Impregnated and precursor-matched carbon for mercury, lead, arsenic and chromium — a chemistry problem in which pH and speciation decide everything.
The same metal at two pH values is two different removal problems.
Arsenic as arsenite behaves nothing like arsenate; chromium as the trivalent cation behaves nothing like chromate. Each form has its own charge, its own affinity and its own optimum pH window, and the plant only removes what the surface can actually bind. This is why a heavy metals proposal always starts with the speciation analysis and a pH profile, not with a carbon grade.
90–99
% metal removal
Typical removal on a correctly speciated stream with a matched grade.
The carbon is one stage in a train, not the whole of it.
The metals are identified by species and oxidation state, not by total concentration, and the pH profile of the stream is recorded across normal operation.
Candidate media are tested on the actual stream, because competing ions and complexing agents in a real matrix change capacity by an order of magnitude.
The stream is conditioned into the window the chosen chemistry needs, and the bed is sized for the contact time that binding requires at that pH.
Spent media are handled as metal-bearing waste and routed to licensed recovery or disposal, with the route confirmed before the installation is commissioned.
The grades that fit heavy metal removal — and what each is good at.
Elemental sulphur on shell base
The established mercury grade in both liquid and vapour duty, binding mercury as a stable sulphide rather than holding it by physical adsorption.
Iron oxide on carbon base
Developed for arsenic, where iron sites bind arsenate strongly within a controlled pH window and hold it against typical background ions.
Low ash · low leachable
The unimpregnated base for metals that respond to a clean, high-surface carbon, and for duties where the impregnant itself would be a contaminant.
What each property actually governs once the bed is running.
The chemistry that actually binds the metal. It is selected against the species present and is the primary specification decision.
Sets the speciation and the surface charge together. Outside the declared window, capacity falls away regardless of the media condition.
Established by testing on the actual water. Published capacities from single-metal solutions overstate what a real matrix will deliver.
Binding kinetics are slower than organic adsorption, and the required residence rises as the target outlet concentration falls.
Finer cuts shorten the diffusion path to the binding sites and improve outlet quality where the target is at trace level.
What the media itself can release. It matters in potable duty and it determines the classification of the spent material.
Only weakly, and unreliably. Carbon is an excellent adsorbent for organics, but most dissolved metals need a surface chemistry that binds them specifically. That is what impregnation provides, and it is why metal duty is specified on impregnant rather than on iodine number.
Because it sets both the species the metal exists as and the charge on the media surface. Arsenic, chromium and several other metals shift form across the normal pH range, and each form has a different affinity. A grade that works at one pH can fail entirely at another.
By testing on the actual stream. Published capacities are generated from clean single-metal solutions, and a real water containing competing ions, organic complexing agents and variable pH will deliver considerably less.
It becomes a metal-bearing waste and goes to licensed recovery or disposal. For mercury in particular, the route and the associated cost are established before commissioning, because they materially affect the operating economics.
Sometimes, where their chemistries overlap and a single pH window suits all of them. More often the metals present pull in different directions, and either staged beds or a pH-conditioning step between them is the honest answer.
Send the speciation analysis, the pH profile and the outlet target, and we will come back with the media, the contact time and the disposal route to plan for.
