Why can't Mond publish the biological paper?
The answer to this question is found in Chapter 12.
I would say that it is not that Mond can't publish the paper -- what is going on is that he will not publish it. He could if he wanted to, but he does not want to.
The problem with the paper is that it contains ideas that will upset and destabilize society. Their society is based on the idea that happiness is the highest good and that people should want only to be happy. The paper somehow (we do not know how) implies that there is or should be some other purpose to life.
The paper would encourage people to think more rather than just doing things for fun. That would be bad for society and so Mond is not willing to publish the paper.