The home captain batted for almost the entire innings as he finished with 136 in a massive 318 for five total at the De Beers Diamond Oval.
In response, Neil McKenzie hit 72 and Alviro Petersen 62 with the visitors constantly thwarted by wickets at key points and two interruptions during their chase -- the first for rain and the second after a floodlight failure.
Their initial target was first revised to 308 (47 overs) and then brought down to 269 (40 overs), but they could only manage 259 for eight.
Having won the toss and batted first, Van Wyk led from the front and batted for 48.2 overs to help his side to an imposing total.
Almost every batsmen got starts with Reeza Hendricks (16) putting on 34 for the first wicket before he was sent on his way by Ethan O'Reilly.
Rilee Rossouw (14) joined his skipper and helped take the score to 73, before he became the first of Jean Symes’ two wickets.
Van Wyk crossed his 50 from 58 balls, shortly before taking the Free Staters beyond the 100 mark.
Along with Dean Elgar, they put on 98 together -- the biggest partnership of the innings - with Symes eventually achieving the breakthrough when he had the left-hander caught on the deep mid-wicket boundary by Aaron Phangiso for 48.
But the wicket hardly stemmed the momentum as Obus Pienaar (35) shared in another half-century stand with the captain.
They put on 63 together with Van Wyk moving to his 100 in 122 balls.
And after sharing in a third 50-plus stand with Ryan Bailey (59 off 37), his 144-ball knock came to an end, with his partner finishing unbeaten on 47 from 30.
In reply, the Lions lost Gulam Bodi (six) shortly before a rain delay.
But once they resumed, Petersen and Jonathan Vandiar put on 76 together with their stand ended by Michael Erlank, who bowled the latter for 32.
The captain was then joined by McKenzie as they tried valiantly to maintain the run-rate during a 61-run stand which left them needing 158 from 21.1 overs by the time Petersen departed with the score on 150.
A floodlight failure then revised the target even further and the quick wickets of Quinton de Kock (11) and Symes (20) stifled the Lions’ progress even further.
Cliffe Deacon tried his best to pull off the win with 19 from seven balls, including three sixes, but it was not enough as the visitors slipped to a fourth successive loss of the season.