engineering; Separation; Fixed bed adsorption; Methyl green; MCM-41; Wastewater treatment.

Sites contaminated by Dense Non-Aqueous Liquid Phases (DNAPLs) containing chlorinated compounds are a ubiquitous problem caused by spills or the dumping of wastes with no concern for the environment. Their migration by gravity through the subsurface and their accumulation far below ground level make in-situ treatments the most appropriate remediation technologies. In this work, an aqueous solution containing a non-ionic and biodegradable surfactant was injected in the Sardas alluvial layer contaminated at some points with DNAPL (formed by a mixture of more than 28 chlorinated compounds) from lindane production. A volume of 5.28 m3 of an aqueous surfactant emulsion (13 g L−1) was injected at 14.5 m b g.l in the permeable layer (gravel-sand), at a flow rate of 0.6 m3 h−1 and the groundwater was monitored within a test cell (3.5 m radius) built ad hoc. The flow of the injected fluids in the subsurface was also evaluated using a conservative tracer, bromide (130 mg L−1), added to the surfactant solution. Concentration of contaminants, chloride, bromide and surfactant, surface tension and conductivity were measured at the injection point and at three monitoring points over time. High radial dispersion was noticed resulting in high dilution of the injected fluids. The surfactant was not adsorbed in the soil during the injection time, the adsorption of the surfactant took place in the meantime (15 h) between its injection and the groundwater (GW) extraction. The concentration of chlorinated compounds dissolved from the soil in the surfactant aqueous phase when equilibrium was reached (about 850 mg L−1) is related to the moderate average contamination of the soil in the test cell (about 1230 mg kg−1). In contrast, the extraction of the free DNAPL in the altered marls layer was highly enhanced due to the addition of the surfactant. Finally, it was found that the surfactant and the contamination did not migrate from the capture zone., Chemical engineering; Environmental chemical engineering; Soil pollution; Environmental pollution; Contaminant transport; Lindane wastes; DNAPL; Surfactant; Alluvium; Tracer; Landfill

Bioelectrochemical systems (BES) application was proposed for a variety of specific uses, due to these systems’ characteristics: electrodes can act as virtually inexhaustible electron acceptors/donors, offering a growth-support surface for microorganisms, and stimulating naturally-occurring microbial degradation activities. In situ, groundwater denitrification therefore seems to be a potential candidate for their use. In this study, buried biocathodes were operated in laboratory settings for the simulation of in situ groundwater denitrification. Two alternative configurations were tested: biocathode buried in sand, and biocathode buried in gravel. A control test with a biocathode in absence of sand/gravel was also performed. In all the cases, biocathodes were driven by power supply or potentiostat to guarantee a steady electron flux to the cathode. The presence of sand and gravel strongly influenced the denitrification process: in both configurations, accumulation of intermediate N-forms was detected, suggesting that the denitrification process was only partially achieved. In addition, a significant decrease (in the 20–36% range) in nitrate removal rates was measured in sand and gravel setups compared to the control reactor; this issue could be attributed to lack of recirculation that limited contact between substrate and electrode-adherent biofilm. Biocathodes buried in gravel obtained better results than those buried in sand due to the lower packing of the medium. The results of this study suggest that, in order to achieve successful in situ treatment, special design of submerged-biocathodic BESs is necessary.