Biochars, derived from rambutan (Nepheliumlappaceum) peel through slow pyrolysis, were characterised and investigated as potential adsorbent for the removal of copper ion, Cu(II) from aqueous solution. Characteristics of five biochars of rambutan peel with different pyrolytic temperatures ranging from 300 to 700 °C (B300, B400, B500, B600, B700) were studied, and adsorption abilities of respective biochars were evaluated. Adsorption experiments were carried out by varying adsorbent dosage (0.2, 0.4, 0.8, 1.0, 2.0, and 4.0 g/L) and initial copper ion, Cu(II) concentrations (50 and 100 mg/L) to determine the optimum pyrolytic temperature of biochar with high adsorption affinity. The adsorption kinetics were best described by the pseudo-second order model for all the tested biochars, while the adsorption equilibrium best fitted by Langmuir isotherm. The overall results showed that biochar derived at 600 °C can be used as an effective adsorbent for removal of Cu(II) from aqueous solutions. Furthermore, feedforward artificial neural network (FFBP) modelling was performed to compare the simulated results with experimental output data of Thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS) analysis which were trained using Levenberg-Marquardt (LM) backpropagation algorithm. The FFBP structure for pyrolysis process comprised of TGA temperature as input and biomass final weight as output. The adsorption modelling was simulated using adsorption time, temperature, biochar dosage and initial Cu(II) concentration as input data, while final Cu(II) concentration was used as output data to the network. Finally, modelling structure of 1-9-1 and 4-8-1 gave best performance with regression, R ² value of 0.9999 and 0.9547 for TGA and AAS analysis, respectively.

The anthropogenic effects of Antarctic refuge buildings and research stations on the surrounding soils are scarcely investigated, especially when the structures are small-sized, and sporadically used or visited. The Coppermine Peninsula (Robert Island, South Shetland Islands archipelago) possesses one of the richest flora in Antarctica, being classified as an Antarctic Specially Protected Area (ASPA). There, a small refuge (Luis Risopatrón) has been seasonally occupied for scientific purposes since 1957, although no studies on the anthropic disturbances in the surroundings soils are reported. The aim of this study was the determination of the potentially toxic metals (Cd, Cr, Cu, Mn, Ni, Pb, V, and Zn) mass fractions in surface soils (n = 40) collected at the surroundings of the Luis Risopatrón refuge. Enrichment factors (EF) and geoaccumulation index (I gₑₒ) were also calculated, using Zr as the reference element, in order to evaluate the anthropogenic impacts of these small buildings in the studied area. The main contaminants were Pb and Zn, which presented EF and I gₑₒ values ranging from 1.0 to 18.3 and from −1.8 to 3.5. The mass fractions of these elements determined after an aqua regia extraction varied from 5.4 to 102 mg kg⁻¹ Pb and from 43 to 210 mg kg⁻¹ Zn. These results highlight that a small refuge can show environmental disturbance from low to moderate, with few hotspots with heavily contaminated soils. Environmental monitoring strategy for similar refuges anywhere in Antarctica is recommended.

A heterogeneous photo-Fenton process was applied to treat aqueous solutions of indigo blue and textile wastewater using an iron-modified clay (Mt-Fe) and a copper-modified carbon (AC-Cu) as catalysts, the UV radiation source was the sunlight collected by a compound parabolic concentrator (CPC-2D). The treatments were conducted at pH 7.0 and 6.8 for the aqueous solutions and the textile wastewater, respectively, and different hydrogen peroxide concentrations and catalyst quantities were evaluated. The concentration of UV-A radiation collected by the CPC-2D was 54.29 ± 0.71 W/m², with an applied energy of 97.36 kJ from the concentrator device. The indigo blue removal efficiencies for Mt-Fe and AC-Cu were 98% (3 h) and 99% (1.5 h), respectively, using 1.5 g of catalyst, 0.5 M of H₂O₂, and UV radiation. The color removal efficiency in the textile wastewater was 93% after 4 h of treatment using 1.5 g of AC-Cu, 0.5 M of H₂O₂, and UV radiation. The removal of dye and color was improved by using AC-Cu and UV radiation for both systems (the aqueous solutions and the textile wastewater), showing that Cu has an important catalytic activity. IR spectra showed a change after the oxidation of organic matter by heterogeneous photo-Fenton process, and the application of the UV radiation collected by CPC-2D played an important role in the heterogeneous photo-Fenton process.

The processes of pollutant sorption by soil components control their mobility, migration, and transformation in the soil-plant system and depend on numerous properties, among which the elemental composition and surface area are dominant. In a laboratory experiment, the sorption of As and Cd by Si-rich substances differing in surface area, solubility of Si, and mineralogical composition was studied. The adsorption data were fitted to the linear, logarithmic, exponential, Langmuir, and Freundlich equations. Both size of the particles and mineral solubility of Si affected the As and Cd sorption. In the systems with lower initial concentrations of As and Cd, size of the particles had more pronounced effect on the sorption capacity. In the systems with high initial concentrations of As and Cd, the concentration of monosilicic acid was more significant than the surface area.

In this study, cassava starch wastewater was subjected to coagulation/flocculation (C/F) combined with microfiltration (MF) to improve the final quality of treated water. In the C/F tests of the effluent, the best concentration of the natural coagulant (Tanfloc POP) was determined from a statistical analysis of color removal and turbidity data. The supernatant produced in the C/F step was subjected to MF while varying the transmembrane pressure to evaluate the permeate fluxes, fouling mechanism, and permeate quality. The mathematical model that best represented the filtration process was the fouling mechanism of partial membrane pore blockage. The best experimental conditions for coagulant dosage, settling time, and MF pressure in the combined C/F-MF process were 320 mg L⁻¹, 15 min, and 1.4 bar, respectively. The highest overall removal efficiency rates achieved were 99% color, 91% cyanide, 75% total organic carbon, and 100% turbidity, demonstrating the promising potential of the combined C/F-MF process in the treatment of cassava starch wastewater.

The aim of the study was to determine the changes in suspension particle size identified in biologically treated wastewater, which was then treated in hydroponic system with use of engineering lighting by the light-emitting diodes (LED). The study was subjected to wastewater purified under laboratory conditions, in a hydroponic system using the effect of macrophytes Pistia stratiotes and growing algae. Measurement of particle size was made using a laser granulometer. Analysis of the results showed that the additional lighting of the hydroponic system with LED can significantly influence the ability of the suspension particles to agglomerate and, consequently, determine their sedimentation properties. In hydroponic system supported by additional lighting, more particles were observed with equivalent diameter D(3.2) smaller than 10 μm than those in the tank without additional lighting, indicating a higher reactivity of the particles. Determining the size of equivalent diameters D(4.3) allowed us to observe that in hydroponic system, particles of relatively small size predominate, which negatively affects the sedimentation process of the suspensions. Determination of particle size of suspensions consisting mainly of algae and the dynamics of their changes are the basis for specification of an effective method of removing particles from the system to protect the receiver from excessive suspension concentrations.

A dispersive liquid–liquid microextraction (DLLME) method was optimized for the detection of chlorobenzene (CB) compounds in the drying process of municipal and dyeing sludge. Compared with traditional methods, the optimized DLLME not only has a lower limit of detection but also saves analysis time and requires less amount of organic solvent. Using this method in analyzing CB release during sludge drying, we found that drying temperature is the main factor controlling the amount of chlorobenzene release during sludge drying. In addition, we found that most CBs were released when sludge drying entered into the second falling rate stage, i.e., a period when sludge moisture content was low and temperature was high. By analyzing organic matter content in association with CB release during sludge drying, the relationship between organic matter transformation and chlorobenzene release was established. The results provide scientific basis and technical support for assessing the risks of the secondary pollution of CBs from sludge drying.

Elevated radium (Ra) concentrations have been observed in aquifers with high naturally occurring salinity. The flux of radon (Rn) gas from the decay of Ra out of saline aquifers can be enhanced owing to salting-out effects. This raises the issue as to whether increased salinization of groundwater from road deicing practices can enhance Ra and Rn mobility to the extent that they become a human health concern. Continued use of salt (NaCl) as a road deicing agent has resulted in a gradual salinization of groundwater systems in snow-affected regions. This study presents groundwater data from a monitoring well field installed around a permeable pavement parking lot at the University of Connecticut, Storrs campus. The data suggest a connection between road salting and (a) the mobilization of dissolved Ra as well as (b) enhanced Rn gas flux from the water table. A positive correlation (R ² = 0.92) was identified between dissolved Na⁺ and isotopes of Ra; a negative relationship was observed between specific conductance and dissolved Rn. In two monitoring locations, concentrations of Ra were detected that exceeded the EPA MCL of 5 pCi/L. Concentrations of Rn in the groundwater were found to be at a level that theoretically could generate gas concentrations in the vadose zone that exceed the indoor Rn standard by orders of magnitude. Given these findings, it appears that salt contamination of groundwater could increase the potential for human exposure to these radioactive and carcinogenic elements. Graphical Abstract Photo of the study area taken 1/14/16

Electrocoagulation (EC) technology is an attractive alternative for industrial wastewater treatment due to its simplicity, low operation cost, less sludge production, less chemical addition, and larger and more stable floc formation. The main objective of this research is to investigate the effect of using powdered residuals from water purification plants (PRWPP) on dye removal efficiency and energy consumption under various operational conditions (pH, initial dye concentration, and applied voltage) in order to enhance the EC performance. A series of laboratory-scale experiments were conducted using an EC bench-scale reactor with iron electrodes. The addition of PRWPP to the EC system increases the dye removal efficiency from 32.9 to 97.2% and decreases the energy consumption from 6.08 to 2.06 kWh/kg dye removed. The highest dye removal efficiency was achieved at a PRWPP dosage of 2 g/l, an applied voltage of 5 V, and an initial pH value ranging from 6 to 9. The higher the dye influent concentrations discharged to EC, the lower the removal efficiency achieved and current efficiency. PRWPP has a beneficial effect on the EC performance in terms of the dye removal efficiency as well as the energy consumption.

The study is a first-time investigation into the use of Eucalyptus leaves as a low-cost herbal adsorbent for the removal of arsenic (As) and mercury (Hg) from aqueous solutions. The adsorption capacity and efficiency were studied under various operating conditions within the framework of response surface methodology (RSM) by implementing a four-factor, five-level Box–Wilson central composite design (CCD). A pH range of 3–9, contact time (t) of 5–90 min, initial heavy metal (As or Hg) concentration (C ₀) of 0.5–3.875 mg/L, and adsorbent dose (m) of 0.5–2.5 g/L were studied for the optimization and modeling of the process. The adsorption mechanism and the relevant characteristic parameters were investigated by four two-parameter (Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich) isotherm models and four kinetic models (Lagergren’s pseudo-first order (PFO), Ho and McKay’s pseudo-second order (PSO), Weber–Morris intraparticle diffusion, and modified Freundlich). The new nonlinear regression-based empirical equations, which were derived within the scope of the study, showed that it might be possible to obtain a removal efficiency for As and Hg above 94% at the optimum conditions of the present process-related variables (pH = 6.0, t = 47.5 min, C ₀ = 2.75 mg/L, and m = 1.5 mg/L). Based on the Langmuir isotherm model, the maximum adsorption or uptake capacity of As and Hg was determined as 84.03 and 129.87 mg/g, respectively. The results of the kinetic modeling indicated that the adsorption kinetics of As and Hg were very well described by Lagergren’s PFO kinetic model (R ² = 0.978) and the modified Freundlich kinetic model (R ² = 0.984), respectively. The findings of this study clearly concluded that the Persian Eucalyptus leaves demonstrated a higher performance compared to several other reported adsorbents used for the removal of heavy metals from the aqueous environment.