Full Factorial Design Approach to Hg(II) Adsorption onto Hydrogels

Optimisation of the machining time required by insole orthotic shoes for patients with clubfoot using the Taguchi and response surface methodology approach

In this study, the application of the computer-aided reverse engineering system (CARE) to the novel design and manufacture of a comfortable insole for a clubfoot patient is presented. The Taguchi method (TM) and response surface methodology (RMS) were used to predict the machining time of the orthotic boot insole during both computer-aided manufacturing (CAM) simulation and computer numerical control (CNC) machining. Taguchi's experimental design, presented as a matrix orthogonal array L₂₇3⁶, was acquired for controlling parameters, namely tool path strategy (A), spindle speed (B), step-down (C), step-over of the cutter (D), cutter diameter (E), and dimensional tolerance (F) of the insole size. In this method, the model generated by the RMS method evaluates the six parameters influencing the machining time. The objective of this study is to develop a regression model that demonstrates the relationship between the cutting parameters and insole machining time. The optimal parameters are A₁B₁C₃D₂E₁F₂, where A₁ denotes raster finishing, B₁ denotes a spindle speed of 10,000 rpm, C₃ denotes a step-down of 850 mm, D₂ denotes a step-over of 0.25 mm, E₁ denotes a cutter diameter of 20-35 mm, and F₂ deontes a tolerance of 0.75 mm. The experimental and calculated machining time (t_m) results were 236 and 125.4 min, respectively. However, the real machining results were 334 and 152.25 min with error values of 46.86% and 54.42%, respectively. Meanwhile, with the t_m RMS method, the simulated and calculated machining time results were 189.22 and 236.35 min, whereas the real t_m values were 236.52 and 334.86 min with error values of 19.94% and 29.37%, respectively. This research obtains improvements of 19.82% (simulation time) and 29.19% (real-time).

Heat and ZnCl2 chemical carbonization of date stone as an adsorbent: optimization of material fabrication parameters and adsorption studies

In the present study, the optimization of factors for the fabrication of highly adsorptive activated carbon from agricultural waste (date stone) was investigated by using ZnCl₂ as a chemical agent during the heat treatment. ZnCl₂ acts as a dehydration agent during the heat treatment, allowing a better porosity. In addition, it boosts the fragmentation of the lignocellulosic structure and the condensation of carbon rings. The findings of this investigation showed that the synthesis conditions for better ZnCl₂ chemical/heat carbonization to fabricate an adsorbent from date stone are 700 °C, 120 min, and 2.0 g/g. The characterization analysis showed that the as-prepared activated carbon exhibits a surface area of 1036 m²/g, an iodine number of 928.5 mg/g, and phenol number of 2.1 mmol/g, which are comparable to commercial activated carbons. Batch sorption tests to remove methylene blue (MB) from water showed a maximum adsorption capacity of 384.6 mg/g using the prepared activated carbon. Equilibrium data was best fitted by the Langmuir isotherm model. It was found also that the kinetic adsorption data obeyed the pseudo-first order, and both external diffusion and intra-particle diffusion control the adsorption. Based on the obtained results, the optimization of synthesis conditions may help the transfer of technology in terms of agriculture-based material valorization towards the environmental remediation.

A new approach to evaluate toxic metal transport in a catchment

Competitive sorption and desorption of Cd²⁺, Pb²⁺, and Hg²⁺ onto riverbank and sediment samples of an area impacted by pyritic residue in a Southern Brazilian catchment were evaluated. Although these ions are considered poorly mobile, a new approach has been proposed to assess their behavior and associated risk. In this sense, factorial design and three-dimensional surface methodology are proposed to describe the competitive sorption behavior of the metal ion in the environmental matrix, as well as an innovative mobilization factor (MF) to describe the desorption rate from the integration of the normalized difference of sorption-desorption fluorescence peaks. Sorption was carried out with a central composite factorial design (2³) to estimate simultaneous effects of independent variables. Three-dimensional surface analysis indicated increasing Cd²⁺ equilibrium concentration (C_eq) with Hg²⁺ and Pb²⁺ initial concentration (C_i), showing synergistic effect and low Cd²⁺ affinity to the solid phase. Statistical analysis presented [Formula: see text] as a significant variable for cadmium and lead dynamics, although [Formula: see text] was also significant for Hg²⁺ releasing to the liquid phase. After integrating the sorption and desorption fluorescence peaks, the MF for Cd²⁺, Pb²⁺, and Hg²⁺ was around 0.2, 0.5, and 0.1 in riverbank sediment, and 0.3, 0.9, and 0.1 in sediment, respectively. Hence, consistent ion mobilization along the river was observed, with Pb²⁺ mobilizing 9 and 6 times more than Hg²⁺ and Cd²⁺, respectively. The transport of ions such as Pb²⁺ and Hg²⁺, usually considered immobile, has indeed occurred, causing contamination through the watershed and increasing environmental risk. Graphical Abstract A new approach to determine toxic metal mobilization factor in a river catchment.

A comparative study of an up-flow aerobic/anoxic sludge fixed film bioreactor and sequencing batch reactor with intermittent aeration in simultaneous nutrients (N, P) removal from synthetic wastewater

The performance of two bench scale activated sludge reactors with two feeding regimes, continuous fed (an up-flow aerobic/anoxic sludge fixed film (UAASFF) bioreactor) and batch fed (sequencing batch reactor (SBR)) with intermittent aeration, were evaluated for simultaneous nutrients (N, P) removal. Three significant variables (retention/reaction time, chemical oxygen demand (COD): N (nitrogen): P (phosphorus) ratio and aeration time) were selected for modeling, analyzing, and optimizing the process. At high retention time (≥6 h), two bioreactors showed comparable removal efficiencies, but at lower hydraulic retention time, the UAASFF bioreactor showed a better performance with higher nutrient removal efficiency than the SBR. The experimental results indicated that the total Kjeldahl nitrogen removal efficiency in the UAASFF increased from 70.84% to 79.2% when compared to SBR. It was also found that the COD removal efficiencies of both processes were over 87%, and total nitrogen and total phosphorus removal efficiencies were 79.2% and 72.98% in UAASFF, and 71.2% and 68.9% in SBR, respectively.

Synthesis of carbon loaded γ-Fe2O3 nanocomposite and their applicability for the selective removal of binary mixture of dyes by ultrasonic adsorption based on response surface methodology

The contemporary problems concerning water purification could be resolved by using nanosorbents. The present studies emphasis on the synthesis of γ-Fe₂O₃-activated carbon nanocomposites (γ-Fe₂O₃-NP-AC) by sol-gel method. The composition and surface morphology of them were studied by FTIR, EDS, SEM and XRD techniques. Moreover they were employed for the selective removal of binary mixture of dyes including reactive red 223 dye (RR) and Malachite Green dye (MG) by ultrasonic assisted adsorption method. Sonication is the act of applying sound energy to agitate particles in the sample. The ultrasonic frequencies (>20kHz) were used to agitate experimental solutions in current studies. The response surface methodology based on 5 factorial central composite design (CCD) was employed to investigate the optimum parameters of adsorption. The optimum operating parameters (OOP) including sonication time, solution pH, amount of adsorbent, concentration of RR and MG were estimated for the selective removal of mixture of dyes. On OOP conditions of RR, the % removal of RR and MG were observed to be 92.12% and 10.05% respectively. While at OOP of MG, the % removal of MG and RR were observed to be 85.32% and 32.13% from the mixture respectively. Moreover the mechanisms of adsorption of RR and MG on the γ-Fe₂O₃-NP-AC were also illustrated. The significance of the RR-γ-Fe₂O₃-NP-AC and MG-γ-Fe₂O₃-NP-AC adsorption models was affirmed by ANOVA test. The Pareto plots for the selective removal of the RR and MG from the binary mixture also confirm the significance of the factors. Isothermal studies were performed and RR adsorption was observed to follow Langmuir isotherm model whereas MG adsorption was observed to follow Freundlich model. Thermodynamic studies were conducted and the outcomes suggested the spontaneous nature of adsorption processes. The kinetic models were employed to study the kinetics of the process. It was observed that the system followed pseudo second order, intra-particle diffusion and Elovich models as represented by the R² values of the respective models. The comparative study from the previously studies revealed that the proposed method is amongst them is the most efficient method to eliminate RR and MG dyes from the aqueous medium. Therefore the current study will be useful in reducing the toxicity of RR and MG contaminated effluent.

Impact of pulsed ultrasound on bacteria reduction of natural waters

There is a limited work on the use of pulsed ultrasound for water disinfection particularly the case of natural water. Hence, pulsed ultrasound disinfection of natural water was thoroughly investigated in this study along with continuous ultrasound as a standard for comparison. Total coliform measurements were applied to evaluate treatment efficiency. Factorial design of 2(3) for the tested experimental factors such as power, treatment time and operational mode was applied. Two levels of power with 40% and 70% amplitudes, treatment time of 5 and 15 min and operational modes of continuous and pulsed with On to Off ratio (R) of 0.1:0.6 s were investigated. Results showed that increasing power and treatment time or both increases total coliform reduction, whereas switching from continuous to pulsed mode in combination with power and treatment time has negative effect on total coliform reduction. A regression model for predicting total coliform reduction under different operating conditions was developed and validated. Energy and cost analyses applying electrical and calorimetric powers were conducted to serve as selection guidelines for the choosing optimum parameters of ultrasound disinfection. The outcome of these analyses indicated that low power level, short treatment time, and high R ratios are the most effective operating parameters.