The work aims to study the removal of crystal violet (CV) using laterite soil with surface modification by surfactant (SML). Surface modification of laterite soil was conducted by pre-adsorption of sodium dodecyl sulfate (SDS) at pH 4 and low ionic strength to enhance removal of CV. The effective conditions for CV removal through adsorption technique using SML were optimized and found to be contact time 60 min, pH 6, adsorbent dosage 5 mg/mL, and 5 mM NaCl as background electrolyte. The highest removal of CV using SML reached to 86.5% under optimum conditions. We used Fourier transform infrared spectroscopy (FT-IR) to evaluate the change of surface vibrational groups of laterite after SDS pre-adsorption and after CV adsorption while the different charged surface was determined by ζ potential measurements. The CV adsorption onto SML increased when increasing ionic strength from 1 to 10 mM. Nevertheless, at high ionic strength, this trend is reversal due to desorption of SDS from laterite surfaces. Adsorption isotherms of CV onto SML at different NaCl concentrations were tried to fit by Langmuir, Freundlich, and a two-step adsorption models. The adsorption kinetics were in good agreement with pseudo-second-order model. The removal efficiency of CV after four regenerations still reached higher than 85%. On the basis of adsorption isotherms, charged surface change by ζ potential and surface modification by FT-IR, we suggest that CV adsorption onto SML was induced by both non-electrostatic and electrostatic interactions. We also demonstrate that SML is a novel, reusable, and low-cost adsorbent for cationic dye removal from aqueous solution.

The applications of photocatalytic processes have been explored, and their ability as microbial disinfection has been recognized. This review article will introduce the related parameters in semiconducting oxide photocatalyst applications as a photocatalytic microbial disinfection in order to provide better understanding on achieving excellent performance in photocatalytic disinfection. Several significant parameters have been identified, namely, pH, catalyst loading, particle size, temperature, inorganic ions, doping, light intensity, and irradiation time. This mini review may be useful for directing the photocatalyst research under the visible light region for microbial disinfection.

Waste stabilization ponds (WSP) used to treat dairy shed effluent hold significant loads of recoverable nutrients in the sludge. Land application of this pond sludge over grazing paddocks is a potential alternative to chemical fertilizer. Desludging of WSPs can further enhance the nutrient removal efficiency of the WSP and thereby improve the water quality of the WSP effluent and limit accumulation of phosphorus (P) in WSPs. The aim of this study was to investigate the changes in the nutrient content of soil after land application of pond sludge (PS) collected from WSP over grazing paddocks. In particular, P fractions (e.g. labile P as H₂O-P and NaHCO₃-P, and stable P as NaOH-P and HCl-P) were analysed in pond sludge applied soil collected from grazed paddocks. It was found that the application of PS significantly changed the composition of phosphorus in the soil compared with a control paddock that was not treated with PS. The inorganic P in the paddocks treated with pond sludge was 605 mg/kg, which was significantly higher than 67 mg/kg observed in the control paddock. Similarly, the soil treated with pond sludge exhibited increased P fractions of 245%, 36%, 47% and 3000% in terms of H₂O-P, NaHCO₃-P, NaOH-P and HCl-P, respectively, compared with the control paddock. The results of labile and stable P fractions in the soil samples show that PS could be a viable alternative to other forms of commercial fertilizers and a sustainable source of P for the dairy grazing paddocks.

In this study, a vortex-assisted switchable solvent microextraction (VA-SSME) method was developed for the determination of iron by slotted quartz tube flame atomic absorption spectrometry (SQT-FAAS). A ligand synthesized from the reaction of ortho-phenylenediamine and 5-bromosalicylaldehyde was used to form a coordinate complex of iron. All experimental variables such as switchable solvent amount, sodium hydroxide concentration, sodium hydroxide amount, and diluent amount were optimized to increase extraction efficiency for the iron complex. Optimum conditions were applied to aqueous standard solutions in the range of 20–750 ng/mL, and the percent relative standard deviation (%RSD) was less than 2.0%. The limit of detection (LOD) and limit of quantification (LOQ) were determined as 4.8 and 16.2 ng/mL, respectively. The optimized method recorded approximately 53 times enhancement according to the conventional FAAS system. The proposed method was applied to mineral spring water samples, and satisfactory percent recovery results (100–105%) were obtained for iron, indicating good applicability in addition to high accuracy.

Conventional chemical soil amendments and novel material biochars have been widely reported for the immobilisation of cadmium (Cd) and lead (Pb) in polluted soil. However, information regarding their comparative effectiveness is poor. In the present study, rice husk biochar (RHB) was compared with two chemical soil amendments including hydroxyapatite (HAP) and hydrated lime (HDL) for their effectiveness to enhance plant growth and the reduction of Cd uptake and translocation by Triticum aestivum L. grown in heavy-metal-polluted soil. Compared with control and two chemical soil amendments, RHB rapidly improved wheat growth. The HAP, HDL, and RHB treated plants retained Cd and Pb in roots and restricted their translocation. The RHB treatment had the best effect on growth, yield promotion and the reduction of Cd and Pb in wheat grain. Furthermore, the soils treated with RHB and HAP showed lower DTPA-extracted Cd concentrations, and the maximum reduction was observed in HAP-amended soil. However, the DTPA-extracted Pb concentration was not significantly decreased after the application of two chemical soil amendments for 40 days; the maximum reduction was found in soil treated with RHB for 80 days. In all treatments, Cd in post-harvest soil was mainly present in exchangeable, carbonate bound, and Fe-Mn oxide Cd, while the dominant chemical form of Pb was Fe-Mn oxide Pb. Three soil amendments application decreased exchangeable and organic bound- Cd and Pb levels. HAP and RHB displayed significantly immobilisation for soil Cd and reduced translocation of heavy metal as well as its availability in soil, but the HAP had significant inhibition on growth of wheat in contaminated soil. Therefore, RHB shows a promising potential for the reduction of Cd and Pb bioaccumulation in grains from wheat grown on heavy-metal-polluted soils.

Río Tercero Reservoir (RTR) is the largest artificial reservoir in the province of Córdoba (Argentina). Water, sediment, plankton, shrimp (Palaemonetes argentinus), and fish (Odontesthes bonariensis) were collected during the wet season (WS) and dry season (DS) from this reservoir. Concentrations of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, P, Pb, Se, U, and Zn were determined to investigate their respective bioaccumulation pattern and trophic transfer in the food chain. Results showed that their concentrations in water were rather low except Pb, which exceed the limits considered as hazardous for aquatic life. The enrichment factor (EF) in sediments showed that most of the element were derived from anthropogenic sources. Furthermore, the bioaccumulation factor (BAF) determined that the elements undergo bioaccumulation, especially in organisms such as plankton. The invertebrates were characterized by the highest BAF for Cu, P, and Zn in both seasons; Ag, As, and Hg during WS; and Se during DS. Fish muscle registered the highest BAF for Hg (DS) and Se (WS). A significant decrease in Al, As, Cd, Cr, Cu (DS) Fe, Mn, Ni, Pb, Se, U, and Zn (DS) concentrations through the trophic chain was observed, indicating biodilution. Some notable exceptions were found as Cu (WS), Hg (DS), and P (both season) that showed biomagnification. Further studies are needed to establish differential behavior with different species and pollutant, particularly when the potential transfer is to edible organisms.

Bisphenol A (BPA) is considered as xenoestrogen, a crucial component utilized for the manufacturing of plastic products. It has a potential to disrupt the endocrine system and induces endocrine-related metabolic disorders. We aimed to investigate the exposure of BPA in Pakistani population and its association with sociodemographic features, dietary habits, and risk factors of diabetes mellitus (DM). This cross-sectional study was conducted on 400 participants among which 61.75% participants were diabetic and 38.25% were non-diabetic. We developed a structured questionnaire, gathered sociodemographic data, and collected their urine and blood samples for the estimation of BPA and various biomarkers as risk factors of DM, respectively. Pearson correlation coefficient was determined for urinary BPA levels and DM risk factors. Urinary BPA values were adjusted for confounders. Sociodemographic data shown that urinary BPA level was significantly higher (p < 0.05) in obese people (BMI > 27) living in semi-urban and industrial areas. BPA was detectable in 75% of study participants. Urinary BPA level was found to be higher in diabetic participants compared with that of non-diabetics. A significant correlation is observed between BPA exposure and DM risk factors. We found that urinary BPA level was correlated with elevated levels of HbA1c (r = 0.6028), HOMA-IR (r = 0.5356), CRP (r = 0.6946), BUN (r = 0.6077), AST (r = 0.5151), FFA (r = 0.5759), TGs (r = 0.5608), and MDA (r = 0.6908). Hence, our study adds to the growing body of evidence supporting the role of BPA exposure as a risk factor for DM and may be associated with higher glycemic index, increased pro-inflammatory and oxidative stress biomarkers, dyslipidemia, and impaired functioning of the liver and kidney. Heating food in plastic containers and consumption of packed food items are the main sources of BPA exposure which are positively associated with DM.

The escalating generation of biosolids and increasing regulations regarding their safe handling and disposal have created a great environmental challenge. Recently, biosolids have been incorporated into the hydrolysis step of a two-step thermal lipid conversion process to act as water replacement in the production of renewable chemicals and fuels. Here, the hexane extract recovered from hydrolysis of biosolids, lipids from brown grease hydrolyzed using either water (control) or biosolids as a water replacement, was pyrolyzed at 410–450 °C for 2 h. The product distribution and composition were not significantly different when biosolids were used to hydrolyze brown grease instead of water. The liquid product consisted mainly of alkanes, alkenes, aromatics, and cyclic compounds similar to those in petroleum-derived liquid fuels. However, the use of biosolids as a water substitute resulted in a significant increase in sulphur content of the pyrolysate, which will necessitate processes to reduce the sulphur content before or after pyrolysis. Nevertheless, the pathways proposed in this paper are considered as potentially economically viable approaches to not only resolve the issues associated with disposal of biosolids but also to produce renewable hydrocarbons for fuel and chemical applications. Graphical abstract

Low-cost bioadsorbent such as shrimp shell chitin was used for the removal of polyphenols and COD from olive mill wastewater (OMW). In order to achieve a high polyphenols and chemical oxygen demand (COD) removal efficiency and to reduce the number of experiments, two levels of fractional 2⁴ factorial design experiments were carried out. The influence of different experimental parameters such as solution pH, adsorbent concentration, contact time, stirring speed, and their interactions during polyphenols and COD removal were investigated. Optimized values of pH, adsorbent concentration, contact time, and stirring speed were found equal to 12, 10 g/L, 24 h, and 420 rpm/min, respectively. The maximum polyphenol uptake under these experimental conditions reached 69.47%. Whereas the maximum removal of COD achieve 43% in 10 g/L, 12, 24 h, and 80 rpm/min for adsorbent concentration, pH, contact time, and stirring speed as optimal conditions, respectively. The experimental equilibrium data were tested using the Freundlich and Langmuir isotherm models. It was found that adsorption of polyphenols on shrimp shell chitin is well fitted both models. Kinetics of the adsorption process was studied by investigating the pseudo-first-order, pseudo-second-order kinetics, and intraparticle diffusion mechanism and showed that the pseudo-second-order kinetic model provided a better correlation for the experimental data studied in comparison to the pseudo-first-order model and intraparticle diffusion. These results revealed that shrimp shell chitin can be used as an effective and low-cost adsorbent to remove polyphenols and COD from OMW.

A novel sunlight-activated double-shell Cu@Cu₂O/SiO₂ (m-pCu@Cu₂O/SiO₂) photocatalyst is presented via a combined precipitation and sol-gel methods with a mesoporous silica outer shell. After applying several characterization techniques on the m-pCu@Cu₂O/SiO₂, it was tested in the photodegradation of ciprofloxacin (CIP). The experimental results demonstrated a higher photocatalytic activity of the double-shell m-pCu@Cu₂O/SiO₂ nanophotocatalyst than the core-shell pCu@Cu₂O nanophotocatalyst under the sunlight irradiation. When the content of pCu@Cu₂O was 30 wt.%, it showed the highest activity. The Cu nanoparticles exhibited the surface plasmonic resonance (SPR) effect which increased the light absorption in the visible region of light. It also caused the rapid separation of the photoexcited e⁻/h⁺ pairs. Furthermore, the mesoporous structure of outer shell silica favors the transfer of reactants, resulting in the improved photoactivity performance for the supported pCu@Cu₂O catalyst. Central composite design (CCD) based on RSM (response surface methodology) approach was used to optimize four of the most important experimental variables. The photodegraded intermediates were identified by HPLC-Mass.