This is the only proposal I've seen regarding ocean acidification.

In brief, we need massive amounts of lime to dump into the ocean as an artificial carbon cycle. The problem is how to get lime? If we have massive amounts of clean power, something similar to the cement process (CaCO3 -> CaO) is possible because limestone is cheap.

The problem is the energy requirements are insane. One of the estimations in the talk that remediates only 10% of our yearly CO2 emissions requires 700 TWh (2.52E18 J). Unless we start building \several hundred new GW-scale nuclear[1] power plants (and started a decade ago), I doubt we will be able to do much to address ocean acidification.

[1] I know solar has improved a lot recently. Unless it's possible to generate >1TW of continuous power (24x7), nuclear is probably the only option.

We're only really acidifying the very top layer, unfortunately that's where a huge fraction of the stuff that matters is.

Artificial upwelling is a somewhat promising geo-engineering tech to reduce acidification and increase primary production (and thereby carbon capture). The idea is to somehow bring deep sea water up to the surface. Early attempts used long tubes with one way valves that were lifted up and down by wave energy. New more promising techniques use wave energy to compress air, pump the air down deep and then bubble it (and the surrounding water) up from a grid of pipes.