Optimization Of Removal Process Research Articles

Trimethoprim Removal from Aqueous Solutions via Volcanic Ash-Soil Adsorption: Process Modeling and Optimization

Antibiotic contamination of water sources is a significant environmental and public health concern. This contamination is classified among the most dangerous types of pollution currently because of their harmful effects. Therefore, it is essential to identify effective and environmentally friendly ways to deal with those dangerous compounds. Within this context, this work looked into whether soils made from volcanic ash could be used as cost-effective adsorbents to remove the antibiotic trimethoprim (TRM) from aqueous solutions. To examine the impacts of the main operating parameters on TRM removal, which are the initial antibiotic concentration (C), contact time (t), stirring speed (S), and solid-to-liquid ratio (R), a Central Composite Design (CCD) based on the Response Surface Methodology (RSM) was employed. Full quadratic polynomial models were used to correlate the experimental data, allowing for the estimation of each factor’s influence. With a predicted removal efficiency of 77.59%, the removal process optimization yielded the following set of optimal conditions: C = 4.5 mg/L, t = 45.5 min, S = 747 rpm, and R = 0.04 g/mL. Experiments conducted under predicted ideal conditions supported both the result and the previously developed model’s capacity for prediction. Additionally, the adsorption mechanism was also proposed based on the characterization of the adsorbent before and after the treatment. The study’s findings provide the possibility of using soils formed from volcanic ash as a cost-effective adsorbent material for the removal of TRM and likely other similar pollutants from contaminated waters.

Application of Metal-Organic Frameworks for Efficient Removal of Doxorubicin Hydrochloride: Removal Process Optimization and Biological Activity.

This study looked at the doxorubicin hydrochloride (DOX) anticancer drug's adsorption characteristics on a silver-based metal-organic framework (Ag-MOF). X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) were used for the characterization of Ag-MOF. The pore volume and surface area of Ag-MOF were determined through Brunauer-Emmett-Teller (BET) testing at 77 K to be 0.509 cm3/g and 676.059 m2/g, respectively. Adsorption at pH 6 was established to be the best for DOX compared to alkaline solution. Ag-MOF has a good capacity for eliminating DOX (1.85 mmol/g), according to adsorption experiments. From the adsorption results, we can find that Langmuir is the most fitted adsorption isotherm model and the pseudo-second order model best fitted the adsorption kinetics. The energy of activation for adsorption, which was determined to be 15.23 kJ/mol, also supported a chemisorption process. The mechanism of adsorption was evaluated, and details of all possible interactions between DOX and Ag-MOF were illustrated. On the other hand, while examining the impact of temperature, we identified the thermodynamic constraints as ΔG°, ΔH°, and ΔS° and confirmed that the reaction was an endothermic one and spontaneous. Even after numerous reuse cycles, the efficiency remained constant. The synthetic adsorbent was remarkably recyclable at a rate of more than 91.6%. By using the MTT assay, the cytotoxicity of the tested Ag-MOF and DOX@Ag-MOF against human breast cancer cells (MCF-7) was evaluated in vitro. The in vitro antimicrobial activity of Ag-MOF and DOX@Ag-MOF was also tested.

Unravelling the unique roles of NCQDs over CeFeO3 perovskite as highly efficient photoluminescent solar induced peroxymonosulfate/photocatalyst system: Optimization of removal process, mechanism and degradation pathway

In this work, novel ferrite type CeFeO3 perovskite was elaborately designed with nitrogen-doped carbon quantum dots (NCQDs) for effective degradation of ciprofloxacin (CPX) under peroxymonosulfate (PMS) activated photocatalytic system. The critic roles of NCQDs addition in the PMS-activated system were examined through characterization and photocatalytic tests. The as-fabricated CeFeO3 @NCQDs heterojunction showed superior catalytic performance (92.5 %) which was 2.8 times higher than that of bare CeFeO3 (32.0 %). It was found through XPS analysis that new oxygen-rich bonds were formed in the CeFeO3 @NCQDs sample, providing new reaction sites. PL technique showed that the carrier separation efficiency of the composite was significantly superior to that of the sole CeFeO3 due to excellent electron transfer property of NCQDs. Furthermore, the change in the band energy potentials improved the oxidation ability, resulting in increased degradation rate. The heterojunction catalyst also showed high removal efficiency in real water matrices. Meanwhile, radical trapping tests showed that the superoxide radicals play dominant roles in the photodegradation system. The as-synthesized catalyst also exhibited satisfactory performance in dye decomposition reactions. In addition, Box–Behnken design was applied to find out the optimum conditions which were determined as catalyst dosage of 0.80 g/L, PMS concentration of 4.90 mM and initial CPX concentration of 7.00 mg/L. The CeFeO3 @NCQDs/Vis/PMS system could be considered as a promising candidate in the aspect of practical wastewater treatment applications.

Removal of Malachite Green using carbonized material derived from disposable facemasks: optimization of removal process through Box–Behnken design

ABSTRACT Water resources are being heavily contaminated due to the huge load of toxic pollutants released by industrial activities. Among various physical and chemical methods, adsorption is considered as a promising method for rapidly removing contaminants from wastewater. In the present study, a novel carbon-based adsorbent was prepared through controlled pyrolysis of disposable facemasks. The properties of carbonized compound (CC) were characterized by FTIR, XRD, SEM and EDX. The pollutant removal efficiency of CC was initially investigated with synthetic dyes Malachite Green (MG) and Congo Red (CR). The peaks observed in FTIR spectra corresponding to C=O and C=C and C–N functional groups on adsorbed CC surface confirm the interaction between dye and CC. The XRD spectra of CC showed strong peaks at 2θ = 26.629, 27.488, 27.810 and 29.404 which correspond to the disordered graphitic plane. The SEM images of CC showed good porosity nature. A quadratic model was developed through response surface methodology by conducting a series of Box–Behnken design experiments. Adequacy of this model variables was ensured by ANOVA tests at P-value <0.05. The lower P-value (<0.0001) and higher F-value (44.54) of the quadratic model showed it was a significant model for dye removal. Finally, the optimal condition to obtain maximum MG removal (rate >99%) was identified by desirability function as CC 1000 and MG 212 mg/L and adsorption time 180 min. Adsorption kinetic study indicates that a pseudo second-order kinetic model showed the best fit with R 2 = 0.999.

Response surface methodology for strontium removal process optimization from contaminated water using zeolite nanocomposites.

The effective removal of strontium from polluted water is an emerging issue worldwide, especially in Japan, after the destruction of Fukushima's Daiichi Nuclear Power Plant. In the strontium removal process, statistical optimization of associated factors is needed to reduce the quantity of chemicals and the number of experimental trials. In this study, response surface methodology based on the central composite design was employed for assessing the influence of different factors and their interaction effects on the efficiency of strontium removal. We have considered nanoscale zero-valent iron-zeolite (nZVI-Z) and nano-Fe/Cu zeolite (nFe/Cu-Z) as adsorbents for the effective removal of strontium. The results suggested that the studied three factors such as pH, contact time, and concentration are positively related to the adsorption of strontium. That is, the maximum strontium removal occurred at pH, initial concentration, and contact time of 12, 200 mg L-1, and 30 min, respectively. The experimental maximum strontium adsorption capacity of nZVI-Z and nFe/Cu-Z adsorbents is 32.5 mg/g and 34 mg/g, respectively. The present study also showed that the most statistically significant potential contributor was initial concentration, followed by contact time in the removal process. The study indicated that the interaction effect between contact time and initial concentration was statistically important, suggesting the need for a multi-mechanism technique in the removal phase of strontium. Tόth, Langmuir, Dubinin-Astakhov (D-A), Freundlich, and Hill isotherm models were also fitted with the experimental strontium adsorption data, in which the Tόth model fitted best compared to the other models based on the RMSD and R2.

Solvent free microwave synthesis of nano polyaniline-zirconium silicate nanocomposite for removal of nitro derivatives

Nitroaromatic compounds are classified as toxic-carcinogenic pollutants and explosives. The removal of these compounds represents a great challenge. Therefore, the adsorption behaviors of 4-nitrobenzoic acid and 4-nitroaniline onto a fabricated nanocomposite were researched via a green functionalization of zirconium silicate with nano-polyaniline (ZrSiO4–NPANI and 7.22–22.09 nm). Optimization of removal process was examined by different experimental conditions. The adsorption mechanism of nitrocompounds onto ZrSiO4–NPANI was fitted with the pseudo-second-order and both Langmuir and Freundlich models. Excellent recovery of nitrocompounds from tap water (95.4%), industrial wastewater (97.67%) and sea water (95.77%) were established using 25 mg L−1 and 100 ± 1 mg.

Modification of Zeolite by Magnetic Nanoparticles for Organic Dye Removal

Zeolites HY and 13X were modified by magnetic nanoparticles and were denoted as MHY and M13X, respectively. MHY and M13X were characterized by vibrating-sample magnetometry, X-ray diffraction analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, zeta potential, and Brunauer–Emmett–Teller surface area analysis. MHY and M13X were used as adsorbents for the removal of methylene blue (MB) from aqueous solution. Response surface methodology combined with central composite design was used for statistical modelling aimed at the removal process optimization. The effects of the independent variables on the removal process were evaluated, focusing primarily on the solution pH (which was varied in the 3–9 range), temperature (25–55 $$\, {^{\circ }}\hbox {C}$$ ), the adsorbent dose (300–1200 mg/L), and the initial dye concentration (10–40 mg/L). The solution pH and the absorbent dose had the greatest effects on the MB removal rate. The maximum MB removal of 99.85% was achieved using MHY at the optimum conditions ( $$\hbox {pH} = 9,\hbox { temperature} = 53.91\,{^{\circ }}\hbox {C}$$ , initial MB dye concentration $$= 10.23\hbox { mg/L}$$ , and adsorbent $$\hbox {dose} = 1186\hbox { mg/L}$$ ), while 95.9% was achieved using M13X at the optimum conditions ( $$\hbox {pH} = 8.93,~\hbox { temperature} = 53.39\,{^{\circ }}\hbox {C}$$ , initial MB concentration $$=10.05\hbox { mg/L}$$ , and adsorbent $$\hbox {dose} = 1198\hbox { mg/L}$$ ). The equilibrium data of MB adsorption onto M13X and MHY were studied using the linear and nonlinear form of the Freundlich and Langmuir models, with Langmuir providing a better fit. The obtained kinetic statistics indicated that the adsorption kinetics are more accurately represented by a pseudo-second-order model for both adsorbents. Finally, the calculated thermodynamic parameters indicated that the adsorption is spontaneous and endothermic.

Application of Chemometrics for the Optimization of Phosphorus Removal Process by Electrocoagulation

O tratamento de aguas residuais e uma questao que tem sido estudada nos ultimos anos devido ao grande potencial degenerativo do meio ambiente. A disponibilidade de nutrientes, em especial o fosforo, causa a eutrofizacao de rios e lagos. A eletrocoagulacao e uma tecnica de simples aplicacao para a remocao de poluentes. O planejamento experimental multivariado foi utilizado para otimizacao da eficiencia do processo de remocao de fosforo por eletrocoagulacao utilizando um meio sintetico simples. Com base em um planejamento fatorial fracionario e dados da literatura, o potencial aplicado, o tempo de eletrolise e a condutividade inicial do eletrolito foram identificados como variaveis significativas. O planejamento Box-Behnken e a Metodologia de Superficie de Resposta foram entao utilizados para a otimizacao. A amplitude do dominio experimental neste estudo foi limitada pelo equipamento utilizado (maximo de 25 V). Mesmo assim, uma remocao maxima de fosforo de 97,1% foi estimada em potencial de 25 V aplicado por 12,5 min usando uma condutividade inicial de 1,1 mS cm -2 . A validacao do modelo foi realizada e apresentou uma reducao de 92% para a remocao de fosforo, obtendo uma resposta apenas 5,1% abaixo do esperado, o que comprova a confiabilidade do modelo multivariado.

Dummy Poly Gate Removal Process Optimization with Pulsing Plasma Application

High-K metal gate (HKMG) approach has been introduced to enhance the device performance via lowering device current leakage. Dummy poly gate removal (DPGR) process is introduced in HKMG process to form the metal gate with different work functions for n/p-MOS. However, the introduction of this technology does bring many new challenges to process, especially for etch process. Before the second dummy gate is removed, the first dummy gate has been replaced with metal materials. This definitely requires soft etch process to avoid the damage of gate channel and the first metal gate while meet all the physical targets. In this paper, we leveraged synchronous pulsing/source pulsing scheme to fulfill the precise geometry definition and achieve the requirement of device performance.

Dummy Poly Gate Removal Process Optimization with Pulsing Plasma Application

The technology of High-K/metal gate has led to the continuity of device scaling and enabled the extension of Moore’s Law towards 28 nm node and beyond. The gate last approach has been widely adopted since it can better control n/p-MOS transistor threshold voltage (Vt), hence yielding better electrical performance [1]. However, it poses the formidable challenges to every process of metal gate formation, especially for the 2nd DPGR (dummy gate removal) process. In order to get the robust device performance, the 2nd-DPGR [2] process needs to fully consider all kinds of tangled aspects such as trench profile, n/p-MOS boundary interface, ILD (Interlayer dielectric) loss, Al damage, trench poly residue, trench corner residue, PID (plasmas induce damage), HK capping layer loss and surface residue. In this work, we will first introduce the various dilemma of the 2nd DPGR with conventional CW (continuous wave) plasma approach, and demonstrate the hybrid pulsing scheme could completely solve the aforementioned issues. Synchronous and source-only pulsing plasma have been introduced in the different etch steps of the 2nd DPGR. Synchronous pulsing scheme is proven to achieve vertical trench profile, clean n/p-MOS boundary, precisely-controlled oxide loss/Al damage. While, source-only pulsing PET (post etch treatment) is effective in terms of HK capping layer loss control without sacrificing the ability of interface treatment. 1.Trench Bottom Profile and n/p-MOS Boundary Perfect trench profile could alleviate the gap-fill difficulty and deliver the more reliable device performance. In the 2nd DPGR process, too much profile pull-back at trench bottom is not acceptable. This necessitates the demand for extremely anisotropic dry etching. Besides, n/p-MOS boundary connects the pull -up area and the pull-down area, highly related to ring oscillation performance. As is well known, the produced etching polymer/by-product inevitably adheres to n/p-MOS boundary during DPGR for the high selectivity of poly-si over oxide is required to avoid the excessive oxide loss. However, such polymer/by-product needs to be fully removed before metal gap-fill. Seemingly, even if CW plasma could leverage the extra either in-situ step or ex-situ step to thin down such polymer/by product layer. However, we found there is a trade-off relationship between trench bottom profile and n/p-MOS boundary. On another side, pulsing plasma paves the way to seek the common process window for the above two targets. In synchronous pulsing plasma, the polymer/by-products could be pumped out easily during the plasma-off time and more positive charges could be neutralized at trench bottom. With the proper frequency and duty cycle, we achieved the vertical trench profile with clean n/p-MOS boundary as shown in Fig 1a and b. 2.ILD Loss, Al Damage and Poly Residue In the 2nd DPGR process, the sufficient hard-mask OE (over-etch) process must be kept to avoid poly-Si residue at trench bottom. However, the excessive OE will induce serious Al damage and more ILD loss. The former could result in Al corrosion; the latter could tend to suffer n/p-MOS bridge risk because of metal residue after CMP (chemical mechanical polishing). Finally, we leveraged the synchronous pulsing scheme to tackle both issues from the point of view of less bombardment. 3.Bottom Corner Residue and PID HBr/O2, the typical silicon etch process, tends to suffer trench bottom corner residue. This could reduce the effective channel length, introduce process variation and worsen Vt mismatch. To solve this issue, we resorted to NF3/H2 gas combination to fully remove trench corner residue. However, the device test randomly shows PID issue. This might be the fact that H atom could easily damage HK oxide and/or its capping layer at higher electron temperature under CW plasma mode. Again, synchronous pulsing plasma can balance both corner residue and PID issue as it can reduce the averaged electron temperature to a very low level and the electron shading effect by neutralizing the electron accumulated at trench bottom. 4.Capping Layer Loss and Its Interface HK capping layer is used to protect HK oxide from direct plasma bombardment. The thickness and surface roughness of capping layer are very critical to the adjustment of gate work function, leakage and reliability control. In this work, we came up with the source-only pulsing PET and have proven that it is capable of rigorously controlling capping layer loss without sacrificing the ability of interface treatment. Acknowledgement This work is partially sponsored by Shanghai Rising-Star Program (B type). [1] P. Lim et al, USP, 7871915 B2 “Method for forming metal gates in a gate last process”, 2011 [2] Jack Huang, et al, SPIE, “Synchronous Pulsing Plasma Utilization in Dummy Poly Gate Removal Process”, 2015 Figure 1

Decontamination of ofloxacin: optimization of removal process onto sawdust using response surface methodology

Ofloxacin is one of the most used fluoroquinolones, a potent broad spectrum antibiotic class; it is also included in pharmaceutically active compounds that are considered as environmental pollutants. To clean the water systems sorption has been found as an effective way to remove these pollutants. Present study demonstrates the effect of different sawdust treatments on removal of ofloxacin from aqueous solutions. The sorption of ofloxacin by treated sawdust has been optimized by response surface methodology using central composite design. Set of 18 experiments was used and factors as pH, amount of sorbent, contact time, and concentration of sorbate were considered the critical factors to be studied for removal. HCl-treated sawdust was found to have maximum removal efficiency (96%) with the sorption capacity of 47 μmol g−1 as compared to other treated sorbents. Amount of sorbent have significantly positive impact on the removal for all three treated sorbents whereas concentration of sorbate has non-significant positive effect for HCl-treated sawdust. Further, sorption isotherms, kinetics, and thermodynamics studies onto HCl-treated sawdust showed that reaction is exothermic and spontaneous in nature and psuedo-second-order is predominant route. Complex sorption mechanism with simultaneous intraparticle diffusion as well as surface adsorption phenomena is responsible for sorption of ofloxacin onto sawdust.

The Study of How to Reduce ILD Loss in High-k and Metal Gate Last Process

High-k last and metal gate last process becomes the main stream in 20nm and beyond technology. In high-k last process, the thermal dummy gate oxide (DGO) must be removed before the growth of interfacial layer (IL). In conventional process, to avoid the plasma damage to the device, wet etch is the most popular process to remove DGO. Because the etch rate of ILD(inter layer dielectric) oxide and CESL(CT etch stop layer) layers is much higher than thermal oxide, during the removal of DGO, serious ILD and CESL loss is observed, which will induce many of following process issues, such as high-k/metal residue, gate height variation, work function shift, etc. In this paper, multi-methods are studied to reduce the loss of ILD and CESL layer. The study mainly includes improvements on film quality and optimization of removal process. Finally, the selectivity of ILD oxide and CESL to thermal dummy gate oxide can reach ~1:1.

Material removal process optimization for milling of flexible workpiece considering machining stability

The material removal process of a flexible workpiece has a great effect on the stability limits and chatter-free machining time, as the sequence of material removal can be altered to obtain a better workpiece dynamic behaviour. Therefore, the uncut material can be better designed to get chatter-free machining conditions and a shorter machining time. With this as the objective, a material removal process optimization method is presented to design the uncut material distribution. Different from existing methods, the presented approach begins from the last machining step, the maximum stable cutting depth is calculated, and the removed material is virtually added to the design model. Therefore, beginning from the design part, the material is virtually added to the part and the stock model of the part is finally obtained. Based on this approach, the optimized uncut material can provide support for the part in the semi-finish or finish machining processes, and the machining process is stable. Optimization results show that while machining plate-like structures, step removal methods can be used and the arc or triangle shape machining allowance can be used to get better machining results. Cutting experiments were carried out to show the effectiveness of the presented approaches.

Nitrogen removal process optimization in New York City WPCPS: a case study of Wards Island WPCP

The New York City Department of Environmental Protection has been engaged in a continuous process to develop a nitrogen removal program to reduce the nitrogen mass discharge from its water pollution control plants, (WPCPs), from 49,158 kg/d to 20,105 kg/d by the year 2017 as recommended by the Long Island Sound Study. As part of the process, a comprehensive research effort was undertaken involving bench, pilot and full scale studies to identify the most effective way to upgrade and optimize the existing WPCPs. Aeration tank 13 (AT-13) at the Wards Island WPCP was particularly attractive as a full-scale research facility because its aeration tank with its dedicated final settling tanks and RAS pumps could be isolated from the remaining treatment facilities. The nitrogen removal performance of AT-13, which, at the time, was operated as a "basic step feed BNR Facility", was evaluated and concurrently nitrification kinetic parameters were measured using in-situ bench scale experiments. Additional bench scale experiments provided denitrification rates using different sources of carbon and measurement of the maximum specific growth rate of nitrifying bacteria. The combined findings were then used to upgrade AT-13 to a "full" BNR facility with carbon and alkalinity addition. This paper will focus on the combined bench and full scale results that were the basis for the consequent upgrade.

Removal of nickel(II) ions from aqueous solution by biosorption in a fixed bed column: Experimental and theoretical breakthrough curves

The nickel(II) ions biosorption process by marine algae Sargassum filipendula in a fixed bed column was investigated for the following experimental conditions: temperature = 30 °C and pH 3.0. The experimental breakthrough curves were obtained for the following chosen flow rates 0.002, 0.004, 0.006, and 0.008 L/min. A mathematical model was developed to describe the nickel ion sorption in a fixed bed column. The model of three partial differential equations (PDE) has considered the hydrodynamics throughout the fixed bed column as well as the sorption process in the liquid and solid phases. The internal and external mass transfer limitations were considered, as well. The nickel ion sorption kinetics has been studied utilizing the Langmuir isotherm. The PDE of the system were discretized in the form of ordinary differential equations (ODE) and were solved for the given initial and boundary conditions using the finite volume method. A new correlation for external mass transfer coefficient was developed. Some of the model parameters were experimentally determined ( ɛ, d p) where the others such as ( K F, K S) were evaluated on the base of experimental data parameters. The identification procedure was based on the least square statistical method. The robustness and flexibility of the developed model was checked out using four sets of experimental data and the predictive power of the model was evaluated to be good enough for the all studied cases. The developed model can be useful tool for nickel ion removal process optimization and design of fixed bed columns using biomass of S. filipendula as a sorbent.