Chinese exporters ship cobalt sulfate heptahydrate (CoSO4·7H2O, CAS 10026-24-1, EINECS 600-050-9) at industrial purity ≥99% with Co content 20-21% min, packed in 25kg bags with 50kg drum and 1,000kg jumbo options [S4]. Hubei Tao Yuan Chemical lists a 100,000 mt/year capacity, MOQ 1 ton, ≤4.87h average response, and FOB/CIF/CFR/EXW Incoterms from Tianjin, Shanghai, and Guangzhou ports [S4].
Feed-grade lots are governed by HG/T 3775-2005, requiring Co ≥33% (monohydrate) or ≥20% (heptahydrate), Pb ≤0.001-0.002%, As ≤0.0005%, and ≥95% pass through 280μm and 800μm test sieves [S1]. The same molecule under technical or battery grade carries different ceilings, with battery-grade Ni 10ppm max, Pb 10ppm max, and As 10ppm max in one supplier's three-tier table [S2].
Forms, CAS numbers, and core physical constants
Cobalt sulfate is traded mainly as the heptahydrate CoSO4·7H2O (CAS 10026-24-1, MW 281.10) and the monohydrate CoSO4·H2O (CAS 13455-34-0, MW 173), the heptahydrate being the standard battery-precursor grade [S2][S4]. Heptahydrate is a red-brown crystalline powder with specific gravity 1.948, bulk density 900 kg/m³, density 2.03 g/mL at 25°C, melting point 96.8-98°C, boiling point 735°C, and water solubility 362 g/L at 20°C [S2][S3][S4]. It dehydrates to the anhydrous salt at 420°C and carries pH 4 at 100 g/L in water, so mild acid-handling applies [S2][S4].
Storage condition from the same spec sheet is +5°C to +30°C in a dry place, with shelf life 1 year and no-caking guarantee, parameters that line up with the Hubei supplier's documented 1-year shelf life and dry-store requirement [S2][S4]. Mono-grade is a pink powder freely soluble in water, used in feed dilutions, paint driers, and pigments [S2].
Grade split: feed, technical, electroplating, battery
Feed grade is locked to HG/T 3775-2005 with Co ≥33% (mono) or ≥20% (hepta), Pb ≤0.002% / 0.001%, As ≤0.0005%, Cd/Mg/Ca not separately capped, and ≥95% fineness through 280μm and 800μm sieves [S1]. It is used as a vitamin B12 precursor, mixing evenly into premix and stored dry away from toxic substances [S1].
Technical and electroplating grades diverge sharply on trace metal ceilings. One supplier's 21% Co / 33% Co / 10% Co tier sheets put battery-grade Ni, Pb, As, Cd, Sb, Hg at 10 ppm max each, with water-insoluble matter ≤0.05% and ≥95% through 100 mesh [S2]. The industrial 21%-Co spec from a second supplier tightens further to Ni 0.001% max, Fe 0.0005% max, Cu 0.0005% max, Mn 0.0005% max, Zn 0.0005% max, Na 0.001% max, Cd 0.0002% max, Pb 0.0001% max, a 100× tighter Pb ceiling than feed grade [S5]. Battery-grade Heptahydrate (CAS 10026-24-1, HS 28332990) is explicitly marketed for lithium-ion precursor synthesis with 21% Co and ≥99% purity [S7].
Application pull: batteries, ceramics, paint driers, feed, electroplating
End uses map cleanly onto grade: battery precursors pull 21% Co heptahydrate with 10 ppm-class Ni/Pb/As/Cd; paint driers and ceramic glazes accept 33% Co monohydrate technical grade; electroplating bath makeup tolerates 20.5-21% Co with tight Cu/Zn/Fe control; feed uses 20-33% Co dilutions under HG/T 3775-2005 [S1][S2][S4][S7]. The supplier's application line "batteries, pigments, ceramics, animal feed" mirrors the same four segments, with HS code 28332990 confirming the customs heading for sulfate-class cobalt salts [S4].
Process-engineering note: a flow meter on the dissolution skid and a pressure transmitter on the crystallization loop are the two instruments most plants standardise when bringing a new cobalt sulfate mother-liquor train online, since CoSO4·7H2O saturation is steep near 20°C and pump head must hold without cavitation. Procurement teams running parallel lithium lines can carry over much of the same precursor-sourcing playbook, including contract structure, port logistics, and grade ladders, as detailed in this lithium hydroxide procurement spec map.
Supplier landscape, capacity, and packaging
The Chinese supply base clusters in Hubei and Hebei, with Hubei Tao Yuan Chemical (Gedian Development Zone, Ezhou) posting 100,000 mt/year nameplate capacity, 30 supply-chain partners, 9-year export history, and primary markets in Southeast Asia, Mideast, and West Asia [S4]. Average lead time is within 15 working days in both peak and off-season, with payment via T/T, LC, Western Union, PayPal, and small-amount channels [S4].
Smaller Hebei-origin resellers run much lower volumes; one paints-drier and energy-storage-focused exporter publishes 100 mt/month output, 25 kg net bags, ISO/FDA certifications, and a Co content band of 20.5% or 21% with 1-year no-caking shelf life [S2][S5]. Xiangtan Swallow Chemicals focuses on the feed-grade niche, offering 25 kg/barrel or 25 kg/bag with custom diluent levels per customer demand [S1]. For adjacent battery-metal sourcing the procurement discipline is similar, as covered in this lithium carbonate 2026 grade gates and sourcing map.
Spec comparison: feed vs technical vs electroplating vs battery
Across the four grades, Co content steps 20-21% (heptahydrate) to 33% (monohydrate technical), and trace-metal ceilings drop by an order of magnitude or more as you move from feed to battery: Pb ≤0.002% in feed vs ≤10 ppm in battery, As ≤0.0005% in feed vs ≤10 ppm in battery, and Cd, Ni, Hg added as named battery controls with 10 ppm ceilings [S1][S2]. The electroplating grade in [S5] tightens Pb further to 0.0001% max and Cd to 0.0002% max, reflecting the residue-on-surface sensitivity of decorative plating. Water-insoluble matter ≤0.05% and ≥95% through 100 mesh are the two mechanical-handling guarantees that recurred across two independent supplier sheets [S2][S4].
Packaging converges on 25 kg as the de facto standard bag, with 50 kg drums and 1,000 kg jumbo bags as the volume options; shelf life 1 year, dry storage, and no-caking are repeated contractual language [S2][S4][S5]. Fineness testing differs by grade: feed checks ≥95% pass through 280 μm and 800 μm sieves under HG/T 3775-2005 [S1], while technical-grade checks ≥95% pass through 100 mesh (≈150 μm) [S2].
Procurement gates: Incoterms, MOQ, lead time, payment
The Hubei supplier quotes MOQ 1 ton and lead time within 15 workdays year-round, with peak-season slack explicitly equal to off-season, an unusual stability that matters when a buyer's pressure sensor on a precursor tank must be calibrated against a predictable delivery slot [S4]. Payment terms span T/T, LC, Western Union, PayPal, and small-amount rails, with Incoterms FOB, CIF, CFR, EXW from Tianjin, Shanghai, and Guangzhou ports [S4]. Average supplier response time ≤4.87h on the same listing sets a service benchmark worth carrying into RFQ scoring [S4].
For smaller-volume industrial buyers, Hebei resellers offer 25 kg bag and 25 kg/barrel options with quoted production capacities around 100 mt/month, but their listed reference prices are negotiable rather than fixed [S1][S2][S5]. A practical three-step gate sequence: (1) lock grade spec by Co% and impurity ceiling, (2) confirm CAS 10026-24-1 (hepta) or 13455-34-0 (mono) plus EINECS 600-050-9, (3) match Incoterm and HS 28332990 to your import declaration before issuing the PO [S4].
Failure modes, storage, and handling
Cobalt sulfate heptahydrate effloresces slowly in dry air and dehydrates fully at 420°C, so storage above +30°C or below +5°C risks both caking and phase change [S2][S4]. The pH-4 mother liquor is mildly acidic; standard 304 stainless is borderline for hot concentrated solutions, so 316L or lined tanks are the safer choice for crystallization loops where industrial valve seats see repeated thermal cycling. Lead and arsenic carry-over from feed-grade material into a battery precursor line is the most common cross-grade contamination event, so most buyers physically separate feed and technical batches in the warehouse and demand lot-specific COA on every shipment [S1][S2].
Trackable next signals: the EU Battery Regulation's due-diligence rules on cobalt continue to push buyers toward ISO- and RMI-audited supply chains, and Chinese producers are responding with RMI-aligned declarations and COA-level impurity breakdowns on a per-lot basis. Watch for the 10 ppm battery-grade Ni/Pb/As/Cd ceilings migrating into more technical-grade sheets as well, which would compress the historical price gap between technical and battery lots.