Bipolar-membrane electrodialysis polishing step for antimony, arsenic, and bismuth separation — reserved filing

This asset represents a reserved downstream polishing step within the broader antimony-thioglycolate process family in Lattice Graph's critical-mineral recovery and recycling separations portfolio. The core commercial premise is straightforward: thio-carboxylate leach chemistry selectively dissolves antimony, arsenic, and bismuth from complex feeds, but a leachate containing all three elements still requires a separation stage before individual metal streams can be recovered at commercially useful purities. Bipolar-membrane electrodialysis (BPMED) is a membrane-electrochemical technology that can simultaneously split water into acid and base while driving ionic species across selective membranes, making it a natural candidate for separating metal species that differ in their ionic charge, speciation, and complexation behavior in thioglycolate or thio-carboxylate media. The timing logic is defensive and optionality-preserving rather than speculative. The parent provisional on the antimony-thioglycolate process is the commercial center of gravity; this filing slot exists because patent counsel identified BPMED as a technically coherent downstream embodiment that, if left unclaimed, could be adopted independently by a competitor to erode the exclusionary perimeter around the leach process itself. By expressly reserving this embodiment in the parent application — with priority position intact — the portfolio preserves the right to file a full, substantively claimed patent on the BPMED step without incurring a prior-art date penalty, while avoiding the obligation to disclose and defend the full process details until bench-scale data are in hand. For a prospective acquirer or licensee, this asset should be understood as a strategic placeholder with genuine technical merit but no standing claims, no completed computational validation, and no published bench data. Its value is the priority date preservation and the architectural coherence it adds to what would otherwise be a leach-only position. A buyer of the parent process family gets this reserved slot as part of the package; evaluated in isolation, it is an option on a future patent rather than a patent itself.

The material system in question is not a crystalline solid but a composite electrochemical membrane architecture: a sulfonated polyaromatic bipolar membrane arranged in a multi-compartment electrodialysis stack. In BPMED, a bipolar membrane consists of a cation-exchange layer laminated to an anion-exchange layer; when current is applied in reverse bias, water dissociation at the junction generates protons and hydroxide ions that acidify or basify adjacent compartments without adding salt. The "sulfonated polyaromatic" descriptor refers to the cation-exchange layer chemistry — aromatic backbones such as poly(ether sulfone) or poly(arylene ether ketone) bearing pendant sulfonate groups, which confer high proton conductivity and chemical resistance to the mildly reducing, sulfur-containing leachate environment. The fixed-site polyvalent-cation loading mentioned in the reserved embodiment description — citing Sb, Bi, Zr, Ti, Sn, and Ce as candidate fixed-site species — is a membrane-functionalization strategy intended to create selective binding or exclusion sites for target oxyanions or cationic metal complexes, a concept with literature precedent in heavy-metal-selective membranes but not yet demonstrated in the specific context of thioglycolate-complexed Sb/As/Bi streams. The electrochemical separation challenge here is non-trivial. Antimony, arsenic, and bismuth, when leached in thio-carboxylate media, exist as a mixture of anionic thio-complexes (e.g., Sb(SCH₂COO)₄³⁻ type species), neutral species, or low-charge cationic species depending on pH, oxidation state, and ligand-to-metal ratio. Arsenic(III) and arsenic(V) have markedly different speciation from antimony(III) and bismuth(III) under the same conditions. The BPMED design premise is that compartment acidification can shift speciation toward differentially mobile forms, while fixed-site cation loading in the membrane matrix can impose an additional selectivity layer — but the actual transport numbers, membrane permeability coefficients, and current-efficiency figures for these specific species in this specific medium have not been measured or simulated within this filing. The mention of Zr, Ti, Sn, and Ce as fixed-site options reflects awareness of the hydrolytic affinity of these metal oxides for arsenic and antimony oxyanions, which is documented in the water-treatment literature, but extrapolation to BPMED membrane design in a thio-carboxylate feed is a genuinely open engineering question. Because this is a reserved embodiment rather than a prosecuted claim, Lattice Graph's standard multi-layer computational validation protocol — running candidate structures through MACE, CHGNet, MatterSim, and ORB interatomic potentials, requiring consensus on phonon stability, then advancing to targeted DFT simulations for dielectric response, migration barriers, or adsorption energies — has not been applied here. BPMED systems are not amenable to the same crystal-structure stability screens used for solid-state materials; the relevant computational work would instead involve molecular-dynamics simulations of polymer membrane transport, solvation-shell calculations for metal-thio complexes at the membrane interface, and possibly grand-canonical Monte Carlo for sorption selectivity. None of this simulation work is reported as completed. The asset stands at the conceptual disclosure stage: the chemistry is physically plausible, the membrane family is established industrially (companies such as Fumatech and Astom manufacture commercial BPMED stacks), and the application to Sb/As/Bi polishing is a logical extension — but the quantitative performance case remains to be built. What is computationally and experimentally established in the parent family — the antimony-thioglycolate leach itself — provides the upstream context that makes this downstream step meaningful. If the leach selectively extracts Sb, As, and Bi into a sulfur-ligand-stabilized pregnant leach solution, any separation stage operating on that defined feed chemistry has a more tractable engineering problem than a generic polymetallic leachate. That feed-definition advantage is the technical inheritance this reserved embodiment receives from the parent process, and it is the most important framing point for any technical due diligence team reviewing this asset.

The addressable market for Sb/As/Bi separation sits at the intersection of critical-mineral supply-chain security and secondary-resource recovery. Antimony is a European Union and United States Government-designated critical mineral with a highly concentrated primary supply: China accounts for roughly 50-60% of global mine production, and geopolitical supply risk has accelerated interest in both primary diversification and secondary recovery from complex polymetallic concentrates, smelter residues, and electronic waste. Global antimony consumption runs in the range of 100,000-150,000 metric tons per year (as an estimate based on publicly available industry reports), with demand anchored in flame retardants, lead-acid battery alloys, and emerging applications in antimony-based battery chemistries. Bismuth, though smaller in volume, commands premium pricing as a lead replacement in solders and pharmaceuticals. Arsenic, while not commercially recovered at scale, requires separation and safe disposition in virtually every antimony or copper smelting operation, imposing a cost that a selective separation process could reduce. A BPMED polishing step would be sold or licensed as a modular downstream unit operation, bolted onto an existing leach circuit rather than replacing the front end. The licensing logic therefore follows a process-technology model: royalty on throughput or per-unit-of-metal-recovered, or an equipment-embedded license if Lattice Graph or a partner supplies the stack hardware. The capital cost of BPMED systems is generally lower than solvent-extraction circuits for equivalent throughput, and the reagent footprint is smaller (bipolar membranes generate acid and base in situ rather than requiring external chemical addition), which makes the technology attractive for modular or remote-site deployment — a relevant consideration for artisanal and small-scale mining operations that handle antimony-rich feeds in Southeast Asia, West Africa, and Latin America. Estimating a royalty-bearing market size for this specific embodiment is premature given that no commercialized BPMED Sb/As/Bi process currently exists; the opportunity is better framed as a process-licensing premium on the parent antimony-thioglycolate family rather than a standalone revenue line.

downstream Sb/As/Bi polishing option preserved for a separate filing

reserved; option preserved without prejudice to priority

The natural buyers for this asset are companies that have already decided to acquire or license the parent antimony-thioglycolate leach technology and want to control the full process train from leach to purified metal streams. That set includes specialty-metals processors with antimony, bismuth, or complex sulfide concentrate operations — particularly those investing in reduced-acid, lower-footprint hydrometallurgical alternatives to pyrometallurgical smelting. Battery-materials companies building domestic antimony supply chains for antimony-sulfide or antimony-oxide battery applications would have strategic motivation to lock up the full process IP, including reserved downstream steps, to prevent a future blocking position from a third party. Mining royalty companies or technology holding entities assembling critical-mineral processing IP portfolios for licensing would also find value in the priority-date preservation, provided they are prepared to fund the bench-validation program needed to convert the reservation into a prosecutable application. A buyer purchasing only this reserved embodiment in isolation would find limited immediate utility — there are no claims to enforce, no data to license, and the membrane technology itself (excluding the specific application to thioglycolate media) is not novel. The asset's value is inseparable from the parent family, and any commercial conversation should position it as a component of a broader process-technology transaction covering the leach chemistry and any other downstream processing steps in the critical-mineral recovery and recycling separations portfolio.

The primary risk is straightforward: this is an unfiled, unclaimed embodiment with no bench data. If the portfolio is acquired and the buyer does not fund the validation program and follow-on filing within the window available before priority lapses or the provisional's disclosure is exhausted, the priority position is permanently lost. A competitor who independently develops and files a BPMED Sb/As/Bi process on the basis of published academic literature — which does exist for related applications — could establish an intervening priority date that forecloses or narrows what Lattice Graph's future filing can claim. The risk is manageable but time-sensitive. The technical de-risking roadmap has three steps: first, synthesize and characterize a sulfonated polyaromatic membrane with candidate fixed-site loadings using antimony-oxide or bismuth-oxide nanoparticles embedded in the matrix; second, conduct bench-scale BPMED experiments on a synthetic thio-carboxylate Sb/As/Bi leachate to measure separation factors, current efficiency, and membrane stability over extended operation; third, draft and file the dedicated application with claims grounded in the resulting data. Parallel FTO analysis of the specific membrane compositions and operating parameters should accompany step two. The program is resource-intensive but technically well-scoped, and the existence of established BPMED hardware suppliers means that stack procurement is not a development bottleneck. The commercial risk — whether the antimony market and the specific leach-to-BPMED process economics justify the investment — depends primarily on the parent leach process's commercial traction, not on this reserved embodiment's standalone merits.