Predicting molecular docking of per- and polyfluoroalkyl substances to blood protein using generative artificial intelligence algorithm DiffDock.

This study computationally evaluates the molecular docking affinity of various perfluoroalkyl and polyfluoroalkyl substances (PFAs) towards blood proteins using a generative machine-learning algorithm, DiffDock, specialized in protein-ligand blind-docking learning and prediction. Concerns about the chemical pathways and accumulation of PFAs in the environment and eventually in the human body has been rising due to empirical findings that levels of PFAs in human blood has been rising. DiffDock may offer a fast approach in determining the fate and potential molecular pathways of PFAs in human body.

Impacts of Diet on Reproductive Performance of Captive American Alligators (Alligator mississippiensis).

Historically, there has been little success with the captive breeding of American alligators (Alligator mississippiensis) for both commercial and conservative purposes. This study, conducted at Golden Ranch in Gheens, LA, between 2016 and 2022, utilized a newly formulated commercial feed and practical dietary supplementation (crawfish waste products) to enhance egg production, fertility, and hatch rates. The primary focus of this study was to compare the outcome of this captive breeding program at Golden Ranch with a program conducted at Rockefeller Refuge (RR) between 1979 and 1984. Notable success was achieved in terms of reproductive performance in comparison to the captive breeding program conducted at Rockefeller Refuge. In this study, 16.1 hatchlings were produced per nest on Golden Ranch from captive breeders. Additionally, when wild nests from Golden Ranch were incubated in the same controlled environmental chambers, they produced an average of 16.3 hatchlings per nest. This comparison emphasizes the similarity in egg production between captive-bred A. mississippiensis and their wild counterparts. The findings of this study suggest that a closed farming system for A. mississippiensis can be established by employing captive breeders derived from artificially incubated wild eggs. Furthermore, American alligators raised in controlled environmental chambers during their initial three years of life demonstrated adaptability to captive conditions and tolerated stocking rates associated with farming conditions and served as breeding stock.

A review of PFAS adsorption from aqueous solutions: Current approaches, engineering applications, challenges, and opportunities.

Per- and polyfluoroalkyl substances (PFAS) have drawn great attention due to their wide distribution in water bodies and toxicity to human beings. Adsorption is considered as an efficient treatment technique for meeting the increasingly stringent environmental and health standards for PFAS. This paper systematically reviewed the current approaches of PFAS adsorption using different adsorbents from drinking water as well as synthetic and real wastewater. Adsorbents with large mesopores and high specific surface area adsorb PFAS faster, their adsorption capacities are higher, and the adsorption process are usually more effective under low pH conditions. PFAS adsorption mechanisms mainly include electrostatic attraction, hydrophobic interaction, anion exchange, and ligand exchange. Various adsorbents show promising performances but challenges such as requirements of organic solvents in regeneration, low adsorption selectivity, and complicated adsorbent preparations should be addressed before large scale implementation. Moreover, the aid of decision-making tools including response surface methodology (RSM), techno-economic assessment (TEA), life cycle assessment (LCA), and multi criteria decision analysis (MCDA) were discussed for engineering applications. The use of these tools is highly recommended prior to scale-up to determine if the specific adsorption process is economically feasible and sustainable. This critical review presented insights into the most fundamental aspects of PFAS adsorption that would be helpful to the development of effective adsorbents for the removal of PFAS in future studies and provide opportunities for large-scale engineering applications.

Formulation of a Simulated Wastewater Influent Composition for Use in the Research of Technologies for Managing Wastewaters Generated during Manned Long-Term Space Exploration and Other Similar Situations-Literature-Based Composition Development.

The prospect of humans inhabiting planetary bodies is gaining interest among research and development communities, with the moon being considered as a transitory base camp and Mars the next planet humans will inhabit. NASA's Mission to Mars program is set to have humans inhabiting Mars within on-planet space camps by the Year 2030, which has tremendously increased research and development for space exploration-including research oriented toward human life support in long-term planetary lodging camps. The sustenance of human life on Mars will not be trivial due to the unavailability of an appropriate atmosphere and usable water. This situation requires a self-sustaining human life support system that can provide the basic needs such are breathable air, potable water, food, and energy. The feasibility of sending a payload with resources adequate to support long-term human inhabitation is not reasonable, which means every resource within a Mars space camp is valuable, including human-produced wastes. A biorefinery system that treats wastewater and can also produce valuable products such as oxygen, food, and energy offers a form of circular utilization of valuable resources. To conduct research for such systems requires a wastewater influent that is representative of the wastewater to be generated by the space crew within this isolated, confined environment, which is different from what is generated on Earth due to limited variability in diet, human activity, and lifestyle in this confined area. Collection of actual wastewater influent from an isolated environment supporting humans is challenging. Additionally, to ensure a safe working environment in the laboratory and avoid the imposed threat of handling actual human feces, the proposed synthetic, non-human feces containing wastewater influent formulation offers an easy-to-produce and safer-to-handle option. This paper reviews several synthetic wastewater compositions that have been formulated for space exploration purposes. None of the formulations were found to be realistic nor adequate for a space-camp-type scenario. Thus, the formulation of a synthetic wastewater for simulating a wastewater influent from a human space-based camp is proposed in this paper. In addition, the physical, chemical, and biodegradation characteristics of the final formulation designed are presented to illustrate the value of the proposed influent formulation.

Removal of perfluorooctanoic acid via polyethyleneimine modified graphene oxide: Effects of water matrices and understanding mechanisms.

This research aimed to evaluate the adsorption behaviors and mechanisms of perfluorooctanoic acid (PFOA) onto polyethyleneimine modified graphene oxide (GO-PEI) from aqueous solutions. The adsorption capacity was significantly improved by doping polyethyleneimine (PEI) onto graphene oxide (GO). The Brunauer-Emmett-Teller (BET) isotherm model was considered as the best isotherm model in describing the PFOA adsorption onto GO-PEI3 (wPEI/wGO = 3). GO-PEI3 exhibited high adsorption capacity (qe = 368.2 mg/g, calculated from BET isotherm model) and excellent stability. The maximum monolayer amount of PFOA adsorption onto GO-PEI3 (qm = 231.2 mg/g) was successfully evaluated. The calculated saturated concentration (Cs = 169.9 mg/L) of PFOA on GO-PEI3 closely agrees with its critical micelle concentration (CMC = 157.0 mg/L), suggesting the formation of multilayer hemi-micelles or micelles PFOA structures on the surface of GO-PEI3. PFOA adsorption onto GO-PEI3 was inhibited by several factors including: the presence of humic acid (HA) by competing with the adsorption sites, background salts through the double-layer compression effect, and the competition from soluble ions for the amine or amide functional groups on GO-PEI3. Finally, both the FT-IR and XPS results confirmed that the adsorption of PFOA onto GO-PEI3 was through electrostatic attraction and hydrophobic interaction (physical adsorption), but not chemical adsorption. This work provides fundamental knowledge both in understanding the adsorption behavior through the BET isotherm model and in developing a stable adsorbent for PFOA adsorption. In addition, the findings highlight the potential of PFOA remediation from wastewater systems using GO-PEI in engineering applications.

Surface-bound hydroxyl radical-dominated degradation of sulfamethoxazole in the amorphous FeOOH/ peroxymonosulfate system: The key role of amorphous structure enhancing electron transfer.

In this study, activation of peroxymonosulfate (PMS) by amorphous FeOOH to degrade sulfamethoxazole (SMX) was investigated. The amorphous FeOOH showed a better performance in the decomposition of PMS and the degradation of SMX than the crystallized α-FeOOH and ß-FeOOH. The quenching experiments and EPR measurements suggested that the mechanism of PMS activation by amorphous FeOOH was mainly the surface-bound radicals (●OH and SO4●-). Basically, the surface-bound ●OH radicals were the dominate reactive oxide species in this system, which were mainly generated via the decomposition of amorphous FeOOH-PMS complexes. The degradation of SMX was significantly inhibited with the presence of H2PO4-, and this adverse impact was negligibly affected by the increase of H2PO4- concentration, implying that the inhibition of SMX degradation was caused by competitive adsorption. Consequently, the Fe-OH bonds on the amorphous FeOOH were proposed as the reactive sites for forming amorphous FeOOH-PMS complexes. Besides, the amorphous FeOOH showed a better performance in the degradation of SMX in the acid conditions than that in the base conditions due to the surface charge of amorphous FeOOH. More importantly, the reduction efficiency of Fe(III) was significantly enhanced due to the excellent conductivity of amorphous FeOOH.

Insight into the activation mechanisms of biochar by boric acid and its application for the removal of sulfamethoxazole.

Sulfamethoxazole (SMX) is frequently detected in the environment and causes a huge threaten to human health. Biochar (BC) is a metal-free adsorbent and generally exhibits a good adsorption capacity for SMX. However, the current activated methods usually result in the high energy consumption and low yield of the biochar. In this study, biochar was activated by boric acid under limited oxygen condition. The yield of biochar was increased by 103% after the activated by boric acid. The specific surface area of BC was significantly increased from 766.6 m2·g-1 to 1190.6 m2·g-1. The intensity of the (111) diamond peak of B-BC was higher than that of BC, suggesting that boric acid affected the surface pyrolysis temperature of biochar. The proposed roles of boric acid in the activation process were to: 1) enhance the generation of micropores during the pyrolysis process; 2) improve the yield of biochar via the transformation pathways of C-corresponding bonds and physical blocking. The boric acid activated biochar (B-BC) had a higher adsorption capacity for SMX than BC under the various aqueous conditions. Hence, boric acid activated biochar is a promising porous adsorbent to enhance the removal of SMX and achieve practical application.

Enhanced adsorption of perfluorooctanoate (PFOA) onto low oxygen content ordered mesoporous carbon (OMC): Adsorption behaviors and mechanisms.

The pollution of perfluorooctanoic acid (PFOA) in water bodies has been a serious threat to environment and human health. Ordered mesoporous carbons (OMCs) with different oxygen contents were prepared and first used for adsorbing PFOA from aqueous solutions. The OMC-900 with a lower oxygen content has a higher PFOA adsorption capacity than the oxygen-rich OMC-700. OMCs require a much shorter time to reach the adsorption equilibrium comparing with other adsorbents reported in literature. The mesopores play an important role in this rapid adsorption kinetics. The pseudo-second-order model better fitted the kinetic data. The multilayers adsorption was proposed for the adsorption of PFOA onto OMCs since the Freundlich isotherm model fits the experimental data well. The micelle or hemi-micelle structures may be formed during the adsorption. Various background salts showed a positive effect on PFOA adsorption due to the salting-out and divalent bridge effects. The humic acid can lead to a discernible reduction in PFOA adsorption by competing for adsorption sites on OMCs. The hydrophobic interaction and electrostatic interaction adsorption mechanisms were proposed and verified by the adsorption data. The high adsorption capacity and fast adsorption kinetics of the OMC make it a potential adsorbent for PFOA removal in engineering applications.

Synergistic adsorption and degradation of sulfamethoxazole from synthetic urine by hickory-sawdust-derived biochar: The critical role of the aromatic structure.

This study investigated the adsorptive removal and subsequent degradation of sulfamethoxazole (SMX) from a synthetic urine by biochar (BC). The BCs used in this study were prepared using two different feedstocks with different temperatures. Element analysis and Fourier transform infrared spectroscopy (FTIR) results suggested that the aromaticity of one of the BCs, 700HSBC was significantly different from the 700PSBC although both of them were prepared at the same temperature (700 °C) with similar pore size distributions and specific surface areas. Due to the presence of abundant aromatic structures, 700HSBC showed a higher SMX uptake than 700PSBC, suggesting that the π-π interaction was the main adsorption mechanism. The removal of SMX from the urine was significantly enhanced by adding hydrogen peroxide to the 700HSBC. The carbonate radicals degradation of SMX mechanism was proposed and verified. With 700HSBC having abundant aromatic structures acting as π-electron donors, it could be an efficient activator for peroxymonocarbonate (HCO4-) to generate carbonate radicals. Hence, it could be concluded that the aromatic structures on BCs play a key role in both of the adsorption and hydrogen peroxide degradation of the SMX resulting in its removal from urine.

A comparative study for phosphate adsorption on amorphous FeOOH and goethite (α-FeOOH): An investigation of relationship between the surface chemistry and structure.

Eutrophication is generally caused by excess nitrogen and phosphorus being released into surface waters by runoff. Developing adsorbents for adsorbing phosphate within soil buffer zones and/or water treatment columns may be effective methods to mitigate this problem. In this study, an amorphous FeOOH (AF) and a well-crystallized α-FeOOH (CF) was formulated to compare phosphate adsorption behavior. The physicochemical properties between these species showed significant differences in morphology, crystallization, zeta potential, and specific surface area. The AF exhibited higher phosphate uptake than CF. X-ray photoelectron spectroscopy (XPS) verified that the hydroxyl groups within AF were 13.28% higher than that in CF. The triply coordinated hydroxyl groups (µ3-OH) associated with AF and CF appeared at different positions as shown in the diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analyses, confirming that AF contains more adsorption reactive sites (µ3-OH). Mechanisms for monodentate formations and a stable six-member ring structure were proposed. The X-ray absorption near the edge structure (XANES) and XPS results suggested that the iron valence in AF was dominated by Fe (III). XANES also demonstrated that the amorphous structure found in the AF was caused by the disordered tetrahedron and octahedron alignments, leading to a higher phosphate adsorption.

Uniform Mesoporous Amorphous Cobalt-Inherent Silicon Oxide as a Highly Active Heterogeneous Catalyst in the Activation of Peroxymonosulfate for Rapid Oxidation of 2,4-Dichlorophenol: The Important Role of Inherent Cobalt in the Catalytic Mechanism.

Amorphous cobalt-inherent silicon oxide (Co-SiOx) was synthesized for the first time and employed as a highly active catalyst in the activation of peroxymonosulfate (PMS) for the rapid oxidation of 2,4-dichlorophenol (2,4-DCP). The characterization results revealed that the 0.15Co-SiOx possessed a high specific surface area of 607.95 m2/g with a uniform mesoporous structure (24.33 nm). The X-ray diffraction patterns indicate that the substituted cobalt atoms enlarge the unit cell parameter of the original SiO2, and the selected area electron diffraction pattern confirmed the amorphous nature of Co-SiOx. More bulk oxygen vacancies (Ov) existing in the Co-SiOx were identified to be one of the primary contributors to the significantly enhanced catalytic activation of PMS. The cobalt substitution both creates and stabilizes the surficial Ov and forms the adequately active Co(II)-Ov pairs which engine the electron transfer process during the catalytic activities. The active Co(II)-Ov pairs weaken the average electronegativity of Co/Si and Co/O sites, resulting in the prevalent changes in final state energy, which is the main driving cause of the binding energy shifts in the X-ray photoelectron spectroscopy (XPS) spectra of Si and O among all samples. The increase of the relative proportion of Co(III) in the spent Co-SiOx probably causes the binding energy shifts of the Co XPS spectrum compared to that of the Co-SiOx. The amorphous Co-SiOx outperforms stable and quick 2,4-DCP degradation, achieving a much higher kinetic rate of 0.7139 min-1 at pH = 7.02 than others via sulfate radical advanced oxidation processes (AOPs), photo-Fenton AOPs, H2O2 reagent AOPs, and other AOP approaches. The efficient degradation performance makes the amorphous Co-SiOx as a promising catalyst in removing 2,4-DCP or organic-rich pollutants.

The use of artificial neural network (ANN) for modeling adsorption of sunset yellow onto neodymium modified ordered mesoporous carbon.

Discharging coloring products in water bodies has degraded water quality irreversibly over the past several decades. Order mesoporous carbon (OMC) was modified by embedding neodymium(III) chloride on the surface of OMC to enhance the adsorptive removal towards these contaminants. This paper represents an artificial neural network (ANN) based approach for modeling the adsorption process of sunset yellow onto neodymium modified OMC (OMC-Nd) in batch adsorption experiments. Neodymium modified OMC was characterized using N2 adsorption-desorption isotherm, TEM micrographs, FT-IR and XPS spectra analysis techniques. 2.5 wt% Nd loaded OMC was selected as the final adsorbent for further experiments because OMC-2.5Nd showed highest removal efficiency of 93%. The ANN model was trained and validated with the adsorption experiments data where initial concentration, reaction time, and adsorbent dosage were selected as the variables for the batch study, whereas the removal efficiency was considered as the output. The ANN model was first developed using a three-layer back propagation network with the optimum structure of 3-6-1. The model employed tangent sigmoid transfer function as input in the hidden layer whereas a linear transfer function was used in the output layer. The comparison between modeled data and experimental data provided high degree of correlation (R2 = 0.9832) which indicated the applicability of ANN model for describing the adsorption process with reasonable accuracy.

Enhanced Pb(II) adsorption onto functionalized ordered mesoporous carbon (OMC) from aqueous solutions: the important role of surface property and adsorption mechanism.

Functionalized ordered mesoporous carbon (MOMC-NP) was synthesized by chemical modification using HNO3 and H3PO4 to enhance Pb(II) adsorption. The phosphate functional group represented by P-O-C bonding onto the surface of OMC was verified by FT-IR and XPS. Batch adsorption experiments revealed the improvement of adsorption capacity by 39 times over the virgin OMC. Moreover, the Pb(II) adsorption results provided excellent fits to Langmuir model and pseudo-second-order kinetic model. The adsorption mechanism of Pb(II) onto MOMC-NP revealed the formation of metal complexes with carboxyl, hydroxyl, and phosphate groups through ion exchange reactions and hydrogen bondings. The calculated activation energy was 22.09 kJ/mol, suggesting that Pb(II) adsorption was a chemisorption. At pH>pHpzc, the main Pb(II) existing species of Pb(II) and Pb(OH)+ combine with the carboxyl, hydroxyl, and phosphate functional groups via electrostatic interactions and hydrogen bonding. All these findings demonstrated that MOMC-NP could be a useful and potential adsorbent for adsorptive removal of Pb(II). Graphical abstract.

The effects of carbon disulfide driven functionalization on graphene oxide for enhanced Pb(II) adsorption: Investigation of adsorption mechanism.

The surface properties of graphene oxide (GO) have been identified as the key effects on the adsorption of Pb(II) from aqueous solutions in this study. This study reveals the effect of the surface reactivity of GO via Carbon Disulfide (CS2) functionalization for Pb(II) adsorption. After successfully preparing CS2 functionalized GO (GOCS), the specific techniques were applied to investigate Pb(II) adsorption onto GOCS. Results indicated that the new sulfur-containing functional groups incorporated onto GOCS significantly enhanced Pb(II) adsorption capacity on GOCS than that of GO, achieving an improvement of 31% in maximum adsorption capacity increasing from 292.8 to 383.4 mg g-1. The equilibrium adsorption capacity for GOCS was 280.2 mg g-1 having an improvement of 83.2% over that of 152.97 mg g-1 for GO at the same initial concentration of 150 mg L-1 under the optimal pH of 5.7. Moreover, the results of adsorption experiments showed an excellent fit to the Langmuir and Pseudo-Second-Order models indicating the monolayer and chemical adsorption, respectively. The mechanism for Pb(II) adsorption on GOCS was proposed as the coordination, electrostatic interactions, cation-pi interactions, and Lewis acid-base interactions. The regeneration study showed that GOCS had an appreciable reusability for Pb(II) adsorption with the adsorption capacity of 208.92 mg g-1 after five regeneration cycles. In summary, GOCS has been proved to be a novel, useful, and potentially economic adsorbent for the high-efficiency removal of Pb(II) from aqueous solutions.

Modeling mass transfer for adsorptive removal of Pb(II) onto phosphate modified ordered mesoporous carbon (OMC).

Phosphate modified ordered mesoporous carbon (MOMC-NP) has been synthesized and proven to be an effective adsorbent for Pb(II) removal from aqueous solutions. However, the key application components of the mass transfer operations and diffusion coefficient have not been determined. In this study, a modified Finite Bath Diffusion Control Model was mathematically developed containing a constant related to the radius of the adsorbent particle and the fractional attainment of adsorption. The adsorption experiments were conducted under various initial Pb(II) concentrations ranging from 60 mg L-1 to 100 mg L-1. The results suggested that the modified Finite Bath Diffusion Control Model was more applicable to the experimental data than the original Finite Bath Diffusion Control Model. The average value of the diffusion coefficient (λD¯) obtained from the modified finite bath diffusion control model was 1.63 × 10-2 cm2 s-1 indicating the effective diffusivity in the adsorption of Pb(II) on MOMC-NP. Overall, the modified Finite Bath Diffusion Control Model exhibited the precise description and simulation of the mass transfer kinetics for Pb(II) adsorption onto MOMC-NP. Therefore, the modified Finite Bath Diffusion Control Model could be effectively used to investigate the mass transfer kinetics of the adsorption process.

Nonpoint source pollution.

A comprehensive review of the research papers published in 2018 focusing on nonpoint source (NPS) pollution is presented in this review article. The identification of pollution from different sources and estimation of NPS pollution using various models are summarized in this review paper. Various innovative techniques are also examined to abate NPS pollution. PRACTITIONER POINTS: The non-point source pollution in 2018 is systematically reviewed and documented. This review evaluates and summarizes the identification, quantification, reduction, and management of NPS pollution. Future perspectives of NPS pollution research are discussed.

Adsorptive removal of resorcinol on a novel ordered mesoporous carbon (OMC) employing COK-19 silica scaffold: Kinetics and equilibrium study.

Phenolic compounds and their derivatives have been found in industrial wastewater, which pose threats to the natural environment. Ordered mesoporous carbon (OMC) has been identified as an ideal adsorbent possessing high specific surface area and large pore volume to alleviate these pollutants. A novel ordered mesoporous carbon was prepared using COK-19 template with the cubic Fm3m structure for the first time. Ordered mesoporous silica COK-19 was synthesized and reported in 2015. Sucrose as the carbon precursor was impregnated into the mesopores of silica and converted to carbon through carbonization process using sulfuric acid as a catalyst. Ordered mesoporous carbon was obtained after the removal of silica framework using hydrofluoric acid. Boric acid was employed for the preparation of OMCs with tunable pore sizes in the range of 6.9-16.6 nm. Several characterization techniques such as nitrogen adsorption-desorption isotherms, transmission electron microscope (TEM), Fourier transform infrared spectroscopy, Boehm titration and elemental analysis were employed to characterize the OMCs. The pore size analysis and TEM images confirmed that OMC has replicated the mesostructure of the COK-19. Results obtained from adsorption kinetics and isotherms suggest that the Pseudo-second-order model and Langmuir isotherm well described the experimental data.

Nonpoint Source Pollution.

A review of the literature published during year 2017 on topics relating to nonpoint source pollution (NPS) is presented. This article is written with a view to cater the need of nonpoint source pollution research and to summarize the new advancements in NPS control. Research developments on assessing, monitoring, and controlling the nonpoint source pollution are the main focus of this review. Future research topics related to NPS are also recommended.

Molecular simulation and experimental validation of resorcinol adsorption on Ordered Mesoporous Carbon (OMC).

Numerous research works have been devoted in the adsorption area using experimental approaches. All these approaches are based on trial and error process and extremely time consuming. Molecular simulation technique is a new tool that can be used to design and predict the performance of an adsorbent. This research proposed a simulation technique that can greatly reduce the time in designing the adsorbent. In this study, a new Rhombic ordered mesoporous carbon (OMC) model is proposed and constructed with various pore sizes and oxygen contents using Materials Visualizer Module to optimize the structure of OMC for resorcinol adsorption. The specific surface area, pore volume, small angle X-ray diffraction pattern, and resorcinol adsorption capacity were calculated by Forcite and Sorption module in Materials Studio Package. The simulation results were validated experimentally through synthesizing OMC with different pore sizes and oxygen contents prepared via hard template method employing SBA-15 silica scaffold. Boric acid was used as the pore expanding reagent to synthesize OMC with different pore sizes (from 4.6 to 11.3 nm) and varying oxygen contents (from 11.9% to 17.8%). Based on the simulation and experimental validation, the optimal pore size was found to be 6 nm for maximum adsorption of resorcinol.

Methanogenesis under acidic pH conditions in a semi-continuous reactor system.

Operating an anaerobic digester at low pH could offer several advantages over operation at neutral pH. Most wastewater streams targeted for anaerobic digestion are inherently acidic, requiring alkalinity supplementation (at added expense) to buffer the pH at neutral. Additionally, previously published work completed by the authors using batch systems suggested that lowering the system pH could increase methane production by as much as 30%. The goal of this research was to evaluate the feasibility of sustaining methanogenesis at low pH in a semi-continuous laboratory-scale fermentor. Significant methane production was achieved in a system ranging in pH from approximately 4.0-5.3. Results show that, if the consortium is allowed to sufficiently acclimate to acidic conditions, methanogenesis can be maintained under acidic pH conditions, resulting in overall chemical oxygen demand (COD) reduction and methane production comparable to that achieved in a neutral pH system.