Chloride at 8000 mg/L Is What Kills Catalysts: Inside the A40 Precious-Metal Grade

Ask why a catalytic ozone stage lost performance after six months and the answer is often not the organics. It is the chloride. In high-salinity tail water, chloride complexes onto precious-metal active sites and quietly takes them out of service, and because the water still looks the same, the plant usually blames the ozone generator first. By the time the media is sampled, activity is down by more than 30% and the replacement bill is already approved.

KLE-HEC-200-A40 exists because of that failure mode. It is the high-loading grade in SINOKLE's precious-metal series, carrying more metal than the A20 model and adding a second cerium protective layer, and it is aimed squarely at low-concentration tail water at COD < 200 mg/L where salinity and chloride are the real constraints.

What is different inside the granule

The carrier is a porous inorganic composite prepared by segmented gradient temperature-controlled sintering followed by high-loading atomic-deposition precious-metal composite loading. Specific surface area exceeds 250 m2/g, and the surface carries a high density of transition-metal plus platinum-palladium precious-metal sites. On top sits a double-layer CeO2 anti-chloride passivation barrier.

The higher metal loading lowers the activation energy for ozone decomposition further than the A20 grade does, and radical generation efficiency is correspondingly better — oxidation efficiency runs 3–5 times that of ordinary silica-alumina catalysts. For trace antibiotics, halogenated hydrocarbons, trace humic acid and dye residues, that means stable aromatic rings and long-chain organics are broken completely and mineralised to CO2 and H2O, with the B/C ratio pushed above 0.35. The double cerium layer is what stops chloride occupying the precious-metal sites, and the atomically deposited super-hydrophilic surface is what stops colloids, oil and suspended solids from scaling the micropores shut.

Specification

• Form: red-gray mixed-color spherical particles, 2–4 mm, customisable.
• Carrier: porous inorganic composite with high-loading transition metal plus precious metal dual active components.
• Strength: compressive strength ≥1 MPa (single-particle compression ≥100 N), annual wear rate ≤0.3%.
• Pore structure: pore volume ≥0.3ml/g, specific surface area >250 m2/g, bulk density 0.7t/m3.
• pH window: 3–11.
• Performance: ozone decomposition utilisation ≥99%; comprehensive removal ≥70% at influent COD < 200 mg; colour removal ≥98%.
• Life: >5 years, with multiple acid-wash regenerations.
• Duty: biochemical tailwater upgrading, reclaimed water reuse, high-chlorine low-concentration toxic waste liquid, 24 h continuous systems.

Three projects

Landfill leachate to surface-water Class IV

After two-stage MBR biochemical treatment, leachate effluent sat at COD 120–180 mg/L with residual trace humus and high colour, and the site wanted Class IV reuse. At 90 mg/L ozone, 4.5 g/L catalyst and 28 min hydraulic retention, the catalytic unit held effluent at ≤50 mg/L with colour down to within 3 times. Nanofiltration organic load dropped sharply, the membrane cleaning interval doubled, and the site reached full on-site reuse with zero external discharge.

High-chlorine pesticide tail water

A pesticide producer's combined wastewater, after A/O treatment, came out at COD 150–190 mg/L with chloride as high as 8000 mg/L and chlorinated intermediates still present — the condition where conventional catalysts fail fastest. At 110 mg/L ozone, 5.5 g/L catalyst and 32 min retention, chlorinated toxic intermediate removal was 98%, effluent COD held below 50 mg/L, and B/C rose to 0.38. After a year of continuous running there was no obvious activity decay.

Pharmaceutical API park

Combined biochemical effluent from several API manufacturers, COD 130–170 mg/L, mixed with trace bacteriostatic antibiotics and toxic enough that it could not be reused for equipment cleaning. At 100 mg/L ozone, 5 g/L catalyst and 30 min retention, trace antibiotics were fully degraded, toxicity was largely eliminated, and effluent COD stabilised at 40–50 mg/L — good enough for workshop equipment rinsing and floor cleaning, which saved over a million yuan a year in fresh water.

How it compares with A20

The A20 grade is the economical choice and does the same job in cleaner water. A40 changes three things: metal loading is higher, so removal of trace residual matter is better and COD removal at equal ozone dosage runs 10%–20% above conventional precious-metal catalysts; the anti-chlorine structure is double rather than single layer, which is what held activity decay to 5% after 360 days in high-salinity high-chlorine water against the >30% typical of ordinary media; and regeneration is more durable — acid washing restores over 95% of performance and can be repeated more than three times, stretching the replacement cycle to 8–10 years. Purchase price is higher, but the combination of ozone utilisation ≥99%, low media loss and a long regeneration cycle makes the medium-term total lower.

Process and delivery

The standard high-chlorine configuration is two-stage CDFU cyclonic dissolved-air flotation for suspended solids, emulsified oil and high-salinity impurities, feeding CDOF ozone catalytic oxidation charged with A40, all skid-mounted and factory prefabricated so an existing station can be retrofitted without stopping production. For park reuse duty the train adds quartz sand deep filtration, with online COD, ozone concentration, pH and chloride content driving automatic adjustment of dosing, air-water backwashing and slag discharge under remote monitoring.

The system runs fully enclosed and pressurised with tail-gas ozone destruction, so there is no odour and no toxic gas release; civil investment is low because skid equipment replaces concrete; and because the process needs no bulk flocculent or decolourant, chemical sludge drops by more than 70% with no heavy-metal or precious-metal leaching. SINOKLE holds high-tech, specialised-innovation, ISO three-system and more than twenty invention-patent qualifications, and provides water testing, process customisation, installation, commissioning, catalyst regeneration and annual inspection from one team. Extended duties include dyeing and leather tail water, petrochemical refining effluent, power and metallurgy circulating blowdown, and VOC absorption liquor.