Clean and efficient synthesis of LiFePO4 cathode material using titanium white waste and calcium dihydrogen phosphate.

Large amounts of titanium white waste are generated in the production of titanium dioxide using sulphate method, which in turn can be used to prepare LiFePO4 cathode material, thereby reducing environmental risks and achieving resource recovery. However, a key challenge lies in the elimination of impurities. In this work, a cost-efficient and straightforward approach based on phase transformation during hydrothermal treatment was proposed to utilize titanium white waste with calcium dihydrogen phosphate for the preparation of LiFePO4 cathode material. The content of Fe in the leachate was enriched to 81.5 g/L after purification, while 99.9 % of Ti and 98.36 % of Al and were successfully removed. In the subsequent process for Fe/P mother liquor preparation, the losses of Fe and P were only 5.82 % and 2.81 %, respectively. The Fe and P contents of the synthesized FePO4 product were 29.47 % and 17.08 %, respectively, and the Fe/P molar ratio was 0.986. Crystal phase of the product matched well with standard iron phosphate, and the lamellar microstructure of FePO4 was uniform with the particle size ranging from 3 to 5 µm. Moreover, the contents of impurities in the product were far below the standard. The initial discharge of LiFePO4 synthesized by the iron phosphate was 160.6 mAh.g-1 at 0.1C and maintained good reversible capacity after 100 cycles. This work may provide new strategy for preparing LiFePO4 cathode material from industrial solid waste.

Recovery of iron and aluminum from iron-rich bauxite residue by an integrated phase reconstruction approach.

The comprehensive recovery of iron and aluminum from iron-rich bauxite residue (IRBR) is of critical importance both in terms of resource utilization and environment protection, which, however, is challenging due to the intertwined phases between Iron and aluminum. In this study, an integrated phase reconstruction approach, consisting of alkali roasting, two-stage column leaching, and carbonation decomposition, was proposed for Fe/Al recovery from IRBR. The results demonstrated that aluminum and sodium were fused into soluble substances such as sodium aluminate (Na7Al3O8, NaAlO2, and Na2O (Al2O3)11) in the alkali roasting process, allowing for the separation of Al and Fe in the subsequent leaching process. Following water/FeCl3 solution leaching, the removal efficiency of aluminum reached 84.66%, and Fe content in the residue could be enriched to 55.56%. Fe can be recycled as iron concentrate, and Al in the leaching solution with 75.95 g/L can be recovered in the form of Al(OH)3 through carbonation decomposition. This work provides an alternative strategy for the recovery of resources from IRBR, with potential implications for the sustainable development of the aluminum industry.

Coordination-driven Cu-based Fenton-like process for humic acid treatment in wastewater.

Fenton oxidation process is effective in organic pollutant degradation during wastewater treatment, but subject to narrow pH range and secondary pollution. In this work, an application-promising alternative, i.e., coordination-driven Cu-based Fenton-like process, was proposed for wastewater treatment using humic-acid (HA) as the target contaminant. The results showed that the removal of HA through Cu-based Fenton-like process can reach 70% under the condition of pH 8.0, 146.8 mmol/L H2O2, 146.8 µmol/L Cu (II), 50 °C, and 4 h. Addition of Cl- could significantly accelerate the reaction process through coordination with copper ions, while HCO3- and P2O74- exhibited opposite effects. Increasing temperature is also beneficial for advancing the reaction, and the removal of HA followed pseudo-first-order kinetics. Fluorescence spectroscopic analyses showed that the removal of HA experienced a two-stage process, i.e., oxidation followed by degradation, which is dependent of the presence of coordination ions. Parallel factor analysis was used to characterize the change of fluorescence components. Three fluorescent components, i.e., terrestrial humic-like, UV/visible terrestrial humic-like and protein-like component were identified, all of which were effectively removed. This study deepens our understanding on Cu-based Fenton-like process, and may provide a promising technology for refractory wastewater treatment.

Aluminum separation by sulfuric acid leaching-solvent extraction from Al-bearing LiFePO4/C powder for recycling of Fe/P.

Recovery of battery-grade FePO4 from Al-bearing spent LiFePO4 batteries (LFPs) is important for both prevention of environmental pollution and recycling of resources for LFPs industries. The premise for FePO4 recovery from spent LFPs is the separation of Al, because Al readily co-precipitates with FePO4 and lowers the electrochemical performance of the regenerated LiFePO4. In this work, an efficient approach involving sulfuric acid leaching followed by solvent extraction was developed to separate Al from spent LiFePO4/C powder. Di-(2-ethylhexyl) phosphoric acid (D2EHPA) in sulfonated kerosene was used as the extractant. The results showed that 96.4% of aluminum was extracted while the loss of iron was only 1.1% under the optimal conditions. The mass fraction of Al in the iron phosphate obtained from the extraction raffinate was only 0.007%, meeting the standard for preparing battery-grade FePO4. The extracted Al can be easily stripped by diluted H2SO4 solution and the extractants can be reused. Additionally, slope analysis method, FTIR spectroscopy, and ESI-MS analysis revealed that the extraction of Al in D2EHPA can be ascribed to the ion exchange between hydrogen ion of -PO(OH) and Al3+. This work may provide an economically feasible method for the recycling of valuable components from spent Al-bearing LiFePO4/C powder.

Preparation of Battery-Grade FePO4·2H2O Using the Stripping Solution Generated from Resource Recycling of Bauxite Residue.

A novel process for the high-value-use of iron from bauxite residue was proposed in this work. The process was trying to use the iron-containing stripping solution generated during resource recycling of bauxite residue to produce battery-grade FePO4·2H2O product. Thermodynamics calculation indicates that Fe and P in the stripping solution mainly existed in the form of FeHPO4+, and the theoretical pH for the conversion reaction from FePO4·2H2O to Fe(OH)3 was 1.72. The optimal condition for the synthesis of FePO4·2H2O using the stripping solution was determined as: reaction pH of 0.8, reaction temperature of 90°C, Fe/P ratio of 1, and reaction time of 24 h. XRD result showed that the synthesized FePO4·2H2O was well-crystallized and perfectly matched with the characteristic peaks of FePO4·2H2O. Moreover, all the parameters of the synthesized iron phosphate meet the quality requirements of battery precursor.

Characterization and treatment of landfill leachate: A review.

Landfill leachate is a complicated organic wastewater generated in the sanitary landfilling process. Landfill leachate must be appropriately disposed to avoid ecotoxicity and environmental damage. An in depth understanding of the physiochemical characteristics and environmental behaviors of landfill leachate is essential for its effective treatment. In this study, recent advances on the properties of landfill leachate, its characterization methods and treatment techniques are critically reviewed. Specifically, the up-to-date spectroscopic techniques for landfill leachate characterization and advanced oxidation treatment techniques are highlighted. Moreover, the drawbacks and challenges of current techniques for landfill leachate characterization and treatment are discussed, along with the future perspectives in the development of characterization and treatment approaches for landfill leachate.

Separation and recovery of arsenic from As, Cu, and Zn rich leaching liquor using a reduction-crystallization approach.

As, Cu, and Zn rich leaching liquor is generated in the leaching process of copper dust, which contains various metals with high recovery value. Herein, an approach for the direct separation and recovery of arsenic from As, Cu, and Zn rich leaching liquor was proposed. The approach includes two steps, namely SO2 reduction and arsenic crystallization. The factors affecting the reduction of As(v) to As(iii) were investigated, including the pH, SO2 dosage, and reduction temperature. In the crystallization stage, the impacts of sulfuric acid consumption and temperature on the crystallization of arsenic (As2O3) were studied. The results show that the optimal H+ concentration, temperature, and SO2 input for the arsenic reduction were 3.95 mol L-1, 45 °C, and 1.14 L g-1 As(v), respectively. While the optimal temperature and sulfuric acid dosage in As recovery process were 5 °C and 0.1 L L-1 leaching liquor, respectively. Under these conditions, the As2O3 recovery percentage reached 96.53%, and the losses of Cu and Zn were only 3.12% and 0.75%, respectively. The precipitate contained 96.72% of As2O3, 0.83% of Cu, and 0.13% Zn. Compared with the traditional technologies, this new method can improve the recovery efficiency of As2O3 and reduce the loss percentage of other valuable metals (Cu and Zn).

Degradation characteristics of dissolved organic matter in nanofiltration concentrated landfill leachate during electrocatalytic oxidation.

Nanofiltration concentrated landfill leachate (NCLL) is produced during the integration process of biodegradation and nanofiltration, containing a large amount of recalcitrant dissolved organic matter (DOM). In this work, electrocatalytic oxidation technology was employed to degrade DOM in NCLL and spectroscopic technology was applied to explore the structural changes. The results showed that under the optimal experimental condition (pH = 2.0, NaCl concentration = 0.7%, Fe2(SO4)3 concentration = 0.8%, the retention time = 6 h), the removal rates of COD, TOC, and UV254 were 99.0%, 57.4%, 99.3% respectively. Ultraviolet-Visible (UV-Vis) spectral analysis showed that aromatic CC can be effectively degraded by electrocatalytic oxidation, resulting in decreases of aromaticity and molecular weight in NCLL. Two fluorescent components (terrestrial humic-like substances and fulvic-like substances) were identified in NCLL by parallel factor analysis, which can be effectively removed by electrocatalytic oxidation with removal rates of 99.9% and 90.5%, respectively. In addition, through two-dimensional correlation spectroscopic analysis, the sequence of structural changes of the DOM in NCLL was confirmed: unsaturated double bonds → fulvic-like components/aromatic structures → terrestrial humic-like components. These spectral characterization techniques can provide a deep understanding of the degradation pathways of DOM and provide new insights for the treatment of NCLL.

Spectroscopic response of soil organic matter in mining area to Pb/Cd heavy metal interaction: A mirror of coherent structural variation.

Understanding the interaction between heavy metals and soil organic matter (SOM) in mining area is important for the clarification of the environmental behaviors of heavy metals. In this work, the coherence of structural changes of SOM during interaction with Pb2+ and Cd2+ ions were examined by using UV-vis/fluorescence spectroscopy coupled with correlation analyses. The result showed that phenolic- and carboxylic-like groups of SOM were engaged in the complexation of heavy metals (Pb2+ and Cd2+) with SOM, resulting in the formation of highly conjugated macromolecules/aggregates and an increase in molecular weight/size. Fluorescent humic-like, fulvic-like, and protein-like species were involved in the binding with Pb2+/Cd2+ ions, which were closely correlated with phenolic-like and carboxylic-like constitutes. SOM was more favorable to bind with Pb2+ ions than Cd2+ ions, with a less susceptive of SOM structure to Pb2+/Cd2+ ions in the mining area compared to those off the mining area under heavy metal stress. These results may provide a new insight for the treatment and remediation of heavy metal-polluted soil in mining area.

Arsenic removal from highly-acidic wastewater with high arsenic content by copper-chloride synergistic reduction.

A synergistic combination of chloride and copper powder was proposed as a new method to reductively remove arsenic from highly-acidic wastewater with high arsenic content (HAWA). As(III) was reduced to As(0) by copper powder in the presence of chloride and were effectively removed from HAWA. The procedure to remove arsenic was optimized as follows: initial H+ concentration of 5 mol L-1, Cu-to-As molar ratio of 8, Cl-to-As molar ratio of 10, a reaction temperature of 60 °C, copper powder particle size of 68-24 µm, and a stirring speed of 300 r min-1. Under these optimal conditions, the removal rate of arsenic was close to 100%. Kinetics results suggested that the arsenic removal process was controlled by both diffusion and chemical reactions with an apparent activation energy of 29.78 kJ mol-1. The XRD results showed that the removed arsenic in the residue existed primarily in the form of AsCu3 alloy.

Elucidating the structural variation of membrane concentrated landfill leachate during Fenton oxidation process using spectroscopic analyses.

Membrane concentrated landfill leachate (MCLL) contains large amounts of recalcitrant organic matter that cause potential hazards to the environment. Knowledge on the compositional variation of MCLL during treatment is important for a better understanding on the degradation pathway of organic pollutants. In this work, the structural change of MCLL during Fenton oxidation process was examined using spectroscopic techniques. The removal rates of COD, TOC and UV254 reached 78.9 ±â€¯1.3%, 70.2 ±â€¯1.4% and 90.64 ±â€¯1.6%, respectively, under the optimal condition (i.e., dosage of H2O2 = 9.0 mL/200 mL, H2O2/Fe(II) molar ratio = 3.0, pH = 3.0, time = 40 min). Spectral analyses suggested that aromatic/CC structure and CO bonds in MCLL can be successfully destroyed by Fenton oxidation, resulting in a decrease in molecular weight. One fulvic-like and one humic-like components were identified in MCLL, both of which can be removed by Fenton treatment. In addition, two-dimensional correlation spectroscopic analyses suggested the oxidative changes of MCLL structure in the order of fulvic-like component/unsaturated conjugated bond > aromatic structure > humic-like component. The results may provide a new insight to the understanding on the structure variation of MCLL during treatment, which is beneficial for the design of cost-effective treatment strategies.

Removal of ammonia-nitrogen in wastewater using a novel poly ligand exchanger-Zn(II)-loaded chelating resin.

In this study, a novel poly ligand exchanger-Zn(II)-loaded resin was designed to effectively remove ammonia-nitrogen (NH3-N) from wastewater. The surface morphology and structure of the Zn-loaded resin were characterized using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR), respectively. SEM shows the surfaces of the Zn(II)-loaded resin were rough and nonporous and EDS demonstrated that Zn2+ was loaded onto the resin successfully. In addition, the combination form of Zn(II) with NH3-N adsorption reagent was revealed by FTIR spectra; the complex could be R-N-R-O-Zn-O-R-N-R and R-N-R-(O-Zn)2. The kinetics and equilibrium of the NH3-N adsorption onto the Zn(II)-loaded resin has been investigated. The effects of pH, reaction time, and temperature on NH3-N removal from wastewater by Zn(II)-loaded resin were investigated, and the results showed that the maximum adsorption capacity reached 38.55 mg/g at pH 9.54 at 298 K in 240 min. The adsorption ability of the modified resin decreased with an increase in temperature. Moreover, the NH3-N adsorption followed a pseudo-second-order kinetic process. The kinetic data demonstrated that the adsorption process might be limited by a variety of mechanisms. The study can provide the scientific foundation for the extensive application of a novel poly ligand exchanger-Zn(II)-loaded resin to remove NH3-N from wastewater.

Experimental study of paraffin melting in cylindrical cavity with central electric heating rod.

The experimental study for the melting processes of phase change material (paraffin) inside a cylindrical container under different boundary conditions of the cylindrical outside surface was carried out. In the experiments paraffin was heated by the heating rod installed in the center of the cylindrical container. The interpolation method was employed to calculate phase front and liquid fraction during the melting process by the reading of the thermocouples in an array arrangement. Paraffin near the heating rod firstly melted due to heat conduction in the initial melting stage, and then the generation and intensification of natural convection led to the acceleration of phase changes, resulting in obvious temperature stratifications in the upper region of the cylinder container. Moreover, flat temperature phenomena are described and discussed in detail. The effect of different heating powers, boundary conditions and the temperatures of water bath on melting rates is evaluated as well.

Inherited macular degeneration-associated mutations in CNGB3 increase the ligand sensitivity and spontaneous open probability of cone cyclic nucleotide-gated channels.

Cyclic nucleotide gated (CNG) channels are a critical component of the visual transduction cascade in the vertebrate retina. Mutations in the genes encoding these channels have been associated with a spectrum of inherited retinal disorders. To gain insight into their pathophysiological mechanisms, we have investigated the functional consequences of several CNGB3 mutations, previously associated with macular degeneration (Y469D and L595F) or complete achromatopsia (S156F, P309L, and G558C), by expressing these subunits in combination with wild-type CNGA3 in Xenopus oocytes and characterizing them using patch-clamp recordings in the inside-out configuration. These mutations did not prevent the formation of functional heteromeric channels, as indicated by sensitivity to block by L-cis-diltiazem. With the exception of S156F, each of the mutant channels displayed electrophysiological properties reflecting enhanced channel activity at physiological concentrations of cGMP (i.e., a gain-of-function phenotype). The increased channel activity produced by these mutations resulted from either increased functional expression levels, or increased sensitivity to cyclic nucleotides. Furthermore, L595F increased the spontaneous open probability in the absence of activating ligand, signifying a ligand independent gain-of-function change. In addition to the CNGB3 disease-associate mutations, we characterized the effects of several common CNGB3 and CNGA3 single-nucleotide polymorphisms (SNPs) on heteromeric CNGA3+CNGB3 channel function. Two of the SNPs examined (A3-T153M, and B3-W234C) produced decreased ligand sensitivity for heteromeric CNG channels. These changes may contribute to background disease susceptibility when combined with other genetic or non-genetic factors. Together, these studies help to define the underlying molecular phenotype for mutations relating to CNG channel disease pathogenesis.

Two structural components in CNGA3 support regulation of cone CNG channels by phosphoinositides.

Cyclic nucleotide-gated (CNG) channels in retinal photoreceptors play a crucial role in vertebrate phototransduction. The ligand sensitivity of photoreceptor CNG channels is adjusted during adaptation and in response to paracrine signals, but the mechanisms involved in channel regulation are only partly understood. Heteromeric cone CNGA3 (A3) + CNGB3 (B3) channels are inhibited by membrane phosphoinositides (PIP(n)), including phosphatidylinositol 3,4,5-triphosphate (PIP(3)) and phosphatidylinositol 4,5-bisphosphate (PIP(2)), demonstrating a decrease in apparent affinity for cyclic guanosine monophosphate (cGMP). Unlike homomeric A1 or A2 channels, A3-only channels paradoxically did not show a decrease in apparent affinity for cGMP after PIP(n) application. However, PIP(n) induced an ∼2.5-fold increase in cAMP efficacy for A3 channels. The PIP(n)-dependent change in cAMP efficacy was abolished by mutations in the C-terminal region (R643Q/R646Q) or by truncation distal to the cyclic nucleotide-binding domain (613X). In addition, A3-613X unmasked a threefold decrease in apparent cGMP affinity with PIP(n) application to homomeric channels, and this effect was dependent on conserved arginines within the N-terminal region of A3. Together, these results indicate that regulation of A3 subunits by phosphoinositides exhibits two separable components, which depend on structural elements within the N- and C-terminal regions, respectively. Furthermore, both N and C regulatory modules in A3 supported PIP(n) regulation of heteromeric A3+B3 channels. B3 subunits were not sufficient to confer PIP(n) sensitivity to heteromeric channels formed with PIP(n)-insensitive A subunits. Finally, channels formed by mixtures of PIP(n)-insensitive A3 subunits, having complementary mutations in N- and/or C-terminal regions, restored PIP(n) regulation, implying that intersubunit N-C interactions help control the phosphoinositide sensitivity of cone CNG channels.

The recycling of Mn-Zn ferrite wastes through a hydrometallurgical route.

A novel recycling route using acid leaching, reduction, purification, co-precipitation and traditional ceramic process was applied to process the Mn-Zn ferrite wastes and prepare the corresponding high permeability soft magnetic product. Above 95% of Fe, Mn, Zn in the waste materials could be recycled in the form of Mn-Zn ferrite products through the hydrometallurgical route. The comprehensive properties of Mn-Zn ferrite prepared from wastes by this route have broader frequency characteristics, higher resistivity, lower loss coefficient and temperature coefficient as compared to the A102 product (Acme Electronics Corporation, Taiwan). Moreover, the cost of this recycling technology has economical advantage over the traditional ceramic process, which holds a promising industrial application.

Recovery of zinc from hyperaccumulator plants: Sedum plumbizincicola.

Hyperaccumulator biomass harvested after heavy-metal phytoremediation must be considered as hazardous waste that should be contained or treated appropriately before disposal or reuse. As a potential method to detoxify the biomass and to convert this material to a suitable fertilizer or mulch, leaching of heavy metals from Sedum plumbizincicola biomass was studied by using ammonia-ammonium chloride solution as a leaching agent. The research was carried out in two phases: (i) a leaching study to determine the heavy metal:zinc extraction efficiency of this leaching agent and (ii) a thermodynamic analysis to identify the likely reactions and stable Zn(II) species formed in the leaching systems. Experimentally, a Taguchi orthogonal experiment with four variable parameter elements: leaching temperature, nNH4Cl:nNH3 ratio, leaching time and solid-liquid ratio, each at three levels, was used to optimize the experimental parameters by the analysis of variances. Application of the Taguchi technique significantly reduced the time and cost required for the experimental investigation. The findings indicate that leaching temperature had the most dominant effect on metal extraction performance, followed by nNH4Cl:nNH3 ratio, solid-liquid ratio and leaching time. Accordingly, the optimum leaching conditions were determined as temperature: 60 degrees C, nNH4Cl:nNH3 = 0.6, leaching time: 2 h and solid/liquid ratio: 5:1. The total zinc removal after leaching under the optimum conditions reached 97.95%. The thermodynamic study indicated that the dominant species produced by the leaching process should be the soluble species Zn(NH3)4(2+).

Study on the preparation of Mn-Zn soft magnetic ferrite powders from waste Zn-Mn dry batteries.

Using waste Zn-Mn dry batteries, waste scrap iron and pyrolusite as raw materials, Mn-Zn soft magnetic ferrite powders were prepared through the process of simultaneous leaching, purification and co-precipitation. The experimental results indicated that the leached yields of Fe, Mn and Zn were 92.02%, 96.14% and 98.34%, respectively. The leached liquor was purified through these processes of sulfuration precipitation, fluorination precipitation and double salt precipitation deep purification process. Therefore, high removal yields of impurities could be achieved. Removal yields were as follows: Ca 99.7%, Mg 92.33%, Al 96.48%, Si 63.64%, Cu 99.86%, Pb 98.51%, Cd 53.0% and Ni 78.72%. Among these co-precipitation powders, the average mass content of the main components were Fe 41.41%, Mn 13.92% and Zn 4.49%, and the mass ratio of Fe:Zn:Mn was 69.2:23.3:7.5. Compared with the theoretical prescription (Fe:Mn:Zn=67.3:24.4:8.3), the absolute errors of main components were Fe +1.9%, Mn -1.1% and Zn -0.8%. Because of content impurities in co-precipitation powders (Ca<0.0028%, Mg<0.0053%, Al<0.0084%, SiO(2)<0.0023%, Pb<0.0031% and Cu<0.0010%), the qualities of these gained co-precipitation powders could compete with the demand for the preparation of soft magnetic ferrite. The magnetic properties also demonstrated that the soft magnetic ferrite samples, which were made from the co-precipitation powders prepared by used batteries, had the same qualities as PC30 made by the TDK Company.

Subunit configuration of heteromeric cone cyclic nucleotide-gated channels.

Cone photoreceptor cyclic nucleotide-gated (CNG) channels are thought to be tetrameric assemblies of CNGB3 (B3) and CNGA3 (A3) subunits. We have used functional and biochemical approaches to investigate the stoichiometry and arrangement of these subunits in recombinant channels. First, tandem dimers of linked subunits were used to constrain the order of CNGB3 and CNGA3 subunits; the properties of channels formed by B3/B3+A3/A3 dimers, or A3/B3+B3/A3 dimers, closely resembled those of channels arising from B3+A3 monomers. Functional markers in B3/B3 (or A3/A3) dimers confirmed that both B3 subunits (and both A3 subunits) gained membership into the pore-forming tetramer and that like subunits were positioned adjacent to each other. Second, chemical crosslinking and co-immunoprecipitation studies using epitope-tagged monomer subunits both demonstrated the presence of two CNGB3 subunits in cone channels. Together, these data support a preferred subunit arrangement for cone CNG channels (B3-B3-A3-A3) that is distinct from the 3A:1B configuration of rod channels.

Achromatopsia-associated mutation in the human cone photoreceptor cyclic nucleotide-gated channel CNGB3 subunit alters the ligand sensitivity and pore properties of heteromeric channels.

Cone photoreceptor cyclic nucleotide-gated (CNG) channels are thought to form by assembly of two different subunit types, CNGA3 and CNGB3. Recently, mutations in the gene encoding the CNGB3 subunit have been linked to achromatopsia in humans. Here we describe the functional consequences of two achromatopsia-associated mutations in human CNGB3 (hCNGB3). Co-expression in Xenopus oocytes of human CNGA3 (hCNGA3) subunits with hCNGB3 subunits containing an achromatopsia-associated mutation in the S6 transmembrane domain (S435F) generated functional heteromeric channels that exhibited an increase in apparent affinity for both cAMP and cGMP compared with wild type heteromeric channels. In contrast, co-expression of a presumptive null mutation of hCNGB3 (T383f.s.Delta C) with hCNGA3 produced channels with properties indistinguishable from homomeric hCNGA3 channels. The effect of hCNGB3 S435F subunits on cell-surface expression of green fluorescent protein-tagged hCNGA3 subunits and of non-tagged hCNGA3 subunits on surface expression of green fluorescent protein-hCNGB3 S435F subunits were similar to those observed for wild type hCNGB3 subunits, suggesting that the mutation does not grossly disturb subunit assembly or plasma membrane targeting. The S435F mutation was also found to produce changes in the pore properties of the channel, including decreased single channel conductance and decreased sensitivity to block by l-cis-diltiazem. Overall, these results suggest that the functional properties of cone CNG channels may be altered in patients with the S435F mutation, providing evidence supporting the pathogenicity of this mutation in humans. Thus, achromatopsia may arise from a disturbance of cone CNG channel gating and permeation or from the absence of functional CNGB3 subunits.