This paper deals with the comprehensive analysis for the removal of silver nanoparticles (AgNPs) from water environment. A new activated carbon derived from an agricultural waste, water lily mango seed shells, was proposed as a low-cost adsorbent to remove AgNPs. In addition, a new simple kinetic model was mathematically formulated and then tested using primary and secondary experimental AgNP adsorption data on different adsorbents. Moreover, cost analysis for the activated carbon production and removal of AgNPs was also estimated. Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and inductively coupled plasma mass spectroscopy (ICPMS) analyses were employed for the characterization. The proposed model evaluation was carried out using six statistical indicators, which are the coefficient of determination (R²), root mean squared error (RMSE), percentage of error in maximum estimated value (Eₘₐₓ), percentage of error in minimum estimated value (Eₘᵢₙ), mean absolute percent error (MAPE), and mean absolute deviation (MAD). This study found that the proposed activated carbon performed a rapid removal with a maximum percentage of up to 97%. It was also interesting to note that the proposed model outperformed existing kinetic models having the same number of parameters. Cost analysis carried out in this study exhibited that the activated carbon was highly economical compared with other water treatment technologies reported elsewhere.

Cadmium and mercury are non-biodegradable toxic metals that may cause many detrimental effects to the thyroid gland and blood. Vitamin C has been found to be a significant chain-breaking antioxidant and enzyme co-factor against metal toxicity and thus make them less available for animals. The current study was performed to find the effect of individual metals (cadmium and mercury), their co-administration, and the ameliorative effects of vitamin C on some of the parameters that indicate oxidative stress and thyroid dysfunction. Cadmium chloride (1.5 mg/kg), mercuric chloride (1.2 mg/kg), and vitamin C (150 mg/kg of body weight) were orally administered to eight treatment groups of the rabbits (1. control; 2. Vit C; 3. CdCl₂; 4. HgCl₂; 5. Vit C + CdCl₂; 6. Vit C + HgCl₂; 7. CdCl₂ + HgCl₂, and 8. Vit C + CdCl₂ + HgCl₂). After the biometric measurements of all experimental rabbits, biochemical parameters viz. triidothyronine (T₃), thyroxine (T₄), thyroid-stimulating hormone (TSH), and triglycerides were measured using commercially available kits. The results exhibited significant decline (p < 0.05) in mean hemoglobin, corpuscular hemoglobin, packed cell volume, T₃ (0.4 ± 0.0 ng/ml), and T₄ (26.3 ± 1.6 ng/ml) concentration. While, TSH (0.23 ± 0.01 nmol/l) and triglyceride (4.42 ± 0.18 nmol/l) were significantly (p < 0.05) increased but chemo-treatment with Vit C reduces the effects of Cd, Hg, and their co-administration but not regained the values similar to those of controls. This indicates that Vit C had a shielding effect on the possible metal toxicity. The Cd and Hg also found to accumulate in vital organs when measured by atomic absorption spectrophotometer. The metal concentration trend was observed as follows: kidney > liver > heart > lungs. It was concluded that Cd and Hg are toxic and tended to bioaccumulate in different organs and their toxic action can be subdued by vitamin C in biological systems.

In this study, the cellulose nanocrystals (CNC) obtained by acid hydrolysis of microcrystalline cellulose (MCC) are customized by suspension to obtain a spherical CNC hydrogel. The N-(2-aminoethyl) (3-amino-propyl) methyldimethoxyansile (AEAPMDS) preparation was grafted to spherical CNC hydrogel using a water phase heat treatment. Finally, aerogel samples were obtained by tert-butanol replacement and freeze-drying. The test results confirmed that the aminosilane was grafted on CNC. Electron micrographs and N₂ sorption isotherms showed that the pores of the aerogel were partially blocked due to the introduction of AEAPMDS, and the specific surface area was decreased. Due to the presence of chemisorption, the amount of CO₂ adsorbed at a pressure of 3 bar by the modified aerogel (2.63 mmol/g) was greatly improved compared with the unmodified aerogel (0.26 mmol/g), and the adsorption results were fit well by the Langmuir model. Thus, our experiments provided the opportunity to develop a new CO₂ absorbent material.

In this study, the synthesis of iron oxide stabilized by chitosan was carried out for the application and optimization in the removal process of aqueous Cr(VI) by central composite design (CCD). The calculation of these effects allowed to know, quantitatively, the variables and the interaction between them that could affect the Cr(VI) removal process. It was also verified that the most favorable conditions for chromium removal were the following: pH 5.0, Cr(VI) concentration of 130 mg L⁻¹, adsorbent mass of 5 mg, and Fe(II) content of 45% (w/w) in the CT-Fe beads. The adsorption kinetics performed under these conditions showed that the chitosan/iron hybrid composite is an adsorbent material with high chromium removal capacity (46.12 mg g⁻¹). It was found that all variables were statistically significant. However, it was observed that the variable that most affected Cr(VI) removal was the pH of the solution, followed by the concentration of chromium ions in solution and the interaction between them. Therefore, the studied experimental conditions are efficient in chromium adsorption, besides the operational simplicity coming from statistical design. Theoretical calculations showed that the most stable chitosan was that with Fe(II) in the structure, that is, in the reaction mechanism, there is no competition of Fe(II) with Cr(III, VI) in the available sites of chitosan. Thus, the theoretical calculations show that the proposed Cr(VI) removal is effective.

Steady efforts in using ultrasonic energy to treat oil-contaminated sand started in the early 2000s until today, although pilot studies on the area can be traced to even earlier dates. Owing to the unique characteristics of the acoustic means, the separation of oil from sand has been showing good results in laboratories. This review provides the compilation of researches and insights into the mechanism of separation thus far. Related topics in the areas of oil-contaminated sand characterizations, fundamental ultrasonic cleaning, and cavitation effects are also addressed. Nevertheless, many of the documented works are only at laboratory or pilot-scale level, and the comprehensive interaction between ultrasonic parameters towards cleaning efficiencies may not have been fully unveiled. Gaps and opportunities are also presented at the end of this article.

This study investigated the effects of residual ozone on the performance of microorganisms treating petrochemical wastewater using batch experiments with low and high ozone dosages (5.0 mg/L and 50.0 mg/L, respectively). The results indicated that the low residual ozone concentration significantly increased COD removal by 24.21% in the biological process compared to control group with no ozone residual, while the high residual ozone concentration showed the opposite effect. In the reactor with low residual ozone concentration (0.45 mg/L), the amount of loosely bound (LB)-extracellular polymeric substances (EPS) in the activated sludge decreased by 23.23%, while the amount of tightly bound (TB)-EPS increased by 129.16% compared to the none-ozone residual reactor. In addition, the low residual ozone was found to improve the bioactivity of activated sludge by 139.73% in the first 30 min of the biological process. In the reactor with high residual ozone concentration (0.91 mg/L), both LB- and TB-EPS of the activated sludge increased, while bioactivity decreased. This implies that low residual ozone in a bio-reactor can enhance microbial activity by increasing contact between the pollutants and cells by removing LB-EPS covering the outer layer of the sludge. The microorganisms in the sludge samples could be classified into three groups representing those that are susceptible to ozone, tolerant to low dose of residual ozone, and resistant to high dose of residual ozone. The resistant bacteria Gemmatimonadaceae uncultured became predominant, with a relative abundance of 11.37%, under low residual ozone conditions, while it decreased at high ozone concentrations. The results showed that a certain amount of residual ozone could stimulate the activity of microorganisms by altering the EPS fraction and structure of the microbial community, and thus it is important for the removal of refractory organics from wastewater in the ozone-biological process.

In this study, we investigated the effect of acute administration of gold nanorods (AuNRs) on testicular function, sexual hormones, and oxidative stress parameters in male albino rats. Forty mature male albino rats were divided into two equal groups (n = 20/each). The first group received 1 ml saline solution intraperitoneally (i.p.). The second group received single i.p. injection of 75 μg 50 nm AuNRs/kg/bwt. Five rats from each group were sacrificed on days 1, 3, 7, and 14 post treatment and blood samples were collected for hormonal and biochemical analysis. Testes were collected from each group at each time point for histopathology, morphometric, and transmission electron microscope analyses of testis and epididymis. Results indicated that i.p. injection of AuNRs did not produce any histopathological changes. Morphometric analysis of testicular samples revealed that the height of lining epithelium was significantly (P < 0.05) higher in AuNR group on days 3 and 14 post treatment, and the minor axis of seminiferous tubules was higher (P < 0.05) in AuNR-injected rats than in control group. For the epididymis, the number of spermatozoa was significantly (P < 0.05) higher on days 7 and 14 after AuNR injection when compared with control rats. AuNRs were not detected by TEM at all time points of the experiment. Serum analysis demonstrated that total and free testosterone values significantly (P < 0.05) increased on days 1, 3, 7, and 14 post AuNR injection. LH was higher (P < 0.05) in AuNRs-injected rats on days 3, 7, and 14 post injection, while FSH values were higher (P < 0.05) in AuNR group on days 3 and 14. Malondialdehyde significantly (P < 0.05) decreased on days 3, 7, and 14 in AuNR group, while catalase, glutathione peroxidase, and superoxide dismutase values were significantly (P < 0.05) elevated on days 3, 7, and 14 in AuNRs-injected rats compared with control group. In conclusion, intraperitoneal injection of 50 nm AuNRs is safe on the reproductive function and has an antioxidant action.

Iron-incorporated silica (Fe/SiO₂) with different Fe/Si molar ratio was successfully prepared from rice husk pyrolytic residues (RHR) through alkali pretreatment, co-precipitation, and calcination. Various characterization methods indicated that the Fe/SiO₂ samples possessed mesoporous structure with Fe species incorporated into the framework of silica. The obtained materials were applied in the treatment of hazardous banknote printing wastewater, and under the optimal conditions, colored pollutants, humic acid-like and soluble microbial by-product-like organics were removed significantly. It was found that Fe/SiO₂ acted as both flocculant and catalyst, and the framework iron species catalyzed the oxidative degradation of refractory organics in the presence of H₂O₂. A heterogeneous Fenton-like system was formed in the wastewater treatment process.

Management procedures (MPs) based on data-limited methods (DLMs) recently developed to give management advices for data-limited stocks worldwide are scarce or yet to be implemented on freshwater species. In this study, case studies (CSs) were developed using length-frequency data (LFD) of common carp species harvested from Dianshan Lake to estimate life-history parameters from existing methods. These CSs were later used to examine their influences when tested with various MPs under scenarios when operating models (OMs) were subjected to observation and estimation uncertainties. The results after management strategy evaluation (MSE) was run for various defined OMs showed that three MPs emerged best for providing managing advice. For high yield to be maintained during short-term periods, MinlenLopt1 suggested the smallest length at full retention (sLFR) to be 42.11 cm; while Slotlim and matlenlim2 suggested that to maintain biomass and stable spawning biomass (SBMSY) and also avoid overfishing from occurring in this fishery, sLFR should be 56.1 cm. Values given by these MPs allowed the removal of species that spawned at least once. Also, life-history parameters derived from CS4 presented the best results, being more reliable in presenting better inputs for effective management of the said fishery.

The efficient removal of heavy metals from aqueous environment is imperative and challenging. A novel ternary composite constructed of diaminopyridine polymers, graphene oxide, and ferrite magnetic nanoparticles was designed by a facile in situ polymerization strategy for the removal of Pb(II) from aqueous solution. Detailed characterization of morphological, chemical, and magnetic properties was employed systematically to confirm the formation of the composite material. Batch adsorption experiment studies suggested that the composite was an excellent adsorbent for Pb(II) which was easily collected after use via exposure to an external magnetic field for 30 s. The effects of different parameters such as solution pH, adsorbent dosage, contact time, initial Pb(II) concentration, temperature, and co-existing ions were examined. The maximum adsorption capacity at pH = 5 was estimated to be 387.2 mg g⁻¹ at 298 K by the Langmuir isotherm model, accompanied by favorable adsorption recyclability according to the investigation of regeneration experiments. Thermodynamic studies revealed that the Pb(II) adsorption via our ternary composite was endothermic and spontaneous. The corresponding removal performance for effluent containing Pb(II) from the battery industry was successfully examined. The present results indicated that our designed adsorbent is beneficial to the practical Pb(II) removal in wastewater purification.